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1.2 MHz DC-DC Step-Up Switching Converter ADP1610
FEATURES
Fully integrated 1.2 A , 0.2 , power switch Pin-selectable 700 kHz or 1.2 MHz PWM frequency 92% efficiency Adjustable output voltage up to 12 V 3% output regulation accuracy Adjustable soft start Input undervoltage lockout MSOP 8-lead package
GENERAL DESCRIPTION
The ADP1610 is a dc-to-dc step-up switching converter with an integrated 1.2 A, 0.2 power switch capable of providing an output voltage as high as 12 V. With a package height of less that 1.1 mm, the ADP1610 is optimal for space-constrained applications such as portable devices or thin film transistor (TFT) liquid crystal displays (LCDs). The ADP1610 operates in pulse-width modulation (PWM) current mode with up to 92% efficiency. Adjustable soft start prevents inrush currents at startup. The pin-selectable switching frequency and PWM current-mode architecture allow excellent transient response, easy noise filtering, and the use of small, cost-saving external inductors and capacitors. The ADP1610 is offered in the Pb-free 8-lead MSOP and operates over the temperature range of -40C to +85C.
APPLICATIONS
TFT LC bias supplies Portable applications Industrial/instrumentation equipment
FUNCTIONAL BLOCK DIAGRAM
COMP
1
IN
6
REF FB 2
ERROR AMP gm BIAS
ADP1610
F/F RAMP GEN COMPARATOR RT 7 SS 8 SD
3
5 SW
RQ S DRIVER
OSC SOFT START CURRENT SENSE AMPLIFIER
4
GND
Figure 1.
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.326.8703 (c) 2004 Analog Devices, Inc. All rights reserved.
04472-001
ADP1610 TABLE OF CONTENTS
Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 4 ESD Caution.................................................................................. 4 Pin Configuration and Function Descriptions............................. 5 Typical Performance Characteristics ............................................. 6 Theory of Operation ...................................................................... 10 Current-Mode PWM Operation .............................................. 10 Frequency Selection ................................................................... 10 Soft Start ...................................................................................... 10 On/Off Control........................................................................... 10 Setting the Output Voltage ........................................................ 10 Choosing the Input and Output Capacitors ........................... 11 Diode Selection........................................................................... 12 Loop Compensation .................................................................. 12 Soft Start Capacitor .................................................................... 13 Application Circuits ................................................................... 13 DC-DC Step-Up Switching Converter with True Shutdown14 TFT LCD Bias Supply ................................................................ 14 Sepic Power Supply .................................................................... 14 Layout Procedure ........................................................................... 15 Outline Dimensions ....................................................................... 16 Ordering Guide .......................................................................... 16
REVISION HISTORY
10/04--Revision 0: Initial Version
Rev. 0 | Page 2 of 16
ADP1610 SPECIFICATIONS
VIN = 3.3 V, TA = -40C to +85C, unless otherwise noted. All limits at temperature extremes are guaranteed by correlation and characterization using standard statistical quality control (SQC), unless otherwise noted. Table 1.
Parameter SUPPLY Input Voltage Quiescent Current Nonswitching State Shutdown Switching State1 OUTPUT Output Voltage Load Regulation Overall Regulation REFERENCE Feedback Voltage Line Regulation ERROR AMPLIFIER Transconductance Voltage Gain FB Input Bias Current SWITCH SW On Resistance SW Leakage Current Peak Current Limit2 OSCILLATOR Oscillator Frequency Maximum Duty Cycle SHUTDOWN Shutdown Input Voltage Low Shutdown Input Voltage High Shutdown Input Bias Current SOFT START SS Charging Current UNDERVOLTAGE LOCKOUT3 UVLO Threshold UVLO Hysteresis Symbol VIN IQ IQSD IQSW VOUT ILOAD = 10 mA to 150 mA, VOUT = 10 V Line, load, temperature VFB VIN = 2.5 V to 5.5 V gm AV I = 1 A VFB = 1.23 V RON ICLSET fOSC DMAX VIL VIH ISD RT = GND RT = IN COMP = open, VFB = 1 V, RT = GND Nonswitching state Switching state VSD = 3.3 V VSS = 0 V VIN rising 2.2 0.49 0.89 78 ISW = 1.0 A VSW = 12 V 1.212 -0.15 VFB = 1.3 V, RT = VIN VSD = 0 V fSW = 1.23 MHz, no load VIN 0.05 3 1.230 1.248 +0.15 Conditions Min 2.5 390 0.01 1 Typ Max 5.5 600 10 2 12 Unit V A A mA V mV/mA % V %/V A/V dB nA 400 20 m A A MHz MHz % V V A A 2.5 V mV
100 60 10 200 0.01 2.0 0.7 1.23 83
0.885 1.6 90 0.6
2.2 0.01 3 2.4 220 1
1 2 3
This parameter specifies the average current while switching internally and with SW (Pin 5) floating. Guaranteed by design and not fully production tested. Guaranteed by characterization.
Rev. 0 | Page 3 of 16
ADP1610 ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter IN, COMP, SD, SS, RT, FB to GND SW to GND RMS SW Pin Current Operating Ambient Temperature Range Operating Junction Temperature Range Storage Temperature Range JA, Two Layers JA, Four Layers Lead Temperature Range (Soldering, 60 s) Rating -0.3 V to +6 V 14 V 1.2 A -40C to +85C -40C to +125C -65C to +150C 206C/W 142C/W 300C
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Absolute maximum ratings apply individually only, not in combination. Unless otherwise specified, all other voltages are referenced to GND.
RC CC VOUT
1
IN
COMP
6
IN
CIN
R1 REF FB
2
ERROR AMP gm BIAS
ADP1610
L1
R2 F/F RAMP GEN VIN 1.2MHz 700kHz SD 3 SS CSS
8 5
SW
D1 VOUT COUT
RQ S COMPARATOR DRIVER
RT
7
OSC
SOFT START
CURRENT SENSE AMPLIFIER GND
04472-002
4
Figure 2. Block Diagram and Typical Application Circuit
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
Rev. 0 | Page 4 of 16
ADP1610 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
COMP 1
8
SS
FB 2 SD 3
ADP1610
TOP VIEW (Not to Scale)
7
RT
04472-003
6
IN
GND 4
5
SW
Figure 3. Pin Configuration
Table 3. Pin Function Descriptions
Pin No. 1 2 3 4 5 6 7 8 Mnemonic COMP FB SD GND SW IN RT SS Description Compensation Input. Connect a series resistor-capacitor network from COMP to GND to compensate the regulator. Output Voltage Feedback Input. Connect a resistive voltage divider from the output voltage to FB to set the regulator output voltage. Shutdown Input. Drive SD low to shut down the regulator; drive SD high to turn it on. Ground. Switching Output. Connect the power inductor from the input voltage to SW and connect the external rectifier from SW to the output voltage to complete the step-up converter. Main Power Supply Input. IN powers the ADP1610 internal circuitry. Connect IN to the input source voltage. Bypass IN to GND with a 10 F or greater capacitor as close to the ADP1610 as possible. Frequency Setting Input. RT controls the switching frequency. Connect RT to GND to program the oscillator to 700 kHz, or connect RT to IN to program it to 1.2 MHz. Soft Start Timing Capacitor Input. A capacitor from SS to GND brings up the output slowly at power-up.
Rev. 0 | Page 5 of 16
ADP1610 TYPICAL PERFORMANCE CHARACTERISTICS
100 90 80 70 VOUT = 10V FSW = 700kHz L = 10H VIN = 5.5V VIN = 3.3V VIN = 2.5V 100 VOUT = 7.5V FSW = 1.2MHz L = 4.7H VIN = 5.5V VIN = 3.3V VIN = 2.5V 90 80
EFFICIENCY (%)
60 50 40 30 20
04472-005
EFFICIENCY (%)
70 60
50
10 0 1 10 100 LOAD CURRENT (mA)
30 1 10 100 LOAD CURRENT (mA)
1000
1000
Figure 4. Output Efficiency vs. Load Current
Figure 7. Output Efficiency vs. Load Current
100 90 80 70 VOUT = 10V F = 1.2MHz L = 4.7H
VIN = 5.5V VIN = 3.3V VIN = 2.5V
2.4
2.2
VIN = 5.5V
CURRENT LIMIT (A)
EFFICIENCY (%)
2.0
VIN = 3.3V
60 50 40 30 20
04472-006
1.8 VIN = 2.5V 1.6
1.4
04472-009
10 0 1 10 100 LOAD CURRENT (mA)
1000
1.2 -40
-15
10 35 AMBIENT TEMPERATURE (C)
60
85
Figure 5. Output Efficiency vs. Load Current
Figure 8. Current Limit vs. Ambient Temperature, VOUT = 10 V
100 VOUT = 7.5V FSW = 700kHz L = 10H VIN = 5.5V
1.4
OSCILLATORY FREQUENCY (MHz)
90
VIN = 3.3V 80 VIN = 2.5V
1.2 1.0
RT = VIN
EFFICIENCY (%)
70
0.8
60 50 40 30 1 10 100 LOAD CURRENT (mA)
0.6
RT = GND
0.4 0.2 0 -40 VOUT = 10V VIN = 3.3V -15 10 35 AMBIENT TEMPERATURE (C) 60
04472-007
1000
85
Figure 6. Output Efficiency vs. Load Current
Figure 9. Oscillatory Frequency vs. Ambient Temperature
Rev. 0 | Page 6 of 16
04472-010
04472-008
40
ADP1610
4.4 0.50 FSW = 700kHz VFB = 1.3V RT = VIN 0.45 1.2 1.0 0.8
OSCILLATORY FREQUENCY (MHz)
QUIESCENT CURRENT (mA)
0.40
VIN = 5.5V
0.35 VIN = 3.3V 0.30 VIN = 2.5V 0.25
04472-014
0.6 0.4
RT = GND
VOUT = 10V 0 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0
04472-011
0.2
5.5
0.20 -40
-15
10 35 AMBIENT TEMPERATURE (C)
60
85
Figure 10. Oscillatory Frequency vs. Supply Voltage
Figure 13. Quiescent Current vs. Ambient Temperature
350
0.60 FSW = 1.23kHz VFB = 1.3V 0.55
300
VIN = 2.5V
250 VIN = 3.3V 200 VIN = 5.5V 150 100 50 0 -40
QUIESCENT CURRENT (mA)
SWITCH RESISTANCE (m)
0.50
VIN = 5.5V
0.45 VIN = 3.3V 0.40 VIN = 2.5V 0.35
04472-015
04472-012
-15
10 35 AMBIENT TEMPERATURE (C)
60
85
0.30 -40
-15
10 35 AMBIENT TEMPERATURE (C)
60
85
Figure 11. Switch Resistance vs. Ambient Temperature
Figure 14. Quiescent Current vs. Ambient Temperature
1.245
2.0 FSW = 1.23kHz VFB = 1V
1.24
1.8
FB REGULATION VOLTAGE (V)
SUPPLY CURRENT (mA)
1.235 1.23
1.6 VIN = 5.5V 1.4
1.225 1.22 1.215 1.21 -40
1.2 VIN = 3.3V 1.0 0.8 0.6 -40 VIN = 2.5V
04472-013
-25 -10
5 20 35 50 65 80 AMBIENT TEMPERATURE (C)
95
110
125
-15
10 35 AMBIENT TEMPERATURE (C)
60
85
Figure 12. FB Regulation Voltage vs. Ambient Temperature
Figure 15. Supply Current vs. Ambient Temperature
Rev. 0 | Page 7 of 16
04472-016
ADP1610
1.4 1.3 1.2 FSW = 700kHz VFB = 1V
CH1 = IL 200mA/DIV CH2 = VSW 5V/DIV
SUPPLY CURRENT (mA)
VIN = 3.3V VOUT = 10V ILOAD = 20mA FSW = 700kHz L = 10H
1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 -40 -15 10 35 AMBIENT TEMPERATURE (C) 60
VIN = 5.5V
2
VIN = 3.3V
VIN = 2.5V
04472-017
85
CH1 10.0mV CH2 5.00V
M400ns A CH2 T 136.000ns
10.0V
Figure 16. Supply Current vs. Ambient Temperature
Figure 19. Switching Waveform in Discontinuous Conduction
3.5 VIN = 3.3V SD = 0.4V 3.0
VIN = 3.3V, VOUT = 10V COUT = 10F, L = 10H, RC = 130 CC = 270pF, FSW = 700kHz CH1 = VOUT, 200mV/DIV CH2 = IOUT, 200mA/DIV
1
SUPPLY CURRENT (A)
2.5 2.0
1.5 1.0
2
0 -40
04472-018
15 70 TEMPERATURE (C)
125
CH1 200mV
CH2 10.0mV M200s
A CH2
7.60mV
Figure 17. Supply Current in Shutdown vs. Ambient Temperature
Figure 20. Load Transient Response, 700 kHz , VOUT = 10 V
CH1 = IL 500mA/DIV CH2 = VSW 5V/DIV
VIN = 3.3V VOUT = 10V ILOAD = 200mA FSW = 700kHz L = 10H
1
VIN = 3.3V, VOUT = 10V COUT = 10F, L = 4.7H, RC = 220k CC = 150pF, FSW = 1.2MHz CH1 = VOUT, 200mV/DIV CH2 = IOUT, 200mA/DIV
2
04472-019
CH1 10.0mV CH2 5.00V
M400ns A CH2 T 136.000ns
10.0V
CH1 200mV
CH2 10.0mV M200s
A CH2
7.60mV
Figure 18. Switching Waveform in Continuous Conduction
Figure 21. Load Transient Response, 1.2 MHz, VOUT = 10 V
Rev. 0 | Page 8 of 16
04472-022
1
2
04472-021
0.5
04472-020
1
ADP1610
2
2
4
4
3
CH1 = IL 1A/DIV CH2 = VIN CH3 = VOUT CH4 = SW, FSW = 700kHz
VIN = 3.3V VOUT = 10V IOUT = 0.2A CSS = 0nF
3
CH1 = IL 1A/DIV CH2 = VIN CH3 = VOUT CH4 = SW, FSW = 700kHz
VIN = 3.3V VOUT = 10V IOUT = 0.2A CSS = 0nF
04472-023
CH1 10.0mV CH2 2.00V CH3 10.0V CH4 10.00V
M100s T
A CH2
680mV
CH1 10.0mV CH2 2.00V CH3 10.0V CH4 10.00V
M100s T 405.600s
A CH2
1.72V
414.800s
Figure 22. Start-Up Response from VIN, SS = 0 nF
Figure 24. Start-Up Response from Shutdown, SS = 0 nF
2
2
4
4
3
CH1 = IL 1A/DIV CH2 = VIN CH3 = VOUT CH4 = SW, FSW = 700kHz
VIN = 3.3V VOUT = 10V IOUT = 0.2A CSS = 10nF
3
CH1 = IL 1A/DIV CH2 = SD CH3 = VOUT CH4 = SW, FSW = 700kHz
IOUT = 0.2A VIN = 3.3V VOUT = 10V CSS = 10nF
04472-024
1
CH1 10.0mV CH2 2.00V CH3 10.0V CH4 10.00V
M100s T
A CH2
680mV
CH1 10.0mV CH2 2.00V CH3 10.0V CH4 10.00V
M100s T 405.600s
A CH2
1.72V
414.800s
Figure 23. Start-Up Response from VIN, SS = 10 nF
Figure 25. Start-Up Response from Shutdown, SS = 10 nF
Rev. 0 | Page 9 of 16
04472-026
1
04472-025
1
1
ADP1610 THEORY OF OPERATION
The ADP1610 current-mode step-up switching converter converts a 2.5 V to 5.5 V input voltage up to an output voltage as high as 12 V. The 1.2 A internal switch allows a high output current, and the high 1.2 MHz switching frequency allows tiny external components. The switch current is monitored on a pulse-by-pulse basis to limit it to 2 A.
ON/OFF CONTROL
The SD input turns the ADP1610 regulator on or off. Drive SD low to turn off the regulator and reduce the input current to 10 nA. Drive SD high to turn on the regulator. When the dc-dc step-up switching converter is turned off, there is a dc path from the input to the output through the inductor and output rectifier. This causes the output voltage to remain slightly below the input voltage by the forward voltage of the rectifier, preventing the output voltage from dropping to zero when the regulator is shut down. Figure 28 shows the application circuit to disconnect the output voltage from the input voltage at shutdown.
CURRENT-MODE PWM OPERATION
The ADP1610 uses current-mode architecture to regulate the output voltage. The output voltage is monitored at FB through a resistive voltage divider. The voltage at FB is compared to the internal 1.23 V reference by the internal transconductance error amplifier to create an error current at COMP. A series resistorcapacitor at COMP converts the error current to a voltage. The switch current is internally measured and added to the stabilizing ramp, and the resulting sum is compared to the error voltage at COMP to control the PWM modulator. This currentmode regulation system allows fast transient response, while maintaining a stable output voltage. By selecting the proper resistor-capacitor network from COMP to GND, the regulator response is optimized for a wide range of input voltages, output voltages, and load conditions.
SETTING THE OUTPUT VOLTAGE
The ADP1610 features an adjustable output voltage range of VIN to 12 V. The output voltage is set by the resistive voltage divider (R1 and R2 in Figure 2) from the output voltage (VOUT) to the 1.230 V feedback input at FB. Use the following formula to determine the output voltage: VOUT = 1.23 x (1 + R1/R2) (1)
FREQUENCY SELECTION
The ADP1610's frequency is user-selectable to operate at either 700 kHz to optimize the regulator for high efficiency or to 1.2 MHz for small external components. Connect RT to IN for 1.2 MHz operation, or connect RT to GND for 700 kHz operation. To achieve the maximum duty cycle, which might be required for converting a low input voltage to a high output voltage, use the lower 700 kHz switching frequency.
Use an R2 resistance of 10 k or less to prevent output voltage errors due to the 10 nA FB input bias current. Choose R1 based on the following formula:
VOUT - 1.23 R1 = R2 x 1.23
(2)
INDUCTOR SELECTION
The inductor is an essential part of the step-up switching converter. It stores energy during the on-time, and transfers that energy to the output through the output rectifier during the offtime. Use inductance in the range of 1 H to 22 H. In general, lower inductance values have higher saturation current and lower series resistance for a given physical size. However, lower inductance results in higher peak current that can lead to reduced efficiency and greater input and/or output ripple and noise. Peak-to-peak inductor ripple current at close to 30% of the maximum dc input current typically yields an optimal compromise. For determining the inductor ripple current, the input (VIN) and output (VOUT) voltages determine the switch duty cycle (D) by the following equation: D=
SOFT START
To prevent input inrush current at startup, connect a capacitor from SS to GND to set the soft start period. When the ADP1610 is in shutdown (SD is at GND) or the input voltage is below the 2.4 V undervoltage lockout voltage, SS is internally shorted to GND to discharge the soft start capacitor. Once the ADP1610 is turned on, SS sources 3 A to the soft start capacitor at startup. As the soft start capacitor charges, it limits the voltage at COMP. Because of the current-mode regulator, the voltage at COMP is proportional to the switch peak current, and, therefore, the input current. By slowly charging the soft start capacitor, the input current ramps slowly to prevent it from overshooting excessively at startup.
VOUT - V IN VOUT
(3)
Rev. 0 | Page 10 of 16
ADP1610
Table 4. Inductor Manufacturers
Vendor Sumida 847-956-0666 www.sumida.com Part CMD4D11-2R2MC CMD4D11-4R7MC CDRH4D28-100 CDRH5D18-220 CR43-4R7 CR43-100 DS1608-472 DS1608-103 D52LC-4R7M D52LC-100M L (H) 2.2 4.7 10 22 4.7 10 4.7 10 4.7 10 Max DC Current 0.95 0.75 1.00 0.80 1.15 1.04 1.40 1.00 1.14 0.76 Max DCR (m) 116 216 128 290 109 182 60 75 87 150 Height (mm) 1.2 1.2 3.0 2.0 3.5 3.5 2.9 2.9 2.0 2.0
Coilcraft 847-639-6400 www.coilcraft.com Toko 847-297-0070 www.tokoam.com
Using the duty cycle and switching frequency, fSW, determine the on-time by the following equation: tON =
D f SW
(4)
The inductor ripple current (IL) in steady state is IL =
V IN x t ON L
The output capacitor maintains the output voltage and supplies current to the load while the ADP1610 switch is on. The value and characteristics of the output capacitor greatly affect the output voltage ripple and stability of the regulator. Use a low ESR output capacitor; ceramic dielectric capacitors are preferred. For very low ESR capacitors such as ceramic capacitors, the ripple current due to the capacitance is calculated as follows. Because the capacitor discharges during the on-time, tON, the charge removed from the capacitor, QC, is the load current multiplied by the on-time. Therefore, the output voltage ripple (VOUT) is
(5)
Solving for the inductance value, L, L=
V IN x t ON
I L
(6)
Make sure that the peak inductor current (the maximum input current plus half the inductor ripple current) is below the rated saturation current of the inductor. Likewise, make sure that the maximum rated rms current of the inductor is greater than the maximum dc input current to the regulator. For duty cycles greater than 50%, which occur with input voltages greater than one-half the output voltage, slope compensation is required to maintain stability of the currentmode regulator. For stable current-mode operation, ensure that the selected inductance is equal to or greater than LMIN:
VOUT =
where:
QC I xt = L ON C OUT C OUT
(8)
COUT is the output capacitance, IL is the average inductor current,
t ON = D f SW
(9)
and
L > L MIN =
VOUT - V IN 1.8 A x f SW
(7)
D=
VOUT - V IN VOUT
(10)
CHOOSING THE INPUT AND OUTPUT CAPACITORS
The ADP1610 requires input and output bypass capacitors to supply transient currents while maintaining constant input and output voltage. Use a low ESR (equivalent series resistance), 10 F or greater input capacitor to prevent noise at the ADP1610 input. Place the capacitor between IN and GND as close to the ADP1610 as possible. Ceramic capacitors are preferred because of their low ESR characteristics. Alternatively, use a high value, medium ESR capacitor in parallel with a 0.1 F low ESR capacitor as close to the ADP1610 as possible.
Choose the output capacitor based on the following equation:
C OUT
I L x (VOUT - V IN ) f SW x VOUT x VOUT
(11)
Table 5. Capacitor Manufacturers
Vendor AVX Murata Sanyo Taiyo-Yuden Phone No. 408-573-4150 714-852-2001 408-749-9714 408-573-4150 Web Address www.avxcorp.com www.murata.com www.sanyovideo.com www.t-yuden.com
Rev. 0 | Page 11 of 16
ADP1610
DIODE SELECTION
The output rectifier conducts the inductor current to the output capacitor and load while the switch is off. For high efficiency, minimize the forward voltage drop of the diode. For this reason, Schottky rectifiers are recommended. However, for high voltage, high temperature applications, where the Schottky rectifier reverse leakage current becomes significant and can degrade efficiency, use an ultrafast junction diode. Make sure that the diode is rated to handle the average output load current. Many diode manufacturers derate the current capability of the diode as a function of the duty cycle. Verify that the output diode is rated to handle the average output load current with the minimum duty cycle. The minimum duty cycle of the ADP1610 is The regulator loop gain is
AVL = V V FB x IN x G MEA x Z COMP x G CS x Z OUT (14) VOUT VOUT
where: AVL is the loop gain. VFB is the feedback regulation voltage, 1.230 V. VOUT is the regulated output voltage. VIN is the input voltage. GMEA is the error amplifier transconductance gain. ZCOMP is the impedance of the series RC network from COMP to GND. GCS is the current sense transconductance gain (the inductor current divided by the voltage at COMP), which is internally set by the ADP1610. ZOUT is the impedance of the load and output capacitor. To determine the crossover frequency, it is important to note that, at that frequency, the compensation impedance (ZCOMP) is dominated by the resistor, and the output impedance (ZOUT) is dominated by the impedance of the output capacitor. So, when solving for the crossover frequency, the equation (by definition of the crossover frequency) is simplified to
| AVL | = VFB VIN 1 x x GMEAx RCOMPx GCS x =1 VOUT VOUT 2 x fC x COUT
D MIN =
VOUT - V IN - MAX VOUT
(12)
where VIN-MAX is the maximum input voltage. Table 6. Schottky Diode Manufacturers
Vendor Motorola Diodes, Inc. Sanyo Phone No. 602-244-3576 805-446-4800 310-322-3331 Web Address www.mot.com www.diodes.com www.irf.com
LOOP COMPENSATION
The ADP1610 uses external components to compensate the regulator loop, allowing optimization of the loop dynamics for a given application. The step-up converter produces an undesirable right-half plane zero in the regulation feedback loop. This requires compensating the regulator such that the crossover frequency occurs well below the frequency of the right-half plane zero. The right-half plane zero is determined by the following equation:
(15)
where: fC is the crossover frequency. RCOMP is the compensation resistor. Solving for RCOMP,
R COMP =
V FZ (RHP) = IN V OUT
where:
R LOAD x 2 x L
2
2 x f C xC OUT x VOUT x VOUT V FB x V IN x G MEA x G CS
(16)
(13)
For VFB = 1.23, GMEA = 100 S, and GCS = 2 S,
RCOMP =
2.55 x 10 4 x f C x COUT x VOUT x VOUT VIN
(17)
FZ(RHP) is the right-half plane zero. RLOAD is the equivalent load resistance or the output voltage divided by the load current. To stabilize the regulator, make sure that the regulator crossover frequency is less than or equal to one-fifth of the right-half plane zero and less than or equal to one-fifteenth of the switching frequency.
Once the compensation resistor is known, set the zero formed by the compensation capacitor and resistor to one-fourth of the crossover frequency, or
C COMP = 2 x f C x RCOMP
(18)
where CCOMP is the compensation capacitor.
Rev. 0 | Page 12 of 16
ADP1610
Table 7. Recommended External Components for Popular Input/Output Voltage Conditions
VIN (V) 3.3 VOUT (V) 5 5 9 9 12 12 9 9 12 12 fSW (MHz) 0.700 1.23 0.700 1.23 0.700 1.23 0.700 1.23 0.700 1.23
ERROR AMP
REF
5
L (H) 4.7 2.7 10 4.7 10 4.7 10 4.7 10 4.7
COUT (F) 10 10 10 10 10 10 10 10 10 10
CIN (F) 10 10 10 10 10 10 10 10 10 10
R1 (k) 30.9 30.9 63.4 63.4 88.7 88.7 63.4 63.4 88.7 88.7
R2 (k) 10 10 10 10 10 10 10 10 10 10
RComp (k) 50 90.9 71.5 150 130 280 84.5 178 140 300
Ccomp (pF) 520 150 820 180 420 100 390 100 220 100
IOUT_MAX (mA) 600 600 350 350 250 250 450 450 350 350
gm
FB 2
COMP 1
Table 8. Typical Soft Start Period
RC CC
04472-004
C2
VIN (V) 3.3
Figure 26. Compensation Components
The capacitor, C2, is chosen to cancel the zero introduced by output capacitance ESR. Solving for C2,
5
C2 =
ESR x C OUT RCOMP
VOUT (V) 5 5 9 9 12 12 9 9 12 12
COUT (F) 10 10 10 10 10 10 10 10 10 10
CSS (nF) 20 100 20 100 20 100 20 100 20 100
tSS (ms) 0.3 2 2.5 8.2 3.5 15 0.4 1.5 0.62 2
(19)
For low ESR output capacitance such as with a ceramic capacitor, C2 is optional. For optimal transient performance, the RCOMP and CCOMP might need to be adjusted by observing the load transient response of the ADP1610. For most applications, the compensation resistor should be in the range of 30 k to 400 k, and the compensation capacitor should be in the range of 100 pF to 1.2 nF. Table 7 shows external component values for several applications.
Conversely, if fast startup is a requirement, the soft start capacitor can be reduced or even removed, allowing the ADP1610 to start quickly, but allowing greater peak switch current (see Figure 22 to Figure 25).
APPLICATION CIRCUITS
The circuit in Figure 27 shows the ADP1610 in a step-up configuration. The ADP1610 is used here to generate a 10 V regulator with the following specifications: VIN = 2.5 V to 5.5 V, VOUT = 10 V, and IOUT 400 mA.
4.7H L 3.3V
6
SOFT START CAPACITOR
The voltage at SS ramps up slowly by charging the soft start capacitor (CSS) with an internal 3 A current source. Table 8 listed the values for the soft start period, based on maximum output current and maximum switching frequency. The soft start capacitor limits the rate of voltage rise on the COMP pin, which in turn limits the peak switch current at startup. Table 8 shows a typical soft start period, tSS, at maximum output current, IOUT_MAX, for several conditions. A 20 nF soft start capacitor results in negligible input current overshoot at startup, and so is suitable for most applications. However, if an unusually large output capacitor is used, a longer soft start period is required to prevent input inrush current.
IN SD
ADP1610
SW 5 ON
3
D1
10V
R1 71.3k FB 2 R2 10k COMP 1 GND
4
CIN 10F
7
RT SS
8
CSS 22nF
Figure 27. 3.3 V to 10 V Step-Up Regulator
The output can be set to the desired voltage using Equation 2. Use Equation 16 and 17 to change the compensation network.
Rev. 0 | Page 13 of 16
04472-030
RCOMP 220k CCOMP 150pF
COUT 10F
ADP1610
DC-DC STEP-UP SWITCHING CONVERTER WITH TRUE SHUTDOWN
Some battery-powered applications require very low standby current. The ADP1610 typically consumes 10 nA from the input, which makes it suitable for these applications. However, the output is connected to the input through the inductor and the rectifying diode, allowing load current draw from the input while shut down. The circuit in Figure 28 enables the ADP1610 to achieve output load disconnect at shutdown. To shut down the ADP1610 and disconnect the output from the input, drive the SD pin below 0.4 V.
4.7H L 3.3V Q1 A FDC6331 R3 10k Q1 B
VGL -5V D9 BZT52C5VIS
R4 200
BAV99 C5 10nF C6 D8 10F D7
C4 10nF
R3 200 D5 D4 C3 10F
VGH 22V D5 BZT52C22
BAV99 D3 C2 1F
4.7H L 3.3V
6
C1 10nF D2 BAV99
ADP1610
IN SD FB 2 RT SS GND
4
D1 SW 5 R1 71.3k R2 10k
10V
ON
3
CIN 10F
D1 SW 5 R1 71.3k FB 2 R2 10k COMP 1 RCOMP 220k CCOMP 150pF COUT 10F 10V
7
ADP1610
6
8
COMP 1
IN SD RT SS GND
4
CSS 22nF
CIN 10F OFF CSS 22nF
7
Figure 29. TFT LCD Bias Supply
8
SEPIC POWER SUPPLY
The circuit in Figure 30 shows the ADP1610 in a single-ended primary inductance converter (SEPIC) topology. This topology is useful for an unregulated input voltage, such as a batterypowered application in which the input voltage can vary between 2.7 V to 5 V, and the regulated output voltage falls within the input voltage range. The input and the output are dc-isolated by a coupling capacitor, C1. In steady state, the average voltage of C1 is the input voltage. When the ADP1610 switch turns on and the diode turns off, the input voltage provides energy to L1, and C1 provides energy to L2. When the ADP1610 switch turns off and the diode turns on, the energy in L1 and L2 is released to charge the output capacitor, COUT, and the coupling capacitor, C1, and to supply current to the load.
4.7H L1 2.5V-5.5V
6
04472-031
Figure 28. Step-Up Regulator with True Shutdown
TFT LCD BIAS SUPPLY
Figure 29 shows a power supply circuit for TFT LCD module applications. This circuit has +10 V, -5 V, and +22 V outputs. The +10 V is generated in the step-up configuration. The -5 V and +22 V are generated by the charge-pump circuit. During the step-up operation, the SW node switches between 10 V and ground (neglecting forward drop of the diode and on resistance of the switch). When the SW node is high, C5 charges up to 10 V. C5 holds its charge and forward-biases D8 to charge C6 to -10 V. The Zener diode, D9, clamps and regulates the output to -5 V. The VGH output is generated in a similar manner by the
charge-pump capacitors, C1, C2, and C4. The output voltage is tripled and regulated down to 22 V by the Zener diode, D5.
ADP1610
IN SD RT SS GND
4
C1 10F SW 5 R1 16.8k
3.3V
ON
3
4.7H L2 FB 2 COMP 1 RCOMP 60k CCOMP 1nF
CIN 10F
7
8
COUT 10F R2 10k
04472-032
CSS 22nF
Figure 30. 3.3 V DC-DC Converter
Rev. 0 | Page 14 of 16
04472-033
3
RCOMP 220k CCOMP 150pF
COUT 10F
ADP1610 LAYOUT PROCEDURE
To get high efficiency, good regulation, and stability, a welldesigned printed circuit board layout is required. Where possible, use the sample application board layout as a model. Follow these guidelines when designing printed circuit boards (see Figure 1): * * * Keep the low ESR input capacitor, CIN, close to IN and GND. Keep the high current path from CIN through the inductor L1 to SW and PGND as short as possible. Keep the high current path from CIN through L1, the rectifier D1, and the output capacitor COUT as short as possible.
04472-028
* * * *
Keep high current traces as short and as wide as possible. Place the feedback resistors as close to the FB pin as possible to prevent noise pickup. Place the compensation components as close as possible to COMP. Avoid routing high impedance traces near any node connected to SW or near the inductor to prevent radiated noise injection.
Figure 32. Sample Application Board (Top Layer)
Figure 33. Sample Application Board (Silkscreen Layer)
Figure 31. Sample Application Board (Bottom Layer)
04472-027
Rev. 0 | Page 15 of 16
04472-029
ADP1610 OUTLINE DIMENSIONS
3.00 BSC
8 5
Preliminary Technical Data
3.00 BSC
1
4.90 BSC
4
PIN 1 0.65 BSC 1.10 MAX 8 0 0.80 0.60 0.40
0.15 0.00 0.38 0.22 COPLANARITY 0.10
0.23 0.08 SEATING PLANE
COMPLIANT TO JEDEC STANDARDS MO-187AA
Figure 34. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters
ORDERING GUIDE
Model ADP1610ARMZ-R71 Temperature Range -40C to +85C Package Description 8-Lead Mini Small Outline Package [MSOP] Package Option RM-8 Branding P03
1
Z = Pb-free part.
(c) 2004 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04472-0-10/04(0)
Rev. 0 | Page 16 of 16

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