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Ordering number : EN5776
Monolithic Linear IC
LA8638V
Low-voltage Compander IC for Cordless Telephones
Overview
The LA8638V provides dynamic range expansion, noise suppression for enhancing the quality of audio signals in cordless telephones and other communications systems. This single chip provides the functions that make it ideal for cordless telephones: a compressor with a logarithmic compression ratio of 1/2, expander with a logarithmic expansion ratio of 2, splatter filter, microphone amplifier, BTL amplifier, waveform shaper for the receiving signal, muting for both receiving and transmitting signals, and standby operation.
speaker with a load of 2 k * Standby operation that conserves battery power during intermittent reception by disabling all but the waveform shaper for the receiving signal * Built-in splatter filter with user-specified fc * Low-voltage operation (1.8 V to 5.5 V)
Package Dimensions
unit: mm 3191-SSOP30
[LA8638V]
Functions
* Transmitter circuits: compressor, microphone amplifier, limiter (IDC), muting, output level changes to userspecified levels, and splatter filter * Receiver circuits: expander, buffer amplifier for filters, muting, output level changes to user-specified levels, and BTL amplifier * Other circuits: waveform shaper for the receiving signal and standby operation
Features
* Full processing of baseband signals for both receiving and transmitting signals * Built-in BTL receiver amplifier for driving a ceramic
SANYO: SSOP30
Specifications
Maximum Ratings at Ta = 25C
Parameter Maximum power supply voltage Maximum power dissipation Operating temperature Storage temperature Symbol VCC max Pd max Topr Tstg Ta 75C Conditions Ratings 7.0 100 -20 to +75 -40 to +125 Unit V mW C C
Operating Conditions at Ta = 25C
Parameter Recommended power supply voltage Operating power supply voltage range Symbol VCC VCCop Conditions Ratings 2.4 1.8 to 5.5 Unit V V
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40398RM (OT) No. 5776-1/16
LA8638V Electrical Characteristics at Ta = 25C, VCC = 2.4 V, fIN = 1 kHz
Parameter Current drain with no signal Standby current Symbol ICCO ISTBY VOc GCc GEc THDc VNOc VLT VG max Lalt ATTc CTc fIN = 5 kHz; fifth-order Butterworth function filter (fc = 3.35 kHz) VIN = +30 dB, 1 kHz BPF RX--VIN = -10 dBV, 1 kHz BPF VIN = Vinrefe = 0 dB VIN = 0 dB VIN = -30 dB Rg = 620 , f = 20 to 20 kHz VIN = +10 dB, 1 kHz BPF TX--VIN = -40 dBV, 1 kHz BPF THD = 3% VIN = -5 dBV 43 -39.0 2.2 3.2 -18.8 6.0 -1.5 No signal Standby mode, No signal Conditions Ratings min 3.0 0.4 typ 5.4 0.7 max 7.6 0.95 Unit mA mA
[Transmitter block] Vinrefc = -60 dBV = 0 dB, microphone amplifier gain = 40 dB, RL = 15 k Output level Gain change level Gain error Total harmonic distortion Output noise voltage Limiting voltage Microphone amplifier maximum voltage gain Low pass filter attenuation Muting attenuation Crosstalk level VIN = Vinrefc = 0 dB VIN = -10 dB VIN = -40 dB VIN = 0 dB Rg = 620, f = 20 to 20 kHz VIN = +30 dB, 1 kHz BPF 0.88 40 12.0 -18.1 3.5 -2.0 -16.1 4.0 -0.7 0.45 1.8 1.05 46 16.5 -83 -61 25.0 -65 -50 -14.1 4.4 +1.0 1.0 4.5 1.23 dBV dB dB % mVrms Vp-p dB dB dBV dBV
[Receiver block] Vinrefe = -20 dBV = 0 dB, RL = 15 k Output level Gain change level Gain error Output noise voltage Muting attenuation Crosstalk level [BTL amplifier] RL = 2 k Maximum output voltage Total harmonic distortion [Data shaper] VIN = -20 dBV, RL = 100 k Duty factor Dead zone Output "H" level Output "L" level [Digital input characteristics] Input "H" level 1 Input "L" level 1 Input "H" level 2 Input "L" level 2 VIH1 VIL2 VIH2 VIL2 Pins 17, 18, 20, and 22 Pins 17, 18, 20, and 22 Pin 19 Pin 19 1.3 0.3 0.6 VCC 0.25 VCC V V V V DUTY UNSN VH VL 50 -34.5 2.38 0.12 0.3 57 -30.0 % dBV V V VObtl THDbtl 4.2 0.4 1.0 Vp-p % VOe GCe GEe VNOe ATTe CTe -16.3 7.1 +0.3 50 -100 -83 -13.8 8.4 +2.0 100 -80 -65 dBV dB dB Vrms dBV dBV
No. 5776-2/16
LA8638V Block Diagram
No. 5776-3/16
LA8638V Sample Application Circuit
No. 5776-4/16
LA8638V Test Circuit
No. 5776-5/16
LA8638V Usage Notes 1. Internal Reference Voltages The chip uses the following reference voltages internally. Pin 29 (VREF) Power supply voltage follower (approximately 0.5 VCC) Pin 4 (VREF2) Fixed voltage (approximately 1.25 V) 2. Microphone Amplifier Do not use the microphone amplifier as a buffer amplifier (non-reversing, zero-gain amplifier) because it is designed for high-gain operation--that is, gains above 6 dB--and is susceptible to oscillation below that level. For proper circuit balance, use the same resistance value for the bias resistor (between pins 28 and 29) and the feedback resistor (between pins 26 and 27). 3. BTL Amplifier The built-in BTL amplifier is designed for ceramic speakers only. Do not use it to drive a dynamic speaker. 4. Receiver Input Filter The receiver input filter uses external capacitors and resistors to determine the cutoff frequencies. The external circuit constants may be easily derived from the standardized circuit constants. Start by making all resistors the same size and determine the capacitances required to achieve the desired cutoff frequencies from the circuit constants in Table 1. Then, because capacitors are not available for such precise values, choose the closest ones available and then finetune the resistances. (As a result, the final resistances will not necessarily be equal.) Once the filter constants have been established, choose the bias voltage supply resistor RB so that the total DC resistance between pins 4 and 5 is on the order of 120 k to standardize the voltage drop across this path due to the small base current from the transistor in the pin 5 input circuit and thus the duty factor for the data shaper at the next stage.
Table 1. Standardized Circuit Constants Lowpass filter type Second-order Butterworth function Third-order Butterworth function Second-order Bessel function Third-order Bessel function X1 0.7071 0.2025 0.5000 0.1451 X2 1.4142 3.5468 0.6667 0.8136 X3 -- 1.3926 -- 0.5647
The Bessel functions for cutoff frequencies do not incorporate the notion of 3dB attenuation. The 3-dB attenuation frequency for the second-order function is 1.38 fc; for the third-order function, 1.75 fc.
5. Splatter Filter Cutoff Frequency The resistance between pin 24 and ground determines the cutoff frequency for the splatter filter in the transmitter circuit. (See Graph 1 on p. 8.) To fine-tune this frequency, use two resistors and adjust them to achieve the desired frequency. 6. Gain Change Levels The resistance between pins 29 and 30 determines the gain change level for the transmitter circuits. (See Graph 2 on p. 8.) The resistance between pin 9 and ground determines the gain change level for the receiver circuits. (See Graph 3 on p. 8.)
No. 5776-6/16
LA8638V 7. Protective Diodes Preventing Static Breakdown The control pins and data output pins have had their upper protective diodes removed so as to permit direct connection to a microcomputer. No protective diodes: VCC (pin 15), GND (pins 1 and 12) Lower protective diodes only: Pins 16 to 20, 22 Both upper and lower protective diodes: All other pins 8. Preemphasis and Deemphasis This chip provides preemphasis in the microphone amplifier and deemphasis in the BTL amplifier's input stage. The amount depends on the CR time constants for the filters on the corresponding pins--the primary high pass filter on the microphone amplifier's positive (pin 28) or negative (pin 27) input for preemphasis and the primary low pass filter between pins 10 and 11 for deemphasis. 9. Full-Wave Rectifier Smoothing Capacitors The external capacitors on pins 8 and 25 are for the full-wave rectifiers for the expander and compressor. They not only smooth the output but also determine the time constant for the transient characteristics. This time constant is the product of the capacitance and 15 k, the input resistance of the full-wave rectifier. Although there is a tendency to lower the time constant for the expander to reduce noise at the ends of words, the designer must keep in mind that such cuts reduce the amount of smoothing and thus raise the risk of distortion. 10. Compressor's Summing Amplifier Achieving a DC gain of 1 and an AC gain of infinity from the compressor's summing amplifier requires suppressing AC feedback with the capacitor on pin 3. The cutoff frequency is determined by the product of its capacitance and the internal resistance of 22.5 k. 11. Standby Function The chip's standby function does not produce a total shutdown of all circuits. It disables the audio signal processing block, but leaves the waveform shaper block for the receiving signal operating. For this reason, it is not possible to connect the battery directly to the power supply pin (pin 15). There must be an intervening transistor switch for an intermittent power supply. 12. Control Modes
Pin 17 SUB-CNT1 OPEN/HIGH OPEN/HIGH LOW LOW Pin Number Pin 19 Pin 20 Pin 22 Pin 18 SUB-CNT2 OPEN/HIGH LOW OPEN/HIGH LOW Pin Name BTL-CNT TX-MUTE TX-LVL-CNT Mode Standby Receiver muted Normal receiver output levels Low receiver output levels OPEN/HIGH BTL amplifier disabled Transmitter muted Normal transmitter output levels LOW BTL amplifier enabled Transmitter enabled High transmitter output levels
Note: The standby mode overrides all other mode settings.
No. 5776-7/16
LA8638V
Graph 1. Splatter Filter Cutoff Frequency vs. External Resistance
Graph 2. Transmitter Gain Change Level vs. External Resistance
Cutoff frequency (kHz)
External resistance (k) Graph 3. Receiver Gain Change Level vs. External Resistance
Level difference (dB)
External resistance (k)
Level difference (dB)
External resistance (k)
No. 5776-8/16
LA8638V Pin Descriptions
Pin Number 1 Pin Name GND Pin Voltage Equivalent Circuit Description Ground for all circuits except BTL amplifier
2
1/2 VCC
VCC/2
Resistance voltage divider pin
29
VREF
VCC/2
Reference voltage for all circuits except receiver block
3
CMP-NF
VCC/2
AC feedback control for compressor's summing amplifier DC gain: 1 AC gain: Infinite
4
DT-VREF
1.25 V
Reference voltage for receiver block This supplies the bias voltage for pin 5.
5
RX-IN
1.25 V power supply
Filter buffer input
6
RX-FIL-OUT
1.25 V
Filter buffer output
7
EXP-IN
VCC/2
Expander input. Voltage-current converter input. Full-wave rectifier input.
8
EXP-RCT
Indeterminate (when there is no signal)
Full-wave rectifier output for expander block (AC smoothing)
9
RX-ATT-ADJ
0.03 V
Pin for setting attenuation for receiver output level switching
10
RX-OUT
VCC/2
Receiver block output
Continued on next page.
No. 5776-9/16
LA8638V
Continued from preceding page.
Pin Number 12 Pin Name BTL-GND Pin Voltage Equivalent Circuit Description Ground for BTL amplifier
11
BTL-IN
VCC/2
BTL amplifier input
13
BTL-OUT1
VCC/2
BTL amplifier reversed output
14
BTL-OUT2
VCC/2
BTL amplifier non-reversed output
15
VCC
Power supply pin
16
FSK-OUT
Indeterminate (when there is no signal)
Comparator output (open collector output)
17 18 20 22
SUB-CNT1 SUB-CNT2 TX-MUTE TX-LVL-CNT
VCC VCC VCC VCC Internal operating mode control pins. All four have identical structures.
19
BTL-CNT
VCC + 0.65 ---------- 2
BTL amplifier operation control pins
21
TX-DATA-IN
VCC /1.6
Transmitter data input
23
TX-OUT
VCC /1.6
Transmitter output
24
FREQ-ADJ
0.01 V
Pin for setting cutoff frequency of splatter filter
Continued on next page.
No. 5776-10/16
LA8638V
Continued from preceding page.
Pin Number Pin Name Pin Voltage Equivalent Circuit Description
25
CMP-RCT
Indeterminate (when there is no signal)
Full-wave rectifier output for compressor block (AC smoothing)
26 27 28
MIC-OUT MIC-IN2 MIC-IN1
VCC/2 VCC/2 VCC/2 power supply
Microphone amplifier output Microphone amplifier negative input Microphone amplifier positive input
30
TX-LVL-ADj
VCC/2
Pin for setting amplification for transmitter output level switching
I/O Characteristics
Crosstalk Characteristics
Output level, VO -- dBV
O
UT
TX
-O
(p
U
pi T(
n2
in
23
3)
Crosstalk level, CT -- dBV
RX TX
(pin 23)
)
TX-MUT
E (pin 23
)
TX -D
-OU T( pin
10)
T-
TX RX (pin 10)
RX
RX-MUTE (pin
10)
Input level, VIN -- dBV
Splatter Filter Frequency Characteristics VCC = 2.4 V; resistance
Input level, VIN -- dBV
Current Drain --. VCC
BTL on
Current drain, ICC -- mA
Response -- dB
BTL off
Standby
Frequency, f -- kHz
Power supply voltage, VCC -- V
No. 5776-11/16
LA8638V
Output Level -- VCC Gain Change Level Difference -- VCC
TX (pin 23) VIN = -60 dBV
RX (pin 10) VIN = -20 dBV
Gain change level difference, GC -- dB
Output level, VO -- dBV
Switches gain between high and low levels. Resistance at pin 9: 1 k; Resistance between pins 30 and 29: 4.7 k
Power Supply Voltage, -- VCC V
Compander Gain Error -- VCC
Power supply voltage, VCC -- V
Output Distortion -- VCC
Total harmonic distortion, THD -- %
Compander gain error, GE -- dB
RX (pin 10) VIN = -20 dBV TX (pin 23) VIN = -60 dBV
TX-DATA (pin 23) VIN = -20 dBV
Power supply voltage, VCC -- V
BTL Power Amplifier Maximum Output Voltage -- VCC
Power supply voltage, VCC -- V
Receiver Muting Attenuation -- VCC
Maximum output voltage, VO -- Vp-p
Muting level -- dBV
Pins 13 and 14
Pin 10
Power supply voltage, VCC -- V
Receiver (TX RX) Crosstalk -- VCC 1 kHz-BPF TX-IN(28 pin): VIN = -40dBV
Power supply voltage, VCC -- V Transmitter Crosstalk -- VCC
Crosstalk level, CT -- dBV
Pin 13
Pin 10 Pin 14
Power supply voltage, VCC -- V
Crosstalk level, CT -- dBV
Power supply voltage, VCC -- V No. 5776-12/16
LA8638V
Output Noise Level -- VCC Splatter Filter Cutoff Frequency -- VCC Att. = 3 dB down; resistance at pin 24 = 4.3 k
Output noise level -- dBV
TX (pin 23)
TX (pin 23)
Power supply voltage, VCC -- V
Splatter Filter Attenuation -- VCC fIN = 5 or 1 kHz; resistance at pin 24 = 4.3 k
Cutoff frequency -- kHz
TX (pin 23)
Power supply voltage, VCC -- V
Data Shaper Duty Cycle -- VCC
Attenuation -- dB
Power supply voltage, VCC -- V
Data Shaper Dead Zone -- VCC No signal
Duty cycle -- %
Power supply voltage, VCC -- V
Current Drain -- Ta BTL on
Minimum input level -- dBV
Current drain, ICC -- mA
BTL off
Standby
Power supply voltage, VCC -- V
Output Level -- Ta
Ambient temperature, Ta -- C Gain Change Level Difference -- Ta
RX (pin 10) VIN = -20 dBV TX (pin 23) VIN = -60 dBV
Gain change level difference, GC -- dB
Output level, VO -- dBV
TX-DATA (pin 23) VIN = -20 dBV
Switches gain between high and low levels. Resistance at pin 9: 1 k; Resistance between pins 30 and 29: 4.7 k
Ambient temperature, Ta -- C
Ambient temperature, Ta -- C
No. 5776-13/16
LA8638V
Compander Gain Error -- Temperature Output Distortion -- Temperature
Total harmonic distortion, THD -- %
Compander gain error, GE -- dB
TX (pin 23) V{IN} = -60 dBV RX (pin 10) V{IN} = -20 dBV
Ambient temperature, Ta -- C
BTL Distortion -- Temperature
Ambient temperature, Ta -- C
BTL Power Amplifier Maximum Output Voltage -- Temperature THD output = 1 %
Total harmonic distortion, THD -- %
Pin 13 Pin 14
Ambient temperature, Ta -- C
BTL Output Level -- Temperature
Maximum output voltage, VO -- VPP
Ambient temperature, Ta -- C
Receiver Muting Attenuation -- Temperature
Pin 14
Output level, VO -- dBV
Muting level -- dBV
Pin 13
Pin 13 Pin 14
Pin 10
Ambient temperature, Ta -- C
Receiver (TX RX) Crosstalk -- Temperature
Ambient temperature, Ta -- C
Transmitter Crosstalk -- Temperature
Crosstalk level, CT -- dBV
Pin 13
Pin 10
Pin 14
Ambient temperature, Ta -- C
Crosstalk level, CT -- dBV
Ambient temperature, Ta -- C No. 5776-14/16
LA8638V
Output Noise Level -- Temperature Splatter Filter Cutoff Frequency -- Temperature Att. = 3 dB down; resistance at pin 24 = 4.3 k
Output noise level -- dBV
TX (pin 23)
TX-MUTE (pin 23)
RX (pin 10) RX-MUTE (pin 10)
Ambient temperature, Ta -- C
Splatter Filter Attenuation -- Temperature
Cutoff frequency -- kHz
Ambient temperature, Ta -- C
Receiver Maximum Input Level -- Temperature
Ambient temperature, Ta -- C
Transmitter Maximum Input Level -- Temperature THD = 1% for output from pin 23
Maximum inputlevel at pin 5 -- dBV
THD = 1% for output from pin 10
Attenuation -- dB
Ambient temperature, Ta -- C
Data Shaper Duty Cycle -- Temperature
Maximum input level at pin 21 -- dBV
Ambient temperature, Ta -- C
Data Shaper Dead Zone -- Temperature
Duty cycle -- %
Ambient temperature, Ta -- C
Minimum input level -- dBV
Ambient temperature, Ta -- C No. 5776-15/16
LA8638V
s No products described or contained herein are intended for use in surgical implants, life-support systems, aerospace equipment, nuclear power control systems, vehicles, disaster/crime-prevention equipment and the like, the failure of which may directly or indirectly cause injury, death or property loss. s Anyone purchasing any products described or contained herein for an above-mentioned use shall: Accept full responsibility and indemnify and defend SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors and all their officers and employees, jointly and severally, against any and all claims and litigation and all damages, cost and expenses associated with such use: Not impose any responsibility for any fault or negligence which may be cited in any such claim or litigation on SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors or any of their officers and employees jointly or severally. s Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied regarding its use or any infringements of intellectual property rights or other rights of third parties. This catalog provides information as of April, 1998. Specifications and information herein are subject to change without notice. PS No. 5776-16/16

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