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19-3283; Rev 3; 10/06
High-Performance, Single-Ended, Current-Mode PWM Controllers
General Description
The MAX5070/MAX5071 BiCMOS, high-performance, current-mode PWM controllers have all the features required for wide input voltage range isolated/nonisolated power supplies. These controllers are used for low- and high-power universal input voltage and telecom power supplies. The MAX5070/MAX5071 contain a fast comparator with only 60ns typical delay from current sense to the output for overcurrent protection. The MAX5070A/MAX5070B have an integrated error amplifier with the output at COMP. Soft-start is achieved by controlling the COMP voltage rise using external components. The frequency is adjustable from 20kHz to 1MHz with an external resistor and capacitor. The timing capacitor discharge current is trimmed allowing for programmable dead time and maximum duty cycle for a given frequency. The available saw-toothed waveform at RTCT can be used for slope compensation when needed. The MAX5071A/MAX5071B include a bidirectional synchronization circuit allowing for multiple controllers to run at the same frequency to avoid beat frequencies. Synchronization is accomplished by simply connecting the SYNC pins of all devices together. When synchronizing with other devices, the MAX5071A/MAX5071B with the highest frequency synchronizes the other devices. Alternatively, the MAX5071A/MAX5071B can be synchronized to an external clock with an opendrain output stage running at a higher frequency. The MAX5071C provides a clock output pulse (ADV_CLK) that leads the driver output (OUT) by 110ns. The advanced clock signal is used to drive the secondary-side synchronous rectifiers. The MAX5070/MAX5071 are available in 8-pin MAX(R) and SO packages and operate over the automotive temperature range of -40C to +125C.
Features
Pin-for-Pin Replacement for UC2842 (MAX5070A) and UC2844 (MAX5070B) 2A Drive Source and 1A Sink Capability Up to 1MHz Switching Frequency Operation Bidirectional Synchronization (MAX5071A/MAX5071B) Advanced Output Drive for Secondary-Side Synchronous Rectification (MAX5071C) Fast 60ns Cycle-by-Cycle Current Limit Trimmed Oscillator Capacitor Discharge Current Sets Maximum Duty Cycle Accurately Accurate 5% Start and Stop Voltage with 6V Hysteresis Low 32A Startup Current 5V Regulator Output (VREF) with 20mA Capability Overtemperature Shutdown
MAX5070/MAX5071
Ordering Information
PART MAX5070AASA MAX5070AAUA MAX5070BASA MAX5070BAUA TEMP RANGE -40C to +125C -40C to +125C -40C to +125C -40C to +125C PIN-PACKAGE 8 SO 8 MAX 8 SO 8 MAX
Specify lead-free by adding the + symbol at the end of the part number when ordering. Ordering Information continued at end of data sheet. Selector Guide appears at end of data sheet.
Pin Configurations
TOP VIEW
Applications
Universal Input AC/DC Power Supplies Isolated Telecom Power Supplies Isolated Power-Supply Modules Networking Systems Computer Systems/Servers Industrial Power Conversion Isolated Keep-Alive Circuits
COMP
1
8 7
VREF VCC OUT GND
FB 2 CS 3
MAX5070A MAX5070B
6 5
RT/CT 4
MAX/SO MAX is a registered trademark of Maxim Integrated Products, Inc. Pin Configurations continued at end of data sheet. 1
________________________________________________________________ Maxim Integrated Products
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.
High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
ABSOLUTE MAXIMUM RATINGS
VCC (Low-Impedance Source) to GND ..................-0.3V to +30V VCC (ICC < 30mA).....................................................Self Limiting OUT to GND ...............................................-0.3V to (VCC + 0.3V) OUT Current.............................................................1A for 10s FB, SYNC, COMP, CS, RT/CT, VREF to GND ...........-0.3V to +6V COMP Sink Current (MAX5070)..........................................10mA Continuous Power Dissipation (TA = +70C) 8-Pin MAX (derate 4.5mW/C above +70C) .............362mW 8-Pin SO (derate 5.9mW/C above +70C)...............470.6mW Operating Temperature Range (Automotive) ....-40C to +125C Maximum Junction Temperature .....................................+150C 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
(VCC = +15V, RT = 10k, CT = 3.3nF, VVREF = OPEN, CVREF = 0.1F, COMP = OPEN, VFB = 2V, CS = GND, TA = -40C to +85C, unless otherwise noted.) (Note 1)
PARAMETER REFERENCE Output Voltage Line Regulation Load Regulation Total Output Variation Reference Output-Noise Voltage Reference Output Short Circuit OSCILLATOR Initial Accuracy Voltage Stability Temp Stability RT/CT Voltage Ramp (P-P) RT/CT Voltage Ramp Valley Discharge Current Frequency Range FB Input Voltage FB Input Bias Current Open-Loop Voltage Gain Unity-Gain Bandwidth Power-Supply Rejection Ratio COMP Sink Current COMP Source Current COMP Output High Voltage COMP Output Low Voltage CURRENT-SENSE AMPLIFIER Gain Maximum Current-Sense Signal ACS VCS_MAX (Notes 3, 4) MAX5070A/B (Note 3) VCOMP = 5V, MAX5071_ 2.85 0.95 0.95 3 1 1 3.26 1.05 1.05 V/V V VRAMP VRAMP_VALLEY IDIS fOSC VFB IB(FB) AVOL fGBW PSRR ISINK ISOURCE VCOMPH VCOMPL 12V VCC 25V (Note 2) VFB = 2.7V, VCOMP = 1.1V VFB = 2.3V, VCOMP = 5V VFB = 2.3V, RCOMP = 15k to GND VFB = 2.7V, RCOMP = 15k to VREF 60 2 -0.5 5 2V VCOMP 4V FB shorted to COMP VRT/CT = 2V, TA = +25C 7.9 20 2.465 2.5 -0.01 100 1 80 6 -1.2 5.8 0.1 0.5 -1.8 TA = +25C 12V < VCC < 25V -40C < TA < +85C 51 54 0.2 0.5 1.7 1.1 8.3 8.7 1000 2.535 -0.1 57 0.5 kHz % % V V mA kHz V A dB MHz dB mA mA V V VVREF VLINE VLOAD VREFT VNOISE IS_SC TA = +25C, IVREF = 1mA 12V < VCC < 25V, IVREF = 1mA 1mA < IVREF < 20mA 1mA < IVREF < 20mA, 12V < VCC < 25V 10Hz < f < 10kHz, TA = +25C VVREF = 0V -30 4.9 50 -100 -180 4.950 5.000 0.4 6 5.050 4 25 5.1 V mV mV V V mA SYMBOL CONDITIONS MIN TYP MAX UNITS
ERROR AMPLIFIER (MAX5070A/MAX5070B)
2
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High-Performance, Single-Ended, Current-Mode PWM Controllers
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +15V, RT = 10k, CT = 3.3nF, VVREF = OPEN, CVREF = 0.1F, COMP = OPEN, VFB = 2V, CS = GND, TA = -40C to +85C, unless otherwise noted.) (Note 1)
PARAMETER Power-Supply Rejection Ratio Input Bias Current Delay From CS to OUT MOSFET DRIVER OUT Low-Side On-Resistance OUT High-Side On-Resistance ISOURCE (Peak) ISINK (Peak) Rise Time Fall Time UNDERVOLTAGE LOCKOUT/STARTUP Startup Voltage Threshold Minimum Operating Voltage After Turn-On Undervoltage-Lockout Hysteresis PWM Maximum Duty Cycle Minimum Duty Cycle SUPPLY CURRENT Startup Supply Current Operating Supply Current Zener Bias Voltage at VCC THERMAL SHUTDOWN Thermal Shutdown Thermal-Shutdown Hysteresis SYNC Frequency Range SYNC Clock Input High Threshold SYNC Clock Input Low Threshold SYNC Clock Input Minimum Pulse Width SYNC Clock Output High Level SYNC Clock Output Low Level SYNC Leakage Current TSHDN THYST fSYNC VSYNCINH VSYNCINL tPW_SYNCIN VSYNCOH VSYNCOL ISYNC 1mA external pulldown RSYNC = 5k VSYNC = 0V 200 4.0 4.7 0 0.01 0.1 0.1 20 3.5 0.8 +150 4 1000 C C kHz V V ns V V A ISTART ICC VZ VFB = VCS = 0V ICC = 25mA 24 32 3 26.5 65 5 A mA V DMAX DMIN MAX5070A/MAX5071A MAX5070B/MAX5071B/MAX5071C 94.5 48 96 49.8 97.5 50 0 % % VCC_START VCC_MIN UVLOHYST 15.2 9.2 16 10 6 16.8 10.8 V V V VRDS_ONL VRDS_ONH ISOURCE ISINK tr tf ISINK = 200mA ISOURCE = 100mA COUT = 10nF COUT = 10nF COUT = 1nF COUT = 1nF 4.5 3.5 2 1 15 22 10 7 A A ns ns SYMBOL PSRR ICS tCS_DELAY VCOMP = 0V 50mV overdrive CONDITIONS 12V VCC 25V MIN TYP 70 -1 60 -2.5 MAX UNITS dB A ns
MAX5070/MAX5071
SYNCHRONIZATION (MAX5071A/MAX5071B only) (Note 5)
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3
High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +15V, RT = 10k, CT = 3.3nF, VVREF = OPEN, CVREF = 0.1F, COMP = OPEN, VFB = 2V, CS = GND, TA = -40C to +85C, unless otherwise noted.) (Note 1)
PARAMETER ADV_CLK (MAX5071C only) ADV_CLK High Voltage ADV_CLK Low Voltage ADV_CLK Output Pulse Width ADV_CLK Rising Edge to OUT Rising Edge ADV_CLK Source and Sink Current VADV_CLKH VADV_CLKL tPULSE tADV_CLK IADV_CLK 10 IADV_CLK = 10mA source IADV_CLK = 10mA sink 85 110 2.4 3 0.4 V V ns ns mA SYMBOL CONDITIONS MIN TYP MAX UNITS
ELECTRICAL CHARACTERISTICS
(VCC = +15V, RT = 10k, CT = 3.3nF, VVREF = OPEN, CVREF = 0.1F, COMP = OPEN, VFB = 2V, CS = GND, TA = -40C to +125C, unless otherwise noted.) (Note 1)
PARAMETER REFERENCE Output Voltage Line Regulation Load Regulation Total Output Variation Reference Output Noise Voltage Reference Output Short Circuit OSCILLATOR Initial Accuracy Voltage Stability Temp Stability RT/CT Voltage Ramp (P-P) RT/CT Voltage Ramp Valley Discharge Current Frequency Range FB Input Voltage FB Input Bias Current Open-Loop Voltage Gain Unity-Gain Bandwidth Power-Supply Rejection Ratio COMP Sink Current COMP Source Current COMP Output High Voltage COMP Output Low Voltage VRAMP VRAMP_VALLEY IDIS fOSC VFB IB(FB) AVOL fGBW PSRR ISINK ISOURCE VCOMPH VCOMPL 12V VCC 25V (Note 2) VFB = 2.7V, VCOMP = 1.1V VFB = 2.3V, VCOMP = 5V VFB = 2.3V, RCOMP =15k to GND VFB = 2.7V, RCOMP = 15k to VREF 60 2 -0.5 5 2V VCOMP 4V FB shorted to COMP VRT/CT = 2V, TA = +25C 7.9 20 2.465 2.5 -0.01 100 1 80 6 -1.2 5.8 0.1 0.5 -1.8 TA = +25C 12V < VCC < 25V -40C < TA < +125C 51 54 0.2 1 1.7 1.1 8.3 8.7 1000 2.535 -0.1 57 0.5 kHz % % V V mA kHz V A dB MHz dB mA mA V V VVREF VLINE VLOAD VREFT VNOISE IS_SC TA = +25C, IVREF = 1mA 12V < VCC < 25V, IVREF = 1mA 1mA < IVREF < 20mA 1mA < IVREF < 20mA, 12V < VCC < 25V 10Hz < f < 10kHz, TA = +25C VVREF = 0V -30 4.9 50 -100 -180 4.950 5.000 0.4 6 5.050 4 25 5.1 V mV mV V V mA SYMBOL CONDITIONS MIN TYP MAX UNITS
ERROR AMPLIFIER (MAX5070A/MAX5070B)
4
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High-Performance, Single-Ended, Current-Mode PWM Controllers
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +15V, RT = 10k, CT = 3.3nF, VVREF = OPEN, CVREF = 0.1F, COMP = OPEN, VFB = 2V, CS = GND, TA = -40C to +125C, unless otherwise noted.) (Note 1)
PARAMETER CURRENT-SENSE AMPLIFIER Gain Maximum Current-Sense Signal Power-Supply Rejection Ratio Input Bias Current Delay From CS to OUT MOSFET DRIVER OUT Low-Side On-Resistance OUT High-Side On-Resistance ISOURCE (Peak) ISINK (Peak) Rise Time Fall Time UNDERVOLTAGE LOCKOUT/STARTUP Startup Voltage Threshold Minimum Operating Voltage After Turn-On Undervoltage-Lockout Hysteresis PWM Maximum Duty Cycle Minimum Duty Cycle SUPPLY CURRENT Startup Supply Current Operating Supply Current Zener Bias Voltage at VCC THERMAL SHUTDOWN Thermal Shutdown Thermal-Shutdown Hysteresis SYNC Frequency Range SYNC Clock Input High Threshold SYNC Clock Input Low Threshold SYNC Clock Input Minimum Pulse Width SYNC Clock Output High Level SYNC Clock Output Low Level TSHDN THYST fSYNC VSYNCINH VSYNCINL tPW_SYNCIN VSYNCOH VSYNCOL 1mA external pulldown RSYNC = 5k 200 4.0 4.7 0 0.1 20 3.5 0.8 +150 4 1000 C C kHz V V ns V V ISTART ICC VZ VFB = VCS = 0V ICC = 25mA 24 32 3 26.5 65 5 A mA V DMAX DMIN MAX5070A/MAX5071A MAX5070B/MAX5071B/MAX5071C 94.5 48 96 49.8 97.5 50 0 % % VCC_START VCC_MIN UVLOHYST 15.2 9.2 16 10 6 16.8 10.8 V V V VRDS_ONL VRDS_ONH ISOURCE ISINK tr tf ISINK = 200mA ISOURCE = 100mA COUT = 10nF COUT = 10nF COUT = 1nF COUT = 1nF 4.5 3.5 2 1 15 22 12 9 A A ns ns ACS VCS_MAX PSRR ICS tCS_DELAY 50mV overdrive (Notes 3, 4) MAX5070A/B (Note 3) VCOMP = 5V, MAX5071_ 12V VCC 25V 2.85 0.95 0.95 3 1 1 70 -1 60 -2.5 3.26 1.05 1.05 V/V V dB A ns SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX5070/MAX5071
SYNCHRONIZATION (MAX5071A/MAX5071B only, Note 5)
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5
High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +15V, RT = 10k, CT = 3.3nF, VVREF = OPEN, CVREF = 0.1F, COMP = OPEN, VFB = 2V, CS = GND, TA = -40C to +125C, unless otherwise noted.) (Note 1)
PARAMETER SYNC Leakage Current ADV_CLK (MAX5071C only) ADV_CLK High Voltage ADV_CLK Low Voltage ADV_CLK Output Pulse Width ADV_CLK Rising Edge to OUT Rising Edge ADV_CLK Source and Sink Current VADV_CLKH VADV_CLKL tPULSE tADV_CLK IADV_CLK 10 IADV_CLK = 10mA source IADV_CLK = 10mA sink 85 110 2.4 3 0.4 V V ns ns mA SYMBOL ISYNC VSYNC = 0V CONDITIONS MIN TYP 0.01 MAX 0.1 UNITS A
Note 1: Note 2: Note 3: Note 4: Note 5:
All devices are 100% tested at +25C. All limits over temperature are guaranteed by design, not production tested. Guaranteed by design, not production tested. Parameter measured at trip point of latch with VFB = 0V (MAX5070A/MAX5070B only). Gain is defined as A = VCOMP/VCS, 0 VCS 0.8V. Output Frequency equals oscillator frequency for MAX5070A/MAX5071A. Output frequency is one-half oscillator frequency for MAX5070B/MAX5071B/MAX5071C.
Typical Operating Characteristics
(VCC = 15V, TA = +25C, unless otherwise noted.)
OPERATING SUPPLY CURRENT (ICC) vs. TEMPERATURE AFTER STARTUP (fOSC = fSW = 250kHz)
MAX5070 toc02
BOOTSTRAP UVLO vs. TEMPERATURE
MAX5070 toc01
STARTUP CURRENT vs. TEMPERATURE
40 39 STARTUP CURRENT (A) 38 37 36 35 34 33 32 31 30 29 28 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) 6.0 5.5 SUPPLY CURRENT (mA) 5.0 4.5 4.0 3.5 3.0 2.5 2.0
CT = 100pF
15 14 13 12 11 10 9 8 7 6 5 TEMPERATURE (C) VCC (V)
VCC RISING
VCC FALLING
HYSTERESIS
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
6
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MAX5070 toc03
17 16
High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
Typical Operating Characteristics (continued)
(VCC = 15V, TA = +25C, unless otherwise noted.)
REFERENCE VOLTAGE (VREF) vs. TEMPERATURE
MAX5070 toc04
REFERENCE VOLTAGE (VREF) vs. REFERENCE LOAD CURRENT
MAX5070 toc05
REFERENCE VOLTAGE (VREF) vs. VCC VOLTAGE
IREF = 1mA
MAX5070 toc06 MAX5070 toc09
5.5 5.4 5.3 5.2 VVREF (V)
5.25 5.20 5.15 5.10 VVREF (V)
5.010
5.005 VVREF (V) 0
5.1 5.0 4.9 4.8 4.7 4.6 4.5
IREF = 1mA
5.05 5.00 4.95 4.90 4.85 4.80 4.75
5.000
IREF = 20mA
4.995
4.990 15 30 IREF (mA) 45 10 12 14 16 18 VCC (V) 20 22 24 26
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
OSCILLATOR FREQUENCY (fOSC) vs. TEMPERATURE
MAX5070 toc07
OSCILLATOR RT/CT DISCHARGE CURRENT vs. TEMPERATURE
8.55 8.50 8.45 8.40 8.35 8.30 8.25 8.20 8.15 8.10 8.05 8.00 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) DUTY CYCLE (%) VRT/CT = 2V
MAX5070 toc08
MAXIMUM DUTY CYCLE vs. TEMPERATURE
100 90 80 70 60 50 40 30 20 10 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) MAX5070B/MAX5071B/MAX5071C RT = 3.01k CT = 1nF MAX5070A/MAX5071A
550 540 OSCILLATOR FREQUENCY (kHz) 530 520 510 500 490 480 470 460 450 RT = 3.01k CT = 1nF
8.60 RT/CT DISCHARGE CURRENT (mA)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
MAX5070A/MAX5071A MAXIMUM DUTY CYCLE vs. FREQUENCY
MAX5070 toc10
CURRENT-SENSE (CS) TRIP THRESHOLD vs. TEMPERATURE
1.08 1.06 CS THRESHOLD (V) 1.04 1.02 1.00 0.98 0.96 0.94 0.92 0.90
MAX5070 toc11
100 90 80 DUTY CYCLE (%) 70 60 50 40 30 20 10 0 0 400 800 1200 CT = 1nF CT = 560pF
CT = 100pF
1.10
CT = 220pF
1600
2000
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
OSCILLATOR FREQUENCY (kHz)
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7
High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
Typical Operating Characteristics (continued)
(VCC = 15V, TA = +25C, unless otherwise noted.)
TIMING RESISTANCE (RT) vs. OSCILLATOR FREQUENCY
MAX5070 toc12
OUT IMPEDANCE vs. TEMPERATURE (RDS_ON PMOS DRIVER)
5.0 4.8 4.6 4.4 4.2 4.0 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 2.2 2.0
MAX5070 toc13
OUT IMPEDANCE vs. TEMPERATURE (RDS_ON NMOS DRIVER)
ISINK = 200mA
MAX5070 toc14 MAX5070 toc17
1000 CT = 1nF CT = 560pF CT = 220pF CT = 100pF
ISOURCE = 100mA
9.0 8.5 8.0 7.5 RDS_ON () 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0
RT RESISTANCE (k)
100
10
1
CT = 10nF CT = 4.7nF CT = 3.3nF CT = 2.2nF 10k 100k 1M 10M
0.1 FREQUENCY (Hz)
RDS_ON ()
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
PROPAGATION DELAY FROM CURRENT-LIMIT COMPARATOR TO OUT vs. TEMPERATURE
MAX5070 toc15
ERROR-AMPLIFIER OPEN-LOOP GAIN AND PHASE vs. FREQUENCY
MAX5070 toc16
COMP VOLTAGE LEVEL TO TURN OFF DEVICE vs. TEMPERATURE
2.5 10 -15 2.4 2.3 PHASE (DEGREES) 2.2 VCOMP (V) 2.1 2.0 1.9 1.8 1.7 1.6 1.5 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) 10V < VCC < 18V
100 90 PROPAGATION DELAY (ns) 80 70
140 120 100 GAIN (dB) 80 60 40 20 0 -20 PHASE GAIN
-40 -65 -90 -115 -140 -165 -190 10k 100k 1M 10M 100M
60 50 40 30 20 10 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
0.01 1
10 100 1k
FREQUENCY (Hz)
ADV_CLK RISING EDGE TO OUT RISING EDGE PROPAGATION DELAY vs. TEMPERATURE
114 112 110 108 106 104 102 100 98 96 94 92 90
MAX5070 toc18
ADV_CLK AND OUT WAVEFORMS
MAX5070 toc19
MAX5071C
VCC = 15V MAX5071C ADV_CLK 5V/div 10k LOAD
PROPAGATION DELAY (ns)
OUT 10V/div
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
20ns/div
8
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High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
Typical Operating Characteristics (continued)
(VCC = 15V, TA = +25C, unless otherwise noted.)
OUT SOURCE AND SINK CURRENTS
MAX5070 toc20
SUPPLY CURRENT (ICC) vs. OSCILLATOR FREQUENCY (CT = 100pF)
MAX5070 toc21
MAX5070A/MAX5071A MAXIMUM DUTY CYCLE vs. RT
90 80 DUTY CYCLE (%)
MAX5070 toc22
VCC = 15V COUT = 10nF VOUT 10V/div
10 9 SUPPLY CURRENT (mA) 8 7 6 5 4 TA = -40C 3 2 TA = +85C TA = +25C TA = +125C
100
70 60 50 40 30 20
CT = 1nF CT = 560pF CT = 220pF CT = 100pF
IOUT 2A/div
20Ons/div
20 120 220 320 420 520 620 720 820 920 1020 FREQUENCY (kHz)
100
1k RT ()
10k
100k
Pin Descriptions
MAX5070A/MAX5070B
PIN 1 2 3 4 5 6 7 8 NAME COMP FB CS RT/CT GND OUT VCC VREF Error-Amplifier Inverting Input Input to the PWM Comparator and Overcurrent Protection Comparator. The current-sense signal is compared to a signal proportional to the error-amplifier output voltage. Timing Resistor and Capacitor Connection. A resistor RT from RT/CT to VREF and capacitor CT from RT/CT to GND set the oscillator frequency. Power-Supply Ground. Place the VCC and VREF bypass capacitors close to the IC to minimize ground loops. MOSFET Driver Output. OUT connects to the gate of the external n-channel MOSFET. Power-Supply Input for MAX5070. Bypass VCC to GND with a 0.1F ceramic capacitor or a parallel combination of a 0.1F and a higher value ceramic capacitor. 5V Reference Output. Bypass VREF to GND with a 0.1F ceramic capacitor or a parallel combination of a 0.1F and a higher value ceramic capacitor. FUNCTION Error-Amplifier Output. COMP can be used for soft-start.
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9
High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
Pin Descriptions (continued)
MAX5071A/MAX5071B/MAX5071C
PIN MAX5071A/ MAX5071B 1 MAX5071C NAME FUNCTION COMP is level-shifted and connected to the inverting input of the PWM comparator. Pull up COMP to VREF through a resistor and connect an optocoupler from COMP to GND for proper operation. Bidirectional Synchronization Input. When synchronizing with other MAX5071A/MAX5071Bs, the higher frequency part synchronizes all other devices. ADV_CLK is an 85ns clock output pulse preceding the rising edge of OUT (see Figure 4). Use the pulse to drive the secondary-side synchronous rectifiers through a pulse transformer or an optocoupler (see Figure 8). Input to the PWM Comparator and Overcurrent Protection Comparator. The currentsense signal is compared to the voltage at COMP. Timing Resistor and Capacitor Connection. A resistor RT from RT/CT to VREF and capacitor CT from RT/CT to GND set the oscillator frequency. Power-Supply Ground. Place the VCC and VREF bypass capacitors close to the IC to minimize ground loops. MOSFET Driver Output. OUT connects to the gate of the external n-channel MOSFET. Power-Supply Input for MAX5071. Bypass VCC to GND with a 0.1F ceramic capacitor or a parallel combination of a 0.1F and a higher value ceramic capacitor. 5V Reference Output. Bypass VREF to GND with a 0.1F ceramic capacitor or a parallel combination of a 0.1F and a higher value ceramic capacitor.
1
COMP
2
--
SYNC
--
2
ADV_CLK
3 4 5 6 7 8
3 4 5 6 7 8
CS RT/CT GND OUT VCC VREF
10
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High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
VP
MAX5070A/MAX5070B
2.5V REFERENCE 2.5V 2.5V THERMAL SHUTDOWN PREREGULATOR 5V
UVLO
16V/10V
VOLTAGEDIVIDER
7 VCC 26.5V VDD 8 VREF
EN-REF
BG 5V REGULATOR SNS EN-DRV-BAR REG_OK DELAY VP VOLTAGEDIVIDER
1V ILIM S CLK R CS 3 CPWM GND 5 VEA FB 2 COMP 1 R 100% MAX DUTY CYCLE (MAX5070A) 50% MAX DUTY CYCLE (MAX5070B) 2R OSC Q 4 RT/CT Q 6 OUT
Figure 1. MAX5070A/MAX5070B Functional Diagram
Detailed Description
The MAX5070/MAX5071 current-mode PWM controllers are designed for use as the control and regulation core of flyback or forward topology switching power supplies. These devices incorporate an integrated low-side driver, adjustable oscillator, error amplifier (MAX5070A/ MAX5070B only), current-sense amplifier, 5V reference, and external synchronization capability (MAX5071A/ MAX5071B only). An internal +26.5V current-limited VCC clamp prevents overvoltage during startup. Five different versions of the MAX5070/MAX5071 are available. The MAX5070A/MAX5070B are the standard
versions with a feedback input (FB) and internal error amplifier. The MAX5071A/MAX5071B include bidirectional synchronization (SYNC). This enables multiple MAX5071A/MAX5071Bs to be connected and synchronized to the device with the highest frequency. The MAX5071C includes an ADV_CLK output, which precedes the MAX5071C's drive output (OUT) by 110ns. Figures 1, 2, and 3 show the internal functional diagrams of the MAX5070A/MAX5070B, MAX5071A/MAX5071B, and MAX5071C, respectively. The MAX5070A/ MAX5071A are capable of 100% maximum duty cycle. The MAX5070B/MAX5071B/MAX5071C are designed to limit the maximum duty cycle to 50%.
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11
High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
VP
MAX5071A/MAX5071B
2.5V 1V REFERENCE 2.5V 2.5V THERMAL SHUTDOWN PREREGULATOR 5V
UVLO
16V/10V
VOLTAGEDIVIDER
7 VCC 26.5V VDD 8 VREF
EN-REF
BG 5V REGULATOR SNS EN-DRV-BAR REG_OK DELAY VP VOLTAGEDIVIDER
1V ILIM S CLK R CS 3 GND 5 2R COMP 1 R CPWM OSC Q 100% MAX DUTY CYCLE (MAX5071A) 50% MAX DUTY CYCLE (MAX5071B) Q 6 OUT
4 RT/CT
SYNC 2
BIDIRECTIONAL SYNC
Figure 2. MAX5071A/MAX5071B Functional Diagram
Current-Mode Control Loop
The advantages of current-mode control over voltagemode control are twofold. First, there is the feed-forward characteristic brought on by the controller's ability to adjust for variations in the input voltage on a cycle-bycycle basis. Secondly, the stability requirements of the current-mode controller are reduced to that of a singlepole system unlike the double pole in the voltage-mode control scheme.
The MAX5070/MAX5071 use a current-mode control loop where the output of the error amplifier is compared to the current-sense voltage (VCS). When the current-sense signal is lower than the noninverting input of the PWM comparator, the output of the CPWM comparator is low and the switch is turned on at each clock pulse. When the current-sense signal is higher than the inverting input of the CPWM, the output of the CPWM comparator is high and the switch is turned off.
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High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
VP
MAX5071C
2.5V 1V REFERENCE 2.5V 2.5V THERMAL SHUTDOWN PREREGULATOR 5V
UVLO
16V/10V
VOLTAGEDIVIDER
7 VCC 26.5V VDD 8 VREF
EN-REF
BG 5V REGULATOR SNS EN-DRV-BAR REG_OK DELAY VP VOLTAGEDIVIDER
1V ILIM S CLK R CS 3 GND 5 2R COMP 1 R 4 RT/CT CPWM OSC Q 50% MAX DUTY CYCLE Q 6 OUT
ADV_CLK 2
Figure 3. MAX5071C Functional Diagram
VCC and Startup
In normal operation, VCC is derived from a tertiary winding of the transformer. However, at startup there is no energy delivered through the transformer, thus a resistor must be connected from VCC to the input power source (see RST and CST in Figures 5 to 8). During startup, CST charges up through RST. The 5V reference generator, comparator, error amplifier, oscillator, and drive circuit remain off during UVLO to reduce startup current below 65A. When V CC reaches the undervoltage-lockout threshold of 16V, the output driver begins to switch and the tertiary winding will supply power to VCC. VCC has an internal 26.5V current-limited clamp at its input to protect the device from overvoltage during startup.
Size the startup resistor, RST, to supply both the maximum startup bias (ISTART) of the device (65A max) and the charging current for CST. The startup capacitor CST must charge to 16V within the desired time period t ST (for example, 500ms). The size of the startup capacitor depends on: 1) IC operating supply current at a programmed oscillator frequency (fOSC). 2) The time required for the bias voltage, derived from a bias winding, to go from 0 to 11V. 3) The MOSFET total gate charge. 4) The operating frequency of the converter (fSW).
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High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
To calculate the capacitance required, use the following formula: V - 13V ICC + IG - INMIN (t SS ) RST CST = VHYST where: IG = QG fSW ICC is the MAX5070/MAX5071s' maximum internal supply current after startup (see the Typical Operating Characteristics to find the IIN at a given fOSC). QG is the total gate charge for the MOSFET, fSW is the converter switching frequency, VHYST is the bootstrap UVLO hysteresis (6V), and tSS is the soft-start time, which is set by external circuitry. Size the resistor RST according to the desired startup time period, tST, for the calculated CST. Use the following equations to calculate the average charging current (ICST) and the startup resistor (RST). V x CST ICST = SUVR t ST
Undervoltage Lockout (UVLO)
The minimum turn-on supply voltage for the MAX5070/MAX5071 is 16V. Once VCC reaches 16V, the reference powers up. There is 6V of hysteresis from the minimum turn-on voltage to the UVLO threshold. Once VCC reaches 16V, the MAX5070/MAX5071 will operate with VCC down to 10V. Once VCC goes below 10V the device is in UVLO. When in UVLO, the quiescent supply current into VCC falls back to 37A (typ), and OUT and VREF are pulled low.
MOSFET Driver
OUT drives an external n-channel MOSFET and swings from GND to VCC. Ensure that VCC remains below the absolute maximum VGS rating of the external MOSFET. OUT is a push-pull output with the on-resistance of the PMOS typically 3.5 and the on-resistance of the NMOS typically 4.5. The driver can source 2A typically and sink 1A typically. This allows for the MAX5070/MAX5071 to quickly turn on and off high gate-charge MOSFETs. Bypass VCC with one or more 0.1F ceramic capacitors to GND, placed close to the MAX5070/MAX5071. The average current sourced to drive the external MOSFET depends on the total gate charge (QG) and operating frequency of the converter. The power dissipation in the MAX5070/MAX5071 is a function of the average output drive current (IDRIVE). Use the following equation to calculate the power dissipation in the device due to IDRIVE: IDRIVE = QG x fSW PD = (IDRIVE + ICC) x VCC where I CC is the operating supply current. See the Typical Operating Characteristics for the operating supply current at a given frequency.
VSUVR VINMIN - 2 RST ICST + ISTART Where VINMIN is the minimum input supply voltage for the application (36V for telecom), VSUVR is the bootstrap UVLO wake-up level (16V), and ISTART is the VIN supply current at startup (65A, max). Choose a higher value for RST than the one calculated above if longer startup times can be tolerated in order to minimize power loss in RST. The above startup method is applicable to circuits where the tertiary winding has the same phase as the output windings. Thus, the voltage on the tertiary winding at any given time is proportional to the output voltage and goes through the same soft-start period as the output voltage. The minimum discharge time of CST from 16V to 10V must be greater than the soft-start time (tSS).
Error Amplifier (MAX5070A/MAX5070B)
The MAX5070 includes an internal error amplifier. The inverting input is at FB and the noninverting input is internally connected to a 2.5V reference. The internal error amplifier is useful for nonisolated converter design (see Figure 6) and isolated design with primary-side regulation through a bias winding (see Figure 5). In the case of a nonisolated power supply, the output voltage will be: R1 VOUT = 1 + x 2.5V R2 where R1 and R2 are from Figure 6.
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High-Performance, Single-Ended, Current-Mode PWM Controllers
MAX5071A/MAX5071B/MAX5071C Feedback
The MAX5071A/MAX5071B/MAX5071C are designed to be used with either an external error amplifier when designed into a nonisolated converter or an error amplifier and optocoupler when designed into an isolated power supply. The COMP input is level-shifted and connected to the inverting terminal of the PWM comparator (CPWM). Connect the COMP pin to the output of the external error amplifier for nonisolated design. Pull COMP high externally to at least 5V (or VREF) and connect the optocoupler transistor as shown in Figures 7 and 8. COMP can be used for soft-start and also as a shutdown. See the Typical Operating Characteristics to find the turn-off COMP voltage at different temperatures. If the maximum external COMP voltage is below 4.9V, it may reduce the PWM current-limit threshold below 1V. Use the following equation to calculate minimum COMP voltage (VCOMP) required for a guaranteed peak primary current (IP-P): VCOMP = (3 x IP-P x RCS) + 1.95V where RCS is a current-sense resistor.
Reference Output
VREF is a 5V reference output that can source 20mA. Bypass VREF to GND with a 0.1F capacitor.
MAX5070/MAX5071
Current Limit
The MAX5070/MAX5071 include a fast current-limit comparator to terminate the ON cycle during an overload or a fault condition. The current-sense resistor (RCS), connected between the source of the MOSFET and GND, sets the current limit. The CS input has a voltage trip level (VCS) of 1V. Use the following equation to calculate RCS: V RCS = CS IP - P IP-P is the peak current in the primary that flows through the MOSFET. When the voltage produced by this current (through the current-sense resistor) exceeds the currentlimit comparator threshold, the MOSFET driver (OUT) will turn the switch off within 60ns. In most cases, a small RC filter is required to filter out the leading-edge spike on the sense waveform. Set the time constant of the RC filter at 50ns. Use a current transformer to limit the losses in the current-sense resistor and achieve higher efficiency especially at low input-voltage operation.
Oscillator
The oscillator frequency is adjusted by adding an external capacitor and resistor at RT/CT (see RT and CT in the Typical Application Circuits). RT is connected from RT/CT to the 5V reference (VREF) and CT is connected from RT/CT to GND. VREF charges CT through RT until its voltage reaches 2.8V. CT then discharges through an 8.3mA internal current sink until CT's voltage reaches 1.1V, at which time C T is allowed to charge through RT again. The oscillator's period will be the sum of the charge and discharge times of CT. Calculate the charge time as: tC = 0.57 x RT x CT The discharge time is then: tD = RT x CT x 103 4.88 x RT - 1.8 x 103
Synchronization (MAX5071A/MAX5071B)
SYNC SYNC is a bidirectional input/output that outputs a synchronizing pulse and accepts a synchronizing pulse from other MAX5071A/MAX5071Bs (see Figures 7 and 9). As an output, SYNC is an open-drain p-channel MOSFET driven from the internal oscillator and requires an external pulldown resistor (RSYNC) from between 500 and 5k. As an input, SYNC accepts the output pulses from other MAX5071A/MAX5071Bs. Synchronize multiple MAX5071A/MAX5071Bs by connecting their SYNC pins together. All devices connected together will synchronize to the one operating at the highest frequency. The rising edge of SYNC will precede the rising edge of OUT by approximately the discharge time (tD) of the oscillator (see the Oscillator section). The pulse width of the SYNC output is equal to the time required to discharge the stray capacitance at SYNC through RSYNC plus the CT discharge time tD. Adjust RT/CT such that the minimum discharge time tD is 200ns.
The oscillator frequency will then be: fOSC = 1 tC + tD
For the MAX5070A/MAX5071A, the converter output switching frequency (fSW) is the same as the oscillator frequency (f OSC ). For the MAX5070B/MAX5071B/ MAX5071C, the output switching frequency is 1/2 the oscillator frequency.
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15
High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
Advance Clock Output (ADV_CLK) (MAX5071C) ADV_CLK is an advanced pulse output provided to facilitate the easy implementation of secondary-side synchronous rectification using the MAX5071C. The ADV_CLK pulse width is 85ns (typically) with its rising edge leading the rising edge of OUT by 110ns. Use this leading pulse to turn off the secondary-side synchronous-rectifier MOSFET (QS) before the voltage appears on the secondary (see Figure 8). Turning off the secondary-side synchronous MOSFET earlier avoids the shorting of the secondary in the forward converter. The ADV_CLK pulse can be propagated to the secondary side using a pulse transformer or highspeed optocoupler. The 85ns pulse, with 3V drive voltage (10mA source), significantly reduces the volt-second requirement of the pulse transformer and the advanced pulse alleviates the need for a highspeed optocoupler.
RT/CT
OUT
tADV_CLK = 110ns ADV_CLK
tPULSE = 85ns
Figure 4. ADV_CLK
Thermal Shutdown
When the MAX5070/MAX5071s' die temperature goes above +150C, the thermal-shutdown circuitry will shut down the 5V reference and pull OUT low.
Typical Application Circuits
VIN RST
CST 1 2 3 4 CT RCS COMP FB CS RT/CT VREF 8 7 6 5
VOUT
R1
MAX5070A VCC MAX5070B
OUT GND
R2
RT
N
Figure 5. MAX5070A/MAX5070B Typical Application Circuit (Isolated Flyback with Primary-Side Regulation)
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High-Performance, Single-Ended, Current-Mode PWM Controllers
Typical Application Circuits (continued)
VIN RST
MAX5070/MAX5071
CST 1 2 3 4 CT RCS COMP FB CS RT/CT VREF 8 7 6 5 N
VOUT
R1
MAX5070A VCC MAX5070B
OUT GND
R2
RT
Figure 6. MAX5070A/MAX5070B Typical Application Circuit (Non-Isolated Flyback)
VIN RST SYNC INPUT/OUTPUT CST RSYNC 1 2 3 4 CT RCS COMP SYNC MAX5071A VREF VCC OUT GND 8 7 6 5 N VOUT
MAX5071B
CS RT/CT
RT
Figure 7. MAX5071A/MAX5071B Typical Application Circuit (Isolated Flyback) ______________________________________________________________________________________ 17
High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
Typical Application Circuits (continued)
VD
VIN RST N QS N
VOUT
CST
QR VCC VREF RT RT/CT CT RCS COMP GND ADV_CLK OUT N
VD
MAX5071C
CS
MAX5078
0.5V/s PULSE TRANSFORMER
Figure 8. MAX5071C Typical Application Circuit (Isolated Forward with Secondary-Side Synchronous Rectification)
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High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
VIN VIN VIN
VCC VREF RT RT/CT CT OUT N RT CS CT RT/CT VREF
VCC OUT N RT CS CT RT/CT VREF
VCC OUT N
MAX5071A MAX5071B
MAX5071A MAX5071B
MAX5071A MAX5071B
CS
SYNC GND
SYNC GND
SYNC GND
TO OTHER MAX5071A/Bs RSYNC
Figure 9. Synchronization of MAX5071s
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19
High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
Selector Guide
PART MAX5070AASA MAX5070AAUA MAX5070BASA MAX5070BAUA MAX5071AASA MAX5071AAUA MAX5071BASA MAX5071BAUA MAX5071CASA MAX5071CAUA FEEDBACK/ ADVANCED CLOCK Feedback Feedback Feedback Feedback Sync. Sync. Sync. Sync. ADV_CLK ADV_CLK MAXIMUM DUTY CYCLE (%) 100 100 50 50 100 100 50 50 50 50 PIN-PACKAGE 8 SO 8 MAX 8 SO 8 MAX 8 SO 8 MAX 8 SO 8 MAX 8 SO 8 MAX PIN COMPATIBLE UC2842/UCC2842 UC2842/UCC2842 UC2844/UCC2844 UC2844/UCC2844 -- -- -- -- -- --
Pin Configurations (continued)
TOP VIEW
COMP SYNC CS
1 2 3
8 7
VREF VCC OUT GND
COMP 1 ADV_CLK 2
8 7
VREF VCC OUT GND
MAX5071A MAX5071B
MAX5071C
CS 3 6 5 RT/CT 4
6 5
RT/CT 4
MAX/SO
MAX/SO
Ordering Information (continued)
PART MAX5071AASA MAX5071AAUA MAX5071BASA MAX5071BAUA MAX5071CASA MAX5071CAUA TEMP RANGE -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C PIN-PACKAGE 8 SO 8 MAX 8 SO 8 MAX 8 SO 8 MAX
Chip Information
TRANSISTOR COUNT: 1987 PROCESS: BiCMOS
Specify lead-free by adding the + symbol at the end of the part number when ordering.
20
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High-Performance, Single-Ended, Current-Mode PWM Controllers
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.)
MAX5070/MAX5071
INCHES DIM A A1 B C e E H L MAX MIN 0.069 0.053 0.010 0.004 0.014 0.019 0.007 0.010 0.050 BSC 0.150 0.157 0.228 0.244 0.016 0.050
MILLIMETERS MAX MIN 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 1.27 BSC 3.80 4.00 5.80 6.20 0.40 1.27
N
E
H
VARIATIONS:
1
INCHES
MILLIMETERS MIN 4.80 8.55 9.80 MAX 5.00 8.75 10.00 N MS012 8 AA 14 AB 16 AC
TOP VIEW
DIM D D D
MIN 0.189 0.337 0.386
MAX 0.197 0.344 0.394
D A e B A1 L C
0-8
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, .150" SOIC
APPROVAL DOCUMENT CONTROL NO. REV.
21-0041
B
1 1
______________________________________________________________________________________
SOICN .EPS
21
High-Performance, Single-Ended, Current-Mode PWM Controllers MAX5070/MAX5071
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.)
8
4X S
8
INCHES DIM A A1 A2 b c D e E H MIN 0.002 0.030 MAX 0.043 0.006 0.037
MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95
O0.500.1 0.60.1
E
H
1
0.60.1
1
D
L
S
BOTTOM VIEW
0.014 0.010 0.007 0.005 0.120 0.116 0.0256 BSC 0.120 0.116 0.198 0.188 0.026 0.016 6 0 0.0207 BSC
0.25 0.36 0.13 0.18 2.95 3.05 0.65 BSC 2.95 3.05 4.78 5.03 0.41 0.66 0 6 0.5250 BSC
TOP VIEW
A2
A1
A
e
c b L
SIDE VIEW
FRONT VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, 8L uMAX/uSOP
APPROVAL DOCUMENT CONTROL NO. REV.
21-0036
J
1 1
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.
22 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
8LUMAXD.EPS

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