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19-3134; Rev 0; 5/04
1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers
General Description
The MAX9770 combines a mono, filterless, Class D speaker amplifier and stereo DirectDrive headphone amplifiers in a single device. The MAX9770 operates from a single 2.5V to 5.5V supply and includes features that reduce external component count, system cost, board space, and offer improved audio reproduction. The speaker amplifier makes use of Maxim's patented Class D architecture, providing Class AB performance with Class D efficiency, conserving board space, and extending battery life. The speaker amplifier delivers 1.2W into an 8 load while offering efficiencies above 85%. A spread-spectrum scheme reduces radiated emissions caused by the modulation frequency. Furthermore, the MAX9770 oscillator can be synchronized to an external clock through the SYNC input, avoiding possible problem frequencies inside a system. The speaker amplifier features a low 0.025% THD+N, high 70dB PSRR, and SNR in excess of 90dB. The headphone amplifiers feature Maxim's patented DirectDrive architecture that produces a ground-referenced output from a single supply, eliminating the need for large DC-blocking capacitors. The headphone amplifiers deliver up to 80mW into a 16 load, feature low 0.015% THD+N, high 80dB PSRR, and 8kV ESD-protected outputs. A headphone sense input detects the presence of a headphone, and automatically configures the amplifiers for either speaker or headphone mode. The MAX9770 includes internally set, logic-selectable gain, and a comprehensive input multiplexer/mixer, allowing multiple audio sources to be selected and for true mono reproduction of a stereo source in speaker mode. Industry-leading click-and-pop suppression eliminates audible transients during power and shutdown cycles. A low-power shutdown mode decreases supply current consumption to 0.1A, further extending battery life. The MAX9770 is offered in space-saving, thermally efficient 28-pin TQFN (5mm x 5mm x 0.8mm) and 28-pin TSSOP packages. The MAX9770 features thermal-overload and output short-circuit protection, and is specified over the extended -40C to +85C temperature range.
Features
1.2W Filterless Class D Amplifier Passes FCC Class B Radiated Emissions Standards with 100mm of Cable Unique Spread-Spectrum Mode Offers 5dB Emissions Improvement Over Conventional Methods 80mW DirectDrive Headphone Amplifier Eliminates Bulky DC-Blocking Capacitors High 80dB PSRR at 217Hz 85% Efficiency Low 0.015% THD+N Industry-Leading Click-and-Pop Suppression Integrated 3-Way Input Mixer/Multiplexer Logic-Selectable Gain Short-Circuit and Thermal Protection 8kV ESD-Protected Headphone Outputs Low-Power Shutdown Mode Available in Space-Saving, Thermally Efficient Packages 28-Pin TQFN (5mm x 5mm x 0.8mm) 28-Pin TSSOP
MAX9770
Ordering Information
PART MAX9770ETI MAX9770EUI
Lead-free package.
TEMP RANGE -40oC to +85oC -40oC to +85oC
PIN-PACKAGE 28 TQFN-EP* 28 TSSOP
*EP = Exposed paddle.
Simplified Block Diagram
VDD DirectDrive STEREO HEADPHONE
L1IN L2IN MONO
Applications
Cellular Phones PDAs Compact Notebooks
R1IN R2IN GAIN SEL INPUT SEL MUTE SHDN HPS CLASS D SPKR (MONO)
MAX9770
Pin Configuration appears at end of data sheet. ________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
ABSOLUTE MAXIMUM RATINGS
GND to PGND to CPGND......................................-0.3V to +0.3V VDD to PVDD to CPVDD..........................................-0.3V to +0.3V VDD to GND..............................................................................6V PVDD to PGND .........................................................................6V CPVDD to CPGND ....................................................................6V CPVSS to CPGND....................................................................-6V SVSS to GND ...........................................................................-6V C1N..........................................(PVSS - 0.3V) to (CPGND + 0.3V) HPOUT_ to GND ....................................................................3V All other pins to GND..................................-0.3V to (VDD + 0.3V) Continuous Current Into/Out of: PVDD, PGND, OUT_ ......................................................600mA PVSS ..............................................................................260mA Duration of HPOUT_ Short Circuit to VDD, PVDD, GND, PGND ...........................................................Continuous Duration of Short Circuit between HPOUTL and HPOUTR ..........................................Continuous Duration of OUT_ Short Circuit to VDD, PVDD, GND, PGND ..10s Duration of Short Circuit Between OUT+ and OUT-...............10s Continuous Power Dissipation (TA = +70C) 28-Pin TQFN (derate 20.8mW/C above +70C) .......1667mW 28-Pin TSSOP (derate 12.8mWC above +70C) ......1026mW Junction Temperature ......................................................+150C Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDD = PVDD = CPVDD = 3.3V, GND = PGND = CPGND = 0V, SHDN = 3.3V, C1 = C2 = 1F, CBIAS = 0.047F, SYNC = GND, RL = , speaker load connected between OUT+ and OUT-, headphone load connected between HPOUT_ and GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2)
PARAMETER GENERAL Supply Voltage Range Quiescent Supply Current Shutdown Supply Current Shutdown to Full Operation Input Impedance Bias Voltage Feedthrough VDD IDD ISHDN tON RIN VBIAS From any unselected input to any output, f = 10kHz VOS VDD = 2.5V to 5.5V Power-Supply Rejection Ratio PSRR (Note 4) VRIPPLE = 200mVP-P, f = 217Hz VRIPPLE = 200mVP-P, f = 1kHz VRIPPLE = 200mVP-P, f = 20kHz f = 1kHz, THD+N = 1%, GAIN1 = 1, GAIN2 = 0 VDD = 3.3V VDD = 5V RL = 8 RL = 4 RL = 8 50 (Note 3) MONO INL_, INR_ 7 14 1.1 Inferred from PSRR test No load SHDN = HPS = GND Headphone mode Speaker mode 2.5 5.5 5.2 0.1 50 10 20 1.25 70 1.4 5.5 10 7.5 10 V mA A ms k V dB SYMBOL CONDITIONS MIN TYP MAX UNITS
SPEAKER AMPLIFIER (GAIN1 = GAIN2 = VDD, HPS = GND) Output Offset Voltage 15 70 70 68 50 550 900 1200 0.025 0.03 % mW dB 70 mV
Output Power
POUT
Total Harmonic Distortion Plus Noise
THD+N
RL = 8, POUT = 300mW, f = 1kHz RL = 4, POUT = 300mW, f = 1kHz
2
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(VDD = PVDD = CPVDD = 3.3V, GND = PGND = CPGND = 0V, SHDN = 3.3V, C1 = C2 = 1F, CBIAS = 0.047F, SYNC = GND, RL = , speaker load connected between OUT+ and OUT-, headphone load connected between HPOUT_ and GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2)
PARAMETER Signal-to-Noise Ratio SYMBOL SNR SYNC = GND Output Switching Frequency FS SYNC = FLOAT SYNC = VDD SYNC Frequency Lock Range Efficiency PO = 1000mW, f = 1kHz GAIN1 = 0, GAIN2 = 0 Gain AV GAIN1 = 0, GAIN2 = 1 GAIN1 = 1, GAIN2 = 0 GAIN1 = 1, GAIN2 = 1 Gain Accuracy Speaker Path Off-Isolation HPS = VDD, headphone amplifier active, f = 1kHz VOS VDD = 2.5V to 5.5V Power-Supply Rejection Ratio PSRR (Note 3) VRIPPLE = 200mVP-P, f = 217kHz VRIPPLE = 200mVP-P, f = 1kHz VRIPPLE = 200mVP-P, f = 20kHz f = 1kHz, THD+N = 1% VDD = 3.3V VDD = 5V Total Harmonic Distortion Plus Noise Signal-to-Noise Ratio Crosstalk Headphone Off-Isolation THD+N SNR RL = 32 RL = 16 RL = 32 RL = 16 40 65 102 800 85 6 3 9 0 5 % dB dB CONDITIONS RL = 8, VOUT = 2VRMS, A-weighted 980 1280 MIN TYP 85.9 1100 1450 1220 120kHz 2000 kHz % 1220 1620 kHz MAX UNITS dB
MAX9770
HEADPHONE AMPLIFIER (GAIN1 = 1, GAIN2 = 0, HPS = VDD ) Output Offset Voltage 5 76 85 82 56 55 40 60 80 0.015 0.03 101 80 96 % dB dB dB mW dB 10 mV
Output Power
POUT
RL = 32, POUT = 50mW, f = 1kHz RL = 16, POUT = 35mW, f = 1kHz RL = 32, VOUT = 300mVRMS, BW = 22Hz to 22kHz Between channels, f = 1kHz, VIN = 200mVP-P HPS = GND, speaker amplifier active, f = 1kHz
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3
1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
ELECTRICAL CHARACTERISTICS (continued)
(VDD = PVDD = CPVDD = 3.3V, GND = PGND = CPGND = 0V, SHDN = 3.3V, C1 = C2 = 1F, CBIAS = 0.047F, SYNC = GND, RL = , speaker load connected between OUT+ and OUT-, headphone load connected between HPOUT_ and GND, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Notes 1, 2)
PARAMETER Capacitive-Load Drive SYMBOL CL GAIN1 = 0, GAIN2 = 0 Gain AV GAIN1 = 0, GAIN2 = 1 GAIN1 = 1, GAIN2 = 0 GAIN1 = 1, GAIN2 = 1 Gain Accuracy ESD Protection Input Voltage High Input Voltage Low Input Leakage Current HPS Input Current VIH VIL SYNC input All other logic inputs HPS = GND HPOUTR, HPOUTL, IEC Air Discharge 2 0.8 25 1 -10 8 DIGITAL INPUTS (SHDN, SYNC, HPS, GAIN_, SEL_) V V A A CONDITIONS MIN TYP 1000 7 4 -2 1 2.5 % kV dB MAX UNITS pF
Note 1: All devices are 100% production tested at +25C. All temperature limits are guaranteed by design. Note 2: Speaker amplifier testing performed with a resistive load in series with an inductor to simulate an actual speaker load. For RL = 4, L = 47H. For RL = 8, L = 68H. Note 3: Guaranteed by design, not production tested. Note 4: PSRR is specified with the amplifier inputs connected to GND through CIN.
Typical Operating Characteristics
(VDD = 3.3V, BW = 22Hz to 22kHz, GAIN1 = 1, GAIN2 = 0, spread-spectrum mode, headphone outputs in phase.)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (SPEAKER MODE)
MAX9770 toc01
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (SPEAKER MODE)
MAX9770 toc02
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (SPEAKER MODE)
RL = 8
MAX9770 toc03
10 VDD = +5V RL = 4 1 THD+N (%) POUT = 25mW 0.1
10 RL = 4
10
1 THD+N (%) THD+N (%) POUT = 100mW 0.1
1 POUT = 40mW 0.1
0.01
POUT = 1000mW
0.01
POUT = 500mW
0.01
POUT = 400mW
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
4
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Typical Operating Characteristics (continued)
(VDD = 3.3V, BW = 22Hz to 22kHz, GAIN1 = 1, GAIN2 = 0, spread-spectrum mode, headphone outputs in phase.)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (SPEAKER MODE)
MAX9770 toc04
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (SPEAKER MODE)
MAX9770 toc05
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (SPEAKER MODE)
RL = 4 10
MAX9770 toc06
10 VDD = 5V POUT = 1W RL = 8 1 THD+N (%)
100 VDD = 5V RL = 8 10
100
THD+N (%)
1 f = 1kHz 0.1 f = 20Hz
THD+N (%)
1 f = 1kHz f = 20Hz 0.1
0.1
SSM MODE
0.01
FFM MODE
0.01 0.001
f = 10kHz
0.01 0.001
f = 10kHz
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0
400
800
1200
1600
0
200
OUTPUT POWER (mW)
800 600 400 OUTPUT POWER (mW)
1000
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (SPEAKER MODE)
MAX9770 toc07
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (SPEAKER MODE)
MAX9770 toc08
OUTPUT POWER vs. LOAD RESISTANCE (SPEAKER MODE)
1.50 OUTPUT POWER (W) 1.25 1.00 0.75 0.50 0.25 0 THD+N = 1% VDD = 5V f = 1kHz THD+N = 10%
MAX9770 toc09
100 RL = 8 10
100 VDD = 5V f = 1kHz RL = 8
1.75
10
THD+N (%)
1 f = 20Hz
THD+N (%)
f = 1kHz
1 SSM MODE 0.1
0.1
0.01 f = 10kHz 0.001 0 200 400 600 800 OUTPUT POWER (mW)
0.01 FFM MODE 0.001 0 400 800 1200 1600 OUTPUT POWER (mW)
1
10 LOAD RESISTANCE ()
100
OUTPUT POWER vs. LOAD RESISTANCE (SPEAKER MODE)
MAX9770 toc10
OUTPUT POWER vs. SUPPLY VOLTAGE (SPEAKER MODE)
f = 1kHz RL = 8 THD+N = 10% OUTPUT POWER (W) 1.5 EFFICIENCY (%)
MAX9770 toc11
EFFICIENCY vs. OUTPUT POWER
90 80 70 60 50 40 30 20 10 VDD = 5V f = 1kHz RL = 8 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
MAX9770 toc12
1.0 f = 1kHz 0.8 OUTPUT POWER (W) THD+N = 10% 0.6
2.0
100
1.0
0.4 THD+N = 1% 0.2
0.5
THD+N = 1%
0 1 10 LOAD RESISTANCE () 100
0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V)
0 OUTPUT POWER (W)
_______________________________________________________________________________________
5
1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Typical Operating Characteristics (continued)
(VDD = 3.3V, BW = 22Hz to 22kHz, GAIN1 = 1, GAIN2 = 0, spread-spectrum mode, headphone outputs in phase.)
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY (SPEAKER MODE)
MAX9770 toc13 MAX9770 toc14
EFFICIENCY vs. OUTPUT POWER
100 90 80 EFFICIENCY (%) 70 PSRR (dB) 60 50 40 30 20 10 0 0 0.2 0.4 0.6 0.8 1.0 OUTPUT POWER (W) f = 1kHz RL = 4 RL = 8 0 -10 -20 -30 -40 -50 -60 -70 -80 10
OUTPUT SPECTRUM (SPEAKER MODE)
RL = 8 f = 1kHz FFM MODE VIN = -60dBV
MAX9770 toc15
0 -20 MAGNITUDE (dB) -40 -60 -80 -100 -120 -140
VRIPPLE = 200mVP-P RL = 8
100
1k FREQUENCY (Hz)
10k
100k
0
5
15 10 FREQUENCY (kHz)
20
OUTPUT SPECTRUM (SPEAKER MODE)
MAX9770 toc16
OUTPUT SPECTRUM (SPEAKER MODE)
MAX9770 toc17
WIDEBAND OUTPUT SPECTRUM (SPEAKER MODE)
-10 -20 MAGNITUDE (dB) -30 -40 -50 -60 -70 -80 -90 -100 FFM MODE RBW = 10kHz
MAX9770 toc18
0 -20 MAGNITUDE (dB) -40 -60 -80 -100 -120 -140 0 5 15 10 FREQUENCY (kHz) RL = 8 f = 1kHz SSM MODE VIN = -60dBV
0 -20 -40 MAGNITUDE (dB) -60 -80 -100 -120 -140 -160 RL = 8 f = 1kHz SSM MODE A-WEIGHTED VIN = -60dBV
0
20
0
5
15 10 FREQUENCY (kHz)
20
1M
10M FREQUENCY (Hz)
100M
WIDEBAND OUTPUT SPECTRUM (SPEAKER MODE)
-10 -20 MAGNITUDE (dB) -30 -40 -50 -60 -70 -80 -90 -100 1M 10M FREQUENCY (Hz) 100M OUT+ - OUTSSM MODE RBW = 10kHz
MAX9770 toc19
STARTUP WAVEFORM (SPEAKER MODE)
MAX9770 toc20
MIXER OUTPUT
MAX9770 toc21
0
IN_1 SHDN 2V/div IN_2
10kHz 1V/div 4kHz 1V/div
MONO 500mV/div RL = 8 f = 1kHz 4ms/div OUT
1kHz 2V/div
1V/div
400s/div
6
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Typical Operating Characteristics (continued)
(VDD = 3.3V, BW = 22Hz to 22kHz, GAIN1 = 1, GAIN2 = 0, spread-spectrum mode, headphone outputs in phase.)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (HEADPHONE MODE)
MAX9770 toc23
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (HEADPHONE MODE)
MAX9770 toc22
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (HEADPHONE MODE)
RL = 16 1 THD+N (%)
MAX9770 toc24
10 VDD = 5V RL = 16 1 THD+N (%) POUT = 10mW
10 VDD = 5V RL = 32 1 THD+N (%)
10
0.1
0.1
POUT = 10mW
0.1
POUT = 10mW
0.01 POUT = 50mW 0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.01 POUT = 50mW 0.001 10 100 1k FREQUENCY (Hz) 10k 100k
0.01
POUT = 35mW
0.001 10 100 1k FREQUENCY (Hz) 10k 100k
TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (HEADPHONE MODE)
MAX9770 toc25
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (HEADPHONE MODE)
MAX9770 toc26
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (HEADPHONE MODE)
VDD = 5V RL = 32
MAX9770 toc27
10 RL = 32 1 THD+N (%)
100 VDD = 5V RL = 16
100
10
10
THD+N (%)
1 f = 10kHz f = 1kHz 0.1
THD+N (%)
1 f = 1kHz 0.1 f = 10kHz
0.1
POUT = 10mW
0.01 0.01 POUT = 50mW 0.001 10 100 1k FREQUENCY (Hz) 10k 100k f = 20Hz 0.001 0 20 40 60 80 100 OUTPUT POWER (mW) 0.001 0 f = 20Hz 20 40 60 80 0.01
OUTPUT POWER (mW)
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (HEADPHONE MODE)
MAX9770 toc28
TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (HEADPHONE MODE)
RL = 32 10
MAX9770 toc29
OUTPUT POWER vs. LOAD RESISTANCE (HEADPHONE MODE)
90 80 OUTPUT POWER (mW) 70 60 50 40 30 20 THD+N = 1% THD+N = 10% VDD = 5V f = 1kHz
MAX9770 toc30
100 RL = 16 10
100
100
THD+N (%)
1 f = 1kHz 0.1
THD+N (%)
f = 10kHz
1 f = 10kHz 0.1 f = 1kHz
0.01 0.001 0 f = 20Hz 10 20 30 40 50 60
0.01 f = 20Hz 0.001 0 20 40 60 80 OUTPUT POWER (mW)
10 0 10 100 LOAD RESISTANCE () 1000
OUTPUT POWER (mW)
_______________________________________________________________________________________
7
1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Typical Operating Characteristics (continued)
(VDD = 3.3V, BW = 22Hz to 22kHz, GAIN1 = 1, GAIN2 = 0, spread-spectrum mode, headphone outputs in phase.)
OUTPUT POWER vs. LOAD RESISTANCE (HEADPHONE MODE)
MAX9770 toc31
OUTPUT POWER vs. SUPPLY VOLTAGE (HEADPHONE MODE)
MAX9770 toc32
OUTPUT POWER vs. SUPPLY VOLTAGE (HEADPHONE MODE)
70 OUTPUT POWER (mW) 60 50 40 30 20 10 0 THD+N = 1% RL = 32 f = 1kHz THD+N = 10%
MAX9770 toc33
80 f = 1kHz 70 OUTPUT POWER (mW) 60 50 40 30 20 10 0 10 100 LOAD RESISTANCE () THD+N = 10% THD+N = 1%
100 90 80 OUTPUT POWER (mW) 70 60 50 40 30 20 10 0 THD+N = 1% RL = 16 f = 1kHz THD+N = 10%
80
1000
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
POWER DISSIPATION vs. OUTPUT POWER (HEADPHONE MODE)
MAX9770 toc34
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY (HEADPHONE MODE)
MAX9770 toc35
CROSSTALK vs. FREQUENCY (HEADPHONE MODE)
-10 -20 CROSSTALK (dB) -30 -40 -50 -60 -70 -80 -90 -100 RIGHT TO LEFT 10 100 1k FREQUENCY (Hz) 10k 100k LEFT TO RIGHT RL = 32 f = 1kHz VIN = 200mVP-P
MAX9770 toc36
300 250 POWER DISSIPATION (mW) 200 150 100 50 0 0 30 60 90 120 RL = 32 f = 1kHz POUT = POUTL + POUTR RL = 16
0 -10 -20 -30 PSRR (dB) -40 -50 -60 -70 -80 -90 -100 VDD = 5V VRIPPLE = 200mVP-P RL = 32
0
150
10
100
1k FREQUENCY (Hz)
10k
100k
OUTPUT POWER (mW)
FEEDTHROUGH vs. FREQUENCY
MAX9770 toc37
OUTPUT POWER vs. CHARGE-PUMP CAPACITANCE
MAX9770 toc38
OUTPUT SPECTRUM (HEADPHONE MODE)
RL = 32 f = 1kHz VIN = -60dBV
MAX9770 toc39
0 -10 -20 FEEDTHROUGH (dB) -30 -40 -50 -60 -70 -80 -90 -100 10 100 1k FREQUENCY (Hz) 10k SPEAKER MODE HEADPHONE MODE SEL1 = 0 SEL2 = 1 IN1_ = GND IN2_ = DRIVEN VIN = 2VP-P
60 C1 = C2 = 1F 50 OUTPUT POWER (mW) 40 C1 = C2 = 0.47F 30 20 10 0 f = 1kHz THD+N = 1% 20 30 LOAD () 40
0 -20 MAGNITUDE (dB) -40 -60 -80 -100 -120 -140
100k
50
0
5
10 15 FREQUENCY (kHz)
20
8
_______________________________________________________________________________________
1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Typical Operating Characteristics (continued)
(VDD = 3.3V, BW = 22Hz to 22kHz, GAIN1 = 1, GAIN2 = 0, spread-spectrum mode, headphone outputs in phase.)
EXITING SHUTDOWN (HEADPHONE MODE)
MAX9770 toc40
ENTERING SHUTDOWN (HEADPHONE MODE)
MAX9770 toc41
RL = 32 SHDN 2V/div SHDN
RL = 32 2V/div
OUT_
10mV/div
OUT_
10mV/div
2s/div
2s/div
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9770 toc42
SHUTDOWN SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX9770 toc43
10
0.5
SUPPLY CURRENT (mA)
SUPPLY CURRENT (A)
8
SPEAKER MODE
0.4
6 HEADPHONE MODE
0.3
4
0.2
2
0.1
0 2.5 3.5 4.5 5.5 SUPPLY VOLTAGE (V)
0 2.5 3.5 4.5 5.5 SUPPLY VOLTAGE (V)
Pin Description
PIN TQFN 1 2 3 4 5 6 TSSOP 4 5 6 7 8 9 NAME BIAS VDD HPOUTR HPOUTL SVSS HPS FUNCTION Common-Mode Bias Voltage. Bypass with a 0.047F capacitor to GND. Power Supply Right-Channel Headphone Output Left-Channel Headphone Output Headphone Amplifier Negative Power Supply Headphone Sense Input
_______________________________________________________________________________________
9
1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Pin Description (continued)
PIN TQFN 7 8 9 10 11 12 13 14 15 TSSOP 10 11 12 13 14 15 16 17 18 NAME CPVDD CPVSS C1N C1P CPGND SEL1 SEL2 SELM SHDN Positive Charge-Pump Power Supply Charge-Pump Output. Connect to SVSS. Charge-Pump Flying Capacitor Negative Terminal Charge-Pump Flying Capacitor Positive Terminal Charge-Pump Ground Select Stereo Channel 1 Inputs. Digital input. Drive SEL1 high to select inputs IN1_L and IN1_R. Select Stereo Channel 2 Inputs. Digital input. Drive SEL2 high to select inputs IN2_L and IN2_R. Select Mono Channel Input. Digital input. Drive SELM high to select the MONO input. Shutdown. Drive SHDN low to disable the device. Connect SHDN to VDD for normal operation. Frequency Select and External Clock Input. SYNC = GND: fixed-frequency PWM mode with fS = 1100kHz. SYNC = Float: fixed-frequency PWM mode with fS = 1450kHz. SYNC = VDD: spread-spectrum PWM mode with fS = 1220kHz 120kHz. SYNC = Clocked: fixed-frequency PWM mode with fS = external clock frequency. Speaker Amplifier Power Ground Speaker Amplifier Positive Output Speaker Amplifier Negative Output Speaker Amplifier Power Supply Gain Control Input 2 Gain Control Input 1 Mono Channel Input Stereo Channel 2, Left Input Stereo Channel 1, Left Input Ground Stereo Channel 2, Right Input Stereo Channel 1, Right Input Exposed Paddle. Can be left floating or tied to GND. FUNCTION
16
19
SYNC
17 18 19 20 21 22 23 24 25 26 27 28 EP
20 21 22 23 24 25 26 27 28 1 2 3 --
PGND OUT+ OUTPVDD GAIN2 GAIN1 MONO IN2_L IN1_L GND IN2_R IN1_R EP
Detailed Description
The MAX9770 combines a mono 1.2W Class D speaker amplifier and stereo 80mW DirectDrive headphone amplifiers with integrated headphone sensing and comprehensive click-and-pop suppression. A mixer/multiplexer allows for selection and mixing between two stereo input sources and a single mono source. The MAX9770 features a high 80dB PSRR, low 0.015% THD+N, industry-leading click/pop performance, and a low-power shutdown mode.
10
Class D Speaker Amplifier
The MAX9770 Class D amplifier features a true filterless, low EMI, switch-mode architecture that provides Class AB-like performance with Class D efficiency. Comparators monitor the MAX9770 input and compare the input voltage to a sawtooth waveform. The comparators trip when the input magnitude of the sawtooth exceeds the corresponding input voltage. The comparator resets at a fixed time after the rising edge of the second comparator trip point, generating a minimum-
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers
width pulse tON(min) at the output of the second comparator (Figure 1). As the input voltage increases or decreases, the duration of the pulse at one output increases (the first comparator trip point) while the other output pulse duration remains at tON(min). This causes the net voltage across the speaker (VOUT+ VOUT-) to change.
MAX9770
Table 1. Operating Modes
SYNC INPUT GND FLOAT VDD Clocked MODE FFPWM with fS = 1100kHz FFPWM with fS = 1450kHz SSPWM with fS = 1220kHz 120kHz FFPWM with fS = external clock frequency
Operating Modes
The switching frequency of the charge pump is 1/2 the switching frequency of the Class D amplifier, regardless of the operating mode. When SYNC is driven externally, the charge pump switches at 1/2 fSYNC. When SYNC = VDD, the charge pump switches with a spreadspectrum pattern.
Fixed-Frequency Modulation (FFM) Mode The MAX9770 features two FFM modes. The FFM modes are selected by setting SYNC = GND for a 1.1MHz switching frequency, and SYNC = FLOAT for a 1.45MHz switching frequency. In FFM mode, the frequency spectrum of the Class D output consists of the
tSW
VIN-
VIN+
OUT-
OUT+
tON(MIN)
VOUT+ - VOUT-
Figure 1. MAX9770 Outputs with an Input Signal Applied
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
fundamental switching frequency and its associated harmonics (see the Wideband FFT graph in the Typical Operating Characteristics). The MAX9770 allows the switching frequency to be changed by +32% should the frequency of one or more harmonics fall in a sensitive band. This can be done during operation and does not affect audio reproduction. Spread-Spectrum Modulation (SSM) Mode The MAX9770 features a unique, patented spreadspectrum mode that flattens the wideband spectral components, improving EMI emissions radiated by the speaker and cables by 5dB. Proprietary techniques ensure that the cycle-to-cycle variation of the switching period does not degrade audio reproduction or efficiency (see the Typical Operating Characteristics). Select SSM mode by setting SYNC = V DD . In SSM mode, the switching frequency varies randomly by 120kHz around the center frequency (1.22MHz). The modulation scheme remains the same, but the period of the sawtooth waveform changes from cycle-to-cycle (Figure 2). Instead of a large amount of spectral energy present at multiples of the switching frequency, the energy is now spread over a bandwidth that increases with frequency. Above a few MHz, the wideband spectrum looks like white noise for EMI purposes (Figure 3).
tSW
tSW
tSW
tSW
VIN-
VIN+
OUT-
OUT+
tON(MIN)
VOUT+ - VOUT-
Figure 2. MAX9770 Output with an Input Signal Applied (SSM mode)
12
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
50.0 45.0 AMPLITUDE (dBV/m) 40.0 35.0 30.0 25.0 20.0 15.0 10.0 30.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 200.0 220.0 240.0 260.0 280.0 300.0 FREQUENCY (MHz)
Figure 3. MAX9770 EMI with 75mm of Speaker Cable
VIN = 0V
synchronizes the switching frequency of both the Class D and charge pump. The period of the SYNC clock can be randomized, enabling the MAX9770 to be synchronized to another spread-spectrum Class D amplifier operating in SSM mode.
Filterless Modulation/Common-Mode Idle
The MAX9770 uses Maxim's unique, patented modulation scheme that eliminates the LC filter required by traditional Class D amplifiers, improving efficiency, reducing component count, conserving board space and system cost. Conventional Class D amplifiers output a 50% duty cycle square wave when no signal is present. With no filter, the square wave appears across the load as a DC voltage, resulting in finite load current, increasing power consumption. When no signal is present at the device input, the outputs switch as shown in Figure 4. Because the MAX9770 drives the speaker differentially, the two outputs cancel each other, resulting in no net idle mode voltage across the speaker, minimizing power consumption.
OUT-
OUT+
VOUT+ - VOUT- = 0V
Figure 4. MAX9770 Output with No Signal Applied
Efficiency
Efficiency of a Class D amplifier is attributed to the region of operation of the output stage transistors. In a Class D amplifier, the output transistors act as currentsteering switches and consume negligible additional power. Any power loss associated with the Class D output stage is mostly due to the I*R loss of the MOSFET on-resistance, and quiescent current overhead.
External Clock Mode The SYNC input allows the MAX9770 to be synchronized to a system clock (allowing a fully synchronous system), or allocating the spectral components of the switching harmonics to insensitive frequency bands. Applying an external clock of 800kHz to 2MHz to SYNC
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
The theoretical best efficiency of a linear amplifier is 78%; however, that efficiency is only exhibited at peak output powers. Under normal operating levels (typical music reproduction levels), efficiency falls below 30%, whereas the MAX9770 still exhibits >80% efficiencies under the same conditions (Figure 5).
EFFICIENCY (%)
EFFICIENCY vs. OUTPUT POWER
100 90 80 70 60 50 40 30 20 10 0 0 0.1 0.2 0.3 0.4 0.5 0.6 OUTPUT POWER (W) CLASS AB MAX9770
DirectDrive
Traditional single-supply headphone drivers have their outputs biased about a nominal DC voltage (typically half the supply) for maximum dynamic range. Large coupling capacitors are needed to block this DC bias from the headphone. Without these capacitors, a significant amount of DC current flows to the headphone, resulting in unnecessary power dissipation and possible damage to both headphone and headphone driver. Maxim's patented DirectDrive architecture uses a charge pump to create an internal negative supply voltage. This allows the headphone outputs of the MAX9770 to be biased about GND, almost doubling dynamic range while operating from a single supply. With no DC component, there is no need for the large DC-blocking capacitors. Instead of two large (220F, typ) tantalum capacitors, the MAX9770 charge pump requires two small ceramic capacitors, conserving board space, reducing cost, and improving the frequency response of the headphone driver. See the Output Power vs. ChargePump Capacitance and Load Resistance graph in the Typical Operating Characteristics for details of the possible capacitor sizes. There is a low DC voltage on the driver outputs due to amplifier offset. However, the offset of the MAX9770 is typically 5mV, which, when combined with a 32 load, results in less than 160A of DC current flow to the headphones. In addition to the cost and size disadvantages of the DCblocking capacitors required by conventional headphone amplifiers, these capacitors limit the amplifier's low-frequency response and can distort the audio signal. Previous attempts at eliminating the output-coupling capacitors involved biasing the headphone return (sleeve) to the DC bias voltage of the headphone amplifiers. This method raises some issues: 1) When combining a microphone and headphone on a single connector, the microphone bias scheme typically requires a 0V reference. 2) The sleeve is typically grounded to the chassis. Using the midrail biasing approach, the sleeve must be isolated from system ground, complicating product design. 3) During an ESD strike, the driver's ESD structures are the only path to system ground. Thus, the driver must be able to withstand the full ESD strike.
14
VDD = 3.3V f = 1kHz RL - 8
Figure 5. MAX9770 Efficiency vs. Class AB Efficiency
4) When using the headphone jack as a line out to other equipment, the bias voltage on the sleeve may conflict with the ground potential from other equipment, resulting in possible damage to the drivers. Charge Pump The MAX9770 features a low-noise charge pump. The switching frequency of the charge pump is 1/2 the switching frequency of the Class D amplifier, regardless of the operating mode. When SYNC is driven externally, the charge pump switches at 1/2 fSYNC. When SYNC = VDD, the charge pump switches with a spread-spectrum pattern. The nominal switching frequency is well beyond the audio range, and thus does not interfere with the audio signals, resulting in an SNR of 101dB. The switch drivers feature a controlled switching speed that minimizes noise generated by turn-on and turn-off transients. By limiting the switching speed of the charge pump, the di/dt noise caused by the parasitic bond wire and trace inductance is minimized. Although not typically required, additional high-frequency noise attenuation can be achieved by increasing the size of C2 (see Typical Application Circuit). The charge pump is active in both speaker and headphone modes.
Input Multiplexer/Mixer
The MAX9770 features an input multiplexer/mixer that allows three different audio sources to be selected/ mixed. Driving a SEL_ input high selects the input channel (see Table 2), and the audio signal is output to the active amplifier. When a stereo path is selected in speaker mode (SEL1 or SEL2 = 1), the left and right
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Table 2. Multiplexer/Mixer Settings
SEL1 0 1 0 0 1 1 0 1 SEL2 SELM 0 0 1 0 1 0 1 1 0 0 0 1 0 1 1 1 MUTE IN1_L IN2_L MONO (IN1_L + IN2_L) / 2 (IN1_L + MONO) /2 (IN2_L + MONO) / 2 (IN1_L + IN2_L + MONO) / 3 HEADPHONE MODE HPOUTL MUTE IN1_R IN2_R MONO (IN1_R + IN2_R) / 2 (IN1_R + MONO) / 2 (IN2_R + MONO) / 2 (IN1_R + IN2_R + MONO) / 3 HPOUTR MUTE (IN1_L + IN1_R) / 2 (IN2_L + IN2_R) / 2 MONO (IN1_L + IN1_R + IN2_L + IN2_R) / 4 (IN1_L + IN1_R + MONO x 2) / 4 (IN2_L + IN2_R + MONO x 2) / 4 (IN1_L + IN1_R + IN2_L + IN2_R + MONO x 2) / 6 SPEAKER MODE
inputs are attenuated by 6dB and mixed together, resulting in a true mono reproduction of a stereo signal. When more than one signal path is selected, the sources are attenuated before mixing to preserve overall amplitude. Selecting two sources results in 6dB attenuation, selecting three sources results in 9.5dB attenuation.
VDD MAX9770 800k SHUTDOWN CONTROL HPS HPOUTL HPOUTR 10k 10k
Headphone Sense Input (HPS)
The headphone sense input (HPS) monitors the headphone jack, and automatically configures the device based upon the voltage applied at HPS. A voltage of less than 0.8V sets the device to speaker mode. A voltage of greater than 2V disables the bridge amplifiers and enables the headphone amplifiers. For automatic headphone detection, connect HPS to the control pin of a 3-wire headphone jack as shown in Figure 6. With no headphone present, the output impedance of the headphone amplifier pulls HPS to less than 0.8V. When a headphone plug is inserted into the jack, the control pin is disconnected from the tip contact and HPS is pulled to VDD through the internal 800k pullup. When driving HPS from an external logic source, ground HPS when the MAX9770 is shut down. Place a 10k resistor in series with HPS and the headphone jack to ensure 8kV ESD protection. Table 2 shows the output amplitude of the selected channels multiplied by the gain.
Figure 6. HPS Configuration
Gain Selection
The MAX9770 features a logic-selectable, internally set gain. GAIN1 and GAIN2 set the gain of the MAX9770 speaker and headphone amplifiers as shown in Table 3. The MAX9770 can be configured to automatically switch between two gain settings depending on whether the device is in speaker or headphone mode. By driving one or both gain inputs with HPS, the gain of the device changes when a headphone is inserted or removed. For example, the block diagram shows HPS connected to GAIN2, while GAIN1 is connected to VDD. In this configuration, the gain in speaker mode is 9dB, while the gain in headphone mode is 1dB. The gain settings with the HPS connection are shown in Table 4.
15
BIAS
The MAX9770 features an internally generated, powersupply independent, common-mode bias voltage referenced to GND. BIAS provides both click-and-pop suppression and sets the DC bias level for the amplifiers. Choose the value of the bypass capacitor as described in the BIAS Capacitor section. No external load should be applied to BIAS. Any load lowers the BIAS voltage, affecting the overall performance of the device.
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Table 3. Gain Selection
SPEAKER GAIN (dB) HEADPHONE GAIN (dB) SPEAKER OUTPUT POWER (VIN = 0.707VRMS) (mW) 500 / 4 250 / 4 500 / 8 124 / 4 SPEAKER OUTPUT POWER (VIN = 1VRMS) (mW) 500 / 8 500 / 4 1000 / 8 250 / 4 HEADPHONE OUTPUT POWER (VIN = 0.707VRMS) (mW) 60* / 32 78 / 16 19 / 16 39 / 16 HEADPHONE OUTPUT POWER (VIN = 1VRMS) (mW) 60* / 32 60* / 32 39 / 16 78 / 16
GAIN1
GAIN2
0 0 1 1
0 1 0 1
6 3 9 0
7 4 -2 1
*Output power limited to 60mW due to output voltage swing.
Table 4. Gain Settings with HPS Connection
GAIN1 HPS HPS 0 1 HPS 0 0 1 1 GAIN2 0 1 HPS HPS HPS 0 1 0 1 SPEAKER MODE GAIN (HPS = 0) 6 3 6 9 6 6 3 9 0 HEADPHONE MODE GAIN (HPS = 1) -2 1 4 1 1 7 4 -2 1
Headphone Amplifier In conventional single-supply headphone drivers, the output-coupling capacitor is a major contributor of audible clicks and pops. Upon startup, the driver charges the coupling capacitor to its bias voltage, typically half the supply. Likewise, during shutdown, the capacitor is discharged to GND. This results in a DC shift across the capacitor, which in turn, appears as an audible transient at the speaker. Since the MAX9770 headphone amplifier does not require output-coupling capacitors, this does not arise. Additionally, the MAX9770 features extensive click-andpop suppression that eliminates any audible transient sources internal to the device. The Power-Up/PowerDown Waveform in the Typical Operating Characteristics shows that there are minimal spectral components in the audible range at the output upon startup or shutdown. In most applications, the output of the preamplifier driving the MAX9770 has a DC bias of typically half the supply. During startup, the input-coupling capacitor is charged to the preamplifier's DC bias voltage through the RF of the MAX9770, resulting in a DC shift across the capacitor and an audible click/pop. An internal delay of 50ms eliminates the click/pop caused by the input filter.
Shutdown
The MAX9770 features a 0.1A, low-power shutdown mode that reduces quiescent current consumption and extends battery life. Drive SHDN low to disable the drive amplifiers, bias circuitry, and charge pump. Bias is driven to GND and the headphone amplifier output impedance is 10k in shutdown. Connect SHDN to VDD for normal operation.
Applications Information
Filterless Operation
Traditional Class D amplifiers require an output filter to recover the audio signal from the amplifier's output. The filters add cost, increase the solution size of the amplifier, and can decrease efficiency. The traditional PWM scheme uses large differential output swings (2 x VDD peak-to-peak) at idle and causes large ripple currents. Any parasitic resistance in the filter components results in a loss of power, lowering efficiency.
Click-and-Pop Suppression
Speaker Amplifier The MAX9770 speaker amplifier features comprehensive click-and-pop suppression that eliminates audible transients on startup and shutdown. While in shutdown, the H-bridge is in a high-impedance state. During startup or power-up, the input amplifiers are muted and an internal loop sets the modulator bias voltages to the correct levels, preventing clicks and pops when the H-bridge is subsequently enabled. For 30ms following startup, a soft-start function gradually unmutes the input amplifiers.
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers
The MAX9770 does not require an output filter. The device relies on the inherent inductance of the speaker coil and the natural filtering of both the speaker and the human ear to recover the audio component of the square-wave output. Eliminating the output filter results in a smaller, less costly, and more efficient solution. Because the frequency of the MAX9770 output is well beyond the bandwidth of most speakers, voice coil movement due to the square-wave frequency is minimal. Although this movement is small, a speaker not designed to handle the additional power may be damaged. For optimum results, use a speaker with a series inductance >10H. Typical small 8 speakers exhibit series inductances in the range of 20H to 100H. removes the DC bias from an incoming signal (see the Typical Application Circuit). The AC-coupling capacitor allows the amplifier to bias the signal to an optimum DC level. Assuming zero-source impedance, the -3dB point of the highpass filter is given by: f-3dB = 1 2RINCIN
MAX9770
Output Offset
Unlike Class AB amplifiers, the output offset voltage of a Class D amplifier does not noticeably increase quiescent current draw when a load is applied. This is due to the power conversion of the Class D amplifier. For example, a 15mV DC offset across an 8 load results in 1.9mA extra current consumption in a Class AB device. In the Class D case, a 15mV offset into 8 equates to an additional power drain of 28W. Due to the high efficiency of the Class D amplifier, this represents an additional quiescent current draw of 28W/(VDD / 100 x ), which is on the order of a few microamps.
RIN is the amplifier's internal input resistance value given in the Electrical Characteristics. Be aware that the MONO input has a higher input impedance than the other inputs. Choose CIN such that f-3dB is below the lowest frequency of interest. Setting f -3dB too high affects the amplifier's low-frequency response. Setting f-3dB too low can affect the click-and-pop performance. Use capacitors with low-voltage coefficient dielectrics, such as tantalum or aluminum electrolytic. Capacitors with high-voltage coefficients, such as ceramics, may result in increased distortion at low frequencies. Output Filter The MAX9770 speaker amplifier does not require an output filter for normal operation and audio reproduction. The device passes FCC Class B radiated emissions standards with 100mm of unshielded speaker cables. However, output filtering can be used if a design is failing radiated emissions due to board layout or cable length, or if the circuit is near EMI-sensitive devices. Use a common-mode choke connected in series with the speaker outputs if board space is limited and emissions are a concern. Use of an LC filter is necessary if excessive speaker cable is used. BIAS Capacitor BIAS is the output of the internally generated DC bias voltage. The BIAS bypass capacitor, CBIAS improves PSRR and THD+N by reducing power supply and other noise sources at the common-mode bias node, and also generates the clickless/popless, startup/shutdown DC bias waveforms for the speaker amplifiers. Bypass BIAS with a 0.047F capacitor to GND. Large values of CBIAS result in poor click/pop performance, and smaller values of CBIAS result in degradation of PSRR and increased output noise.
Power Supplies
The MAX9770 has different supplies for each portion of the device, allowing for the optimum combination of headroom and power dissipation and noise immunity. The speaker amplifiers are powered from PVDD. PVDD ranges from 2.5V to 5.5V. The headphone amplifiers are powered from VDD and SVSS. VDD is the positive supply of the headphone amplifiers and ranges from 2.5V to 5.5V. SVSS is the negative supply of the headphone amplifiers. Connect SVSS to CPVSS. The charge pump is powered by CPVDD. CPVDD ranges from 2.5V to 5.5V and should be the same potential as VDD. The charge pump inverts the voltage at CPVDD, and the resulting voltage appears at CPVSS. The remainder of the device is powered by VDD.
Component Selection
Input Filter The input capacitor (CIN), in conjunction with the amplifier input resistance (RIN), forms a highpass filter that
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Table 5. Suggested Capacitor Manufacturers
SUPPLIER Taiyo Yuden TDK PHONE 800-348-2496 807-803-6100 FAX 847-925-0899 847-390-4405 WEBSITE www.t-yuden.com www.component.tdk.com
Charge-Pump Capacitor Selection Use capacitors with an ESR less than 100m for optimum performance. Low-ESR ceramic capacitors minimize the output resistance of the charge pump. Most surface-mount ceramic capacitors satisfy the ESR requirement. For best performance over the extended temperature range, select capacitors with an X7R dielectric. Table 5 lists suggested manufacturers. Flying Capacitor (C1) The value of the flying capacitor (C1) affects the load regulation and output resistance of the charge pump. A C1 value that is too small degrades the device's ability to provide sufficient current drive, which leads to a loss of output voltage. Increasing the value of C1 may improve load regulation and reduces the charge-pump output resistance to an extent. Above 1F, the on-resistance of the switches and the ESR of C1 and C2 dominate. Output Capacitor (C2) The output capacitor value and ESR directly affect the ripple at CPVSS. Increasing the value of C2 reduces output ripple. Likewise, decreasing the ESR of C2 reduces both ripple and output resistance. Lower capacitance values can be used in systems with low maximum output power levels. See the Output Power vs. Charge Pump Capacitance and Load Resistance graph in the Typical Operating Characteristics. CPVDD Bypass Capacitor The CPVDD bypass capacitor (C3) lowers the output impedance of the power supply and reduces the impact of the MAX9770's charge-pump switching transients. Bypass CPVDD with C3, the same value as C1, and place it physically close to the CPVDD and PGND (refer to the MAX9770 EV kit for a suggested layout).
Layout and Grounding
Proper layout and grounding are essential for optimum performance. Use large traces for the power-supply inputs and amplifier outputs to minimize losses due to parasitic trace resistance, as well as route the head away from the device. Good grounding improves audio performance, minimizes crosstalk between channels, and prevents any switching noise from coupling into the audio signal. Connect CPGND, PGND, and GND together at a single point on the PC board. Route CPGND and all traces that carry switching transients away from GND, PGND, and the traces and components in the audio signal path. Connect all components associated with the charge pump (C2 and C3) to the CPGND plane. Connect SVSS and CPVSS together at the device. Place the chargepump capacitors (C1, C2, and C3) as close to the device as possible. Bypass VDD and PVDD with a 1F capacitor to GND. Place the bypass capacitors as close to the device as possible. Use large, low-resistance output traces. As load impedance decreases, the current drawn from the device outputs increase. At higher current, the resistance of the output traces decrease the power delivered to the load. Large output, supply, and GND traces also improve the power dissipation of the device. The MAX9770 thin QFN package features an exposed thermal pad on its underside. This pad lowers the package's thermal resistance by providing a direct heat conduction path. Due to the high efficiency of the MAX9770's Class D amplifier, additional heatsinking is not required. If additional heatsinking is required, connect the exposed paddle to GND. See the MAX9770 EV kit data sheet for suggested component values and layout guidelines.
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Block Diagram
2.5V TO 5.5V
1F VDD 2 (5) VDD CIN 0.47F CIN 0.47F CIN 0.47F CIN 0.47F CIN 0.47F 16 SYNC (19) 25 IN1_L (28) 28 IN1_R (3) 23 MONO (26) 24 IN2_L (27) 27 IN2_R (2) MIXER/ MUX/GAIN CONTROL VDD 20 (23) PVDD 18 (21) OUT+ 19 (22) OUT17 (20) PGND 1 (4) BIAS CBIAS 0.047F
OSCILLATOR CLASS D MODULATOR
2.5V TO 5.5V 0.1F
LEFT-CHANNEL AUDIO INPUT 1 RIGHT-CHANNEL AUDIO INPUT 1 MONO AUDIO INPUT LEFT-CHANNEL AUDIO INPUT 2 RIGHT-CHANNEL AUDIO INPUT 2
H-BRIDGE
21 HPS GAIN2 (24) 22 GAIN1 (25) VDD 14 SELM (17) VDD 12 SEL1 (15) GND 13 SEL2 (16) GND 15 SHDN (18) VDD 7 CPVDD (10) 10 C1P (13) C1 1F C1N 11 CPGND (14) 9 (12)
MUX AND GAIN CONTROL
6 (9) HPS 4 (7) HPOUTL
HEADPHONE DETECTION
SHUTDOWN CONTROL
3 (6) HPOUTR
VDD 1F
MAX9770
CHARGE PUMP OSC/2
8 (11) CPVSS
5 (8) SVSS C2 1F
26 (1) GND
( ) TSSOP PIN.
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
System Diagram
2.5V TO 5.5V
1F
1F
VDD 0.47F IN1_R MP3 DAC IN1_L 0.47F 0.47F IN2_R FM RADIO MODULE 0.47F 0.47F MONO BASEBAND PROCESSOR SHDN SEL1 SEL2 SELM VDD VDD GAIN1 GAIN2 GND PGND
PVDD OUT+ OUT-
MAX9770
HPOUTL HPS HPOUTR
IN2_L CPVSS VSS CPGND C1P 1F C1N CPVDD BIAS 0.047F 2.5V TO 5.5V 1F 1F
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Pin Configurations
TOP VIEW
MONO
IN1_R
IN2_R
IN1_L
IN2_R 2 IN1_R 3 BIAS 4 VDD 5 HPOUTR 6 HPOUTL 7 SVSS 8 HPS 9 CPVDD 10 CPVSS 11 C1N 12 C1P 13 CPGND 14
27 IN2_L 26 MONO 25 GAIN1 24 GAIN2 BIAS VDD HPOUTR HPOUTL SVSS HPS CPVDD
28
27
26
25
24
IN2_L
GND
GND 1
28 IN1_L
23
1 2 3 4 5 6 7 10 11 12 13 14 8 9
22 21 20 19
GAIN1
GAIN2 PVDD OUTOUT+ PGND SYNC SHDN
MAX9770
23 PVDD 22 OUT21 OUT+ 20 PGND 19 SYNC 18 SHDN 17 SELM
MAX9770
18 17 16 15
SEL1
SEL2
15 SEL1
TSSOP
TQFN
CPGND
CPVSS
Chip Information
TRANSISTOR COUNT: 7020 PROCESS: BiCMOS
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SELM
C1N
C1P
16 SEL2
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) QFN THIN.EPS
L
0.15 C A
D2
C L
D
b D2/2
0.10 M C A B
PIN # 1 I.D.
D/2
0.15 C B
k
PIN # 1 I.D. 0.35x45
E/2 E2/2 E (NE-1) X e
C L
E2
k L
DETAIL A
e (ND-1) X e
DETAIL B
e
L1
L
C L
C L
L
e 0.10 C A 0.08 C
e
C
A1
A3
PACKAGE OUTLINE 16, 20, 28, 32, 40L, THIN QFN, 5x5x0.8mm
21-0140
E
1
2
Note: The MAX9770 thin QFN package features an exposed thermal pad on its underside. This pad lowers the package's thermal resistance by providing a direct heat conduction path. Due to the high efficiency of the MAX9770's Class D amplifier, additional heatsinking is not required. The voltage of the exposed paddle is -VDD and it is important that the exposed paddle is NOT connected to the ground plane. It should be either left floating or can be tied to the CPVSS pin. See the MAX9770 EV kit data sheet for suggested component values and layout guidelines.
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1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
MAX9770
COMMON DIMENSIONS PKG. 16L 5x5 20L 5x5 28L 5x5 32L 5x5 40L 5x5 SYMBOL MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. A A1 A3 b D E e k L L1 N ND NE JEDEC 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0 0.02 0.05 0.20 REF. 0 0.02 0.05 0.20 REF. 0 0.02 0.05 0.20 REF. 0 0.02 0.05 0.20 REF. 0 0.05 0.20 REF. PKG. CODES T1655-1 T1655-2 T2055-2 T2055-3 T2055-4 T2855-1 T2855-2 T2855-3 T2855-4 T2855-5 T2855-6 T2855-7 T3255-2 T3255-3 T3255-4 T4055-1
EXPOSED PAD VARIATIONS
D2
MIN. NOM. MAX. MIN.
E2 3.10 3.20 3.10 3.20 3.10 3.20 3.10 3.20 3.10 3.25 2.70 3.25 2.70 2.70 3.25 2.70 3.10 3.10 3.10 3.20 3.35 2.80 3.35 2.80 2.80 3.35 2.80 3.20 3.20 3.20
NOM. MAX. ALLOWED
DOWN BONDS
3.00 3.00 3.00 3.00 3.00 3.15 2.60 3.15 2.60 2.60 3.15 2.60 3.00 3.00 3.00 3.20
3.10 3.20 3.00 3.10 3.20 3.00 3.10 3.20 3.00 3.10 3.20 3.00 3.10 3.25 2.70 3.25 2.70 2.70 3.25 2.70 3.10 3.10 3.10 3.20 3.35 2.80 3.35 2.80 2.80 3.35 2.80 3.20 3.20 3.20 3.00 3.15 2.60 3.15 2.60 2.60 3.15 2.60 3.00 3.00 3.00
0.25 0.30 0.35 0.25 0.30 0.35 0.20 0.25 0.30 0.20 0.25 0.30 0.15 0.20 0.25 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 0.80 BSC. 0.65 BSC. 0.50 BSC. 0.50 BSC. 0.40 BSC. - 0.25 - 0.25 - 0.25 0.35 0.45 0.25 - 0.25 0.30 0.40 0.50 0.45 0.55 0.65 0.45 0.55 0.65 0.30 0.40 0.50 0.40 0.50 0.60 16 4 4 WHHB 20 5 5 WHHC 28 7 7 WHHD-1 32 8 8 WHHD-2 0.30 0.40 0.50 40 10 10 -
NO YES NO YES NO NO NO YES YES NO NO YES NO YES NO YES
3.30 3.40 3.20
3.30 3.40
NOTES: 1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994. 2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES. 3. N IS THE TOTAL NUMBER OF TERMINALS. 4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE. 5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm FROM TERMINAL TIP. 6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY. 7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION. 8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS. 9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT EXPOSED PAD DIMENSION FOR T2855-1, T2855-3 AND T2855-6. 10. WARPAGE SHALL NOT EXCEED 0.10 mm. PACKAGE OUTLINE 16, 20, 28, 32, 40L, THIN QFN, 5x5x0.8mm
21-0140
E
2
2
______________________________________________________________________________________
23
1.2W Low-EMI, Filterless, Mono Class D Amplifier with Stereo DirectDrive Headphone Amplifiers MAX9770
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
TSSOP4.40mm.EPS
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
24 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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