19-0603; Rev 1; 6/07 KIT ATION EVALU E L B A AVAIL 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode The MAX5096/MAX5097 easy-to-use, Dual Mode™, DC-DC converters operate as LDO (low dropout) or switch-mode buck converters. At a high output load, the converters operate as high-efficiency pulse-widthmodulated (PWM) switch-mode converters and reduce the power dissipation. The devices switch to a low-quiescent-current (IQ) LDO mode of operation at light load. During the key-off condition, the system’s microcontroller drives the LDO/BUCK input on the fly and forces the MAX5096/MAX5097 into LDO Mode, thereby reducing the quiescent current significantly. In Buck Mode, the MAX5096/MAX5097 operate from a 5V to 40V input voltage range and deliver up to 600mA of load current with excellent load and line regulation. The fixed-switching frequency versions of 135kHz and 330kHz are available. The MAX5096/MAX5097 DC-DC internal oscillator can be synchronized to an external clock. External compensation and a current-mode control scheme make it easy to design with. In LDO Mode, the MAX5096/MAX5097 operate from a 4V to 40V input voltage. The LDO Mode operation is intended for a lower output load current of up to 100mA. The quiescent current at 100µA load in LDO Mode is only 41µA (typ). Features ♦ High-Efficiency Switcher Mode (Buck Mode) or Low-Quiescent-Current Linear Regulator (LDO Mode) Operation ♦ Wide Operating Input Voltage Range +5V to +40V Buck Mode +4V to +40V LDO Mode ♦ Fixed 3.3V or 5V and Adjustable (1.24V to 11V) Output Voltage Versions ♦ 6µA (typ) Shutdown Current ♦ Fixed 135kHz or 330kHz Switching Frequency ♦ External Frequency Synchronization ♦ Programmable Soft-Start ♦ Integrated Microprocessor Reset (RESET) Circuit with Programmable Timeout Period ♦ Thermal and Short-Circuit Protection ♦ -40°C to +125°C Automotive Temperature Range ♦ Thermally-Enhanced Package Dissipates 2.6W at TA = +70°C (16-Pin TQFN) 1.7W at TA = +70°C (20-Pin TSSOP) Ordering Information PART TEMP RANGE PIN-PACKAGE PKG CODE MAX5096AATE+* -40°C to +125°C 16 TQFN-EP** T1655-2 The MAX5096/MAX5097 feature an enable input that shuts down the device, reducing the current consumption to 6µA (typ). Additional features include a power-on reset output with a capacitor-adjustable timeout period, programmable soft-start, output tracking, output overload, short-circuit and thermal shutdown protections. MAX5096BATE+ T1655-2 The MAX5096/MAX5097 operate over the -40°C to +125°C automotive temperature range and are available in thermally enhanced 20-pin TSSOP or 16-pin TQFN packages. -40°C to +125°C 16 TQFN-EP** MAX5096AAUP+* -40°C to +125°C 20 TSSOP-EP** MAX5096BAUP+* -40°C to +125°C 20 TSSOP-EP** U20E-4 MAX5097AATE+ -40°C to +125°C 16 TQFN-EP** T1655-2 MAX5097BATE+* -40°C to +125°C 16 TQFN-EP** T1655-2 MAX5097AAUP+* -40°C to +125°C 20 TSSOP-EP** U20E-4 MAX5097BAUP+* -40°C to +125°C 20 TSSOP-EP** U20E-4 *Future product—contact factory for availability. +Denotes lead-free package. **EP = Exposed pad. Applications + PGND LX Industrial LX TOP VIEW IN Pin Configurations IN Automotive 16 15 14 13 TOP VIEW + 12 EN 1 IN 1 20 LX IN 2 19 LX 18 N.C. IN 3 SGND 2 RESET 3 11 OUT MAX5096 MAX5097 10 ADJ 4 9 7 CT 6 TQFN 8 COMP SYNC 5 SS BP Dual Mode is a trademark of Maxim Integrated Products, Inc. U20E-4 LDO/BUCK PGND 4 SGND 5 MAX5096 MAX5097 17 EN 16 OUT RESET 6 15 ADJ BP 7 14 N.C. 13 LDO/BUCK N.C. 8 SYNC 9 12 COMP SS 10 11 CT TSSOP ________________________________________________________________ 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. 1 MAX5096/MAX5097 General Description MAX5096/MAX5097 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode ABSOLUTE MAXIMUM RATINGS (All voltages referenced to PGND, unless otherwise noted.) IN (transient, 1ms) ..................................................-0.3V to +45V SGND ....................................................................-0.3V to +0.3V LX....................................................................-1V to (VIN + 0.3V) LX Current ................................................................................2A EN ................................................................-0.3V to (VIN + 0.3V) BP, SYNC, LDO/BUCK, RESET to SGND...............-0.3V to +12V BP, RESET Output Current..................................................25mA CT, SS, ADJ, COMP to SGND ....................-0.3V to (VBP + 0.3V) OUT ........................................................................-0.3V to +11V OUT Short-Circuit Duration ........................................Continuous Continuous Power Dissipation (TA = +70°C)* 16-Pin TQFN (derate 33.3mW/°C above +70°C) ........2666mW 20-Pin TSSOP (derate 21.7mW/°C above +70°C) ......1739mW Thermal Resistance: (θJA, 16-Pin TQFN)* ...................................................30.0°C/W (θJC, 16-Pin TQFN).......................................................1.7°C/W (θJA, 20-Pin TSSOP)* .................................................46.0°C/W (θJC, 20-Pin TSSOP)........................................................2°C/W Operating Temperature Range .........................-40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-60°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C *As per JEDEC 51 Standard—Multilayer Board. 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 (VIN = +14V, IOUT = 1mA, CIN = 100µF, COUT = 22µF, L = 22µH, CBP = 1µF, VEN = +2.4V (Figure 2), SGND = PGND = 0V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = TJ = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS SYSTEM INPUT Input Voltage Range (LDO Mode) VIN_LDO LDO/BUCK = high 4 40 V Input Voltage Range (Buck Mode) VIN_BUCK LDO/BUCK = low 5 40 V Internal Input Undervoltage Lockout VUVLO 3.9 V Internal Input Undervoltage Lockout Hysteresis BP (Internal Regulator) Output Voltage Shutdown Supply Current 2 3.5 VUVLO_HYS VBP falling VBP 3.65 0.2 4.20 IQ LDO/BUCK = high, measured at input supply TA = -40°C to +125°C return, VOUT = 5V, IOUT = 100µA 38 70 IQ LDO/BUCK = high, measured at input supply TA = -40°C to return, VOUT = 5V, +125°C IOUT = 100mA 44 VIN = 14V, VOUT = 5V, IOUT = 0 680 IQ_BUCK ISHDN VIN = +4.5V, IBP = 100µA VEN = 0V, measured from VIN 3.75 V 4 Quiescent Supply Current (LDO Mode) Buck Converter No-Load Supply Current VBP rising V µA 100 µA TA = -40°C to +125°C 6 19 TA = -40°C to +85°C 6 12 µA _______________________________________________________________________________________ 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode (VIN = +14V, IOUT = 1mA, CIN = 100µF, COUT = 22µF, L = 22µH, CBP = 1µF, VEN = +2.4V (Figure 2), SGND = PGND = 0V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = TJ = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS BUCK MODE Supply Current (Buck Converter On) IS LDO/BUCK = low, VADJ = 1.4V, MAX5096, no switching 135kHz version 693 980 µA Supply Current (Buck Converter On) IS LDO/BUCK = low, VADJ = 1.4V, MAX5097, no switching 330kHz Version 720 1000 µA Fixed Output Voltage VOUT ADJ Set Point ADJ Input Bias Current 5V version, 5.5V ≤ VIN ≤ 40V, no load 4.85 5 5.12 3.3V version, 5.5V ≤ VIN ≤ 40V, no load 3.196 3.3 3.391 VFB 50% duty cycle, no load 1.21 1.235 1.27 V IFB VADJ = 1.5V 5 100 nA VADJTH_R ADJ rising 125 VADJTH_F ADJ falling 62 Maximum Duty Cycle DMAX VADJ = 0.5V Error Amplifier Transconductance GmEA VCOMP = VADJ, ICOMP = ±10µA Adjustable Output Voltage Range VADJ Dual Mode ADJ Threshold Minimum Output Current IOUT VIN = 6.5V to 40V ISW_LIM VIN = 6V to 40V Internal Switch On-Resistance RDS(ON) Switch Leakage Current Efficiency ISW_L η Switching Frequency fSW 136 1.235 Switch Current Limit mV 100 55 % 210 µS 11.000 V 600 1.15 mA 1.5 1.90 A VIN = 14V, IDRAIN = 100mA 0.9 2.1 Ω VEN = 0V 0.05 3 µA VIN = 14V, VOUT = 5V, IOUT = 400mA 85 VIN = 14V, VOUT = 3.3V, IOUT = 400mA 81 % MAX5096 120 135 148 kHz MAX5097 300 330 350 kHz MAX5096 120 500 kHz 500 kHz Synchronization SYNC Input fSYNC MAX5097 300 SYNC Input High Threshold VSYNCH VBP = 4V 2.0 SYNC Input Low Threshold VSYNCL VBP = 4V V 0.8 SYNC Input Minimum High Pulse Width 250 SYNC Input Leakage V VSYNC =11V V ns 1 µA LDO MODE Guaranteed Output Current IOUT (Note 2) 100 mA _______________________________________________________________________________________ 3 MAX5096/MAX5097 ELECTRICAL CHARACTERISTICS (continued) MAX5096/MAX5097 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode ELECTRICAL CHARACTERISTICS (continued) (VIN = +14V, IOUT = 1mA, CIN = 100µF, COUT = 22µF, L = 22µH, CBP = 1µF, VEN = +2.4V (Figure 2), SGND = PGND = 0V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = TJ = +25°C.) (Note 1) PARAMETER Output Voltage ADJ Set Point ADJ Input Bias Current SYMBOL VOUT VADJ IFB CONDITIONS 5V version, MAX5096B/MAX5097B, 5.5V ≤ VIN ≤ 40V, IOUT = 10mA 3.3V version, MAX5096A/MAX5097A, 4V ≤ VIN ≤ 40V, IOUT = 10mA IOUT = 10mA VADJ IOUT = 10mA Dropout Voltage ∆VDO IOUT = 100mA, VOUT = 0.98 x VOUT(NOMINAL) (5V version only), MAX5096B/MAX5097B Power-Supply Rejection Ratio Short-Circuit Current MAX UNITS 4.89 5 5.09 V 89 3.3 3.378 V 1.21 1.2375 1.26 V 0.5 100 nA 11.000 V 0.37 V 1.237 Rising edge of EN to VOUT = 10% VOUT(NOMINAL), RL = 500Ω, VADJ = SGND, LDO/BUCK = 4V, CSS = 2nF Startup Response Time Load Regulation TYP VADJ = 4V Adjustable Output Voltage Range Line Regulation MIN ∆VOUT / ∆VIN ∆VOUT / ∆IOUT PSRR ISC 300 5V version, +5.5V ≤ VIN ≤ +40V, IOUT = 100mA 0.125 3.3V version, +4V ≤ VIN ≤ +40V, IOUT = 100mA 0.093 µs mV/V 5V version, IOUT = 100µA to 100mA, VIN = +14V TJ = +25°C 0.242 0.374 TJ = -40°C to +125°C 0.242 1 3.3V version, IOUT = 100µA to 100mA, VIN = +14V TJ = +25°C 0.164 0.237 TJ = -40°C to +125°C 0.164 1 mV/mA IOUT = 10mA, f = 100Hz, 500mVP-P, VOUT = +5V, VIN = +14V VIN = 6V 60 150 330 dB 500 mA BUCK MODE (LDO MODE TRANSITION) LDO/BUCK High Threshold 2.0 V LDO/BUCK Low Threshold 0.8 V 1 µA LDO/BUCK Input Leakage LDO/BUCK = 11V Transition Timing from LDO Mode to Buck Mode Falling edge of LDO/BUCK to buck converter on 32 Clock Periods Transition Timing from Buck Mode to LDO Mode Rising edge of LDO/BUCK to LDO operation 100 µs SOFT-START, ENABLE (EN) AND RESET Soft-Start Charge Current ISS Soft-Start Reference Voltage VSS-REF EN High-Voltage Threshold VENH 4 VSS = 0.1V 3 5 7 µA VOUT = VOUT(NOMINAL) - 20% 0.9 0.99 1.1 V EN = high, regulator on 1.4 _______________________________________________________________________________________ V 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode (VIN = +14V, IOUT = 1mA, CIN = 100µF, COUT = 22µF, L = 22µH, CBP = 1µF, VEN = +2.4V (Figure 2), SGND = PGND = 0V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = TJ = +25°C.) (Note 1) PARAMETER EN Low-Voltage Threshold SYMBOL VENL EN Input Pulldown CONDITIONS MIN TYP Regulator off 0.4 VEN = 2V, LDO/BUCK = 4V 0.5 RESET Voltage Threshold High VRESET_H VOUT rising 89 92 RESET Voltage Threshold Low 87 90 VRESET_L VOUT falling RESET Output-Low Voltage VRL ISINK = 1mA RESET Output-High Leakage Current IRH VRESET = 5V, VADJ = 1.5V RESET Output Minimum Timeout Period CCT = 0 VOUT to RESET Delay Delay Comparator Threshold VCT rising Delay Comparator Threshold Hysteresis CT Charge Current % VOUT 92 % VOUT 0.2 V 1 µA µs µs 1.29 100 ICH CT Discharge Current 1.2374 IDISCH 0.74 1 V 94 6 1.18 UNITS µA 25 VOUT falling 10mV/µs, CCT = 0 VCT_TH MAX V mV 1.20 µA VCT = 1V 13.8 mA Temperature rising +165 °C 20 °C THERMAL SHUTDOWN Thermal Shutdown Temperature Thermal Shutdown Hysteresis TJ(SHDN) ∆TJ(SHDN) Note 1: Limits to -40°C are guaranteed by design. Note 2: The continuous maximum output current from LDO is limited by package power dissipation. _______________________________________________________________________________________ 5 MAX5096/MAX5097 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (VIN = +14V, VEN = +2.4V, MAX5097AATE+, Figures 2 and 4, TA = +25°C, unless otherwise specified.) 2.5 2.0 1.5 1.0 3.0 2.5 2.0 1.5 1.0 0.5 IOUT = 0 40 IOUT = 100µA 30 20 1 -40 -25 -10 5 20 35 50 65 80 95 110 125 100 10 INPUT VOLTAGE (V) INPUT VOLTAGE (V) TEMPERATURE (°C) NO-LOAD SUPPLY CURRENT vs. TEMPERATURE (BUCK MODE) SHUTDOWN CURRENT vs. TEMPERATURE OUTPUT VOLTAGE vs. TEMPERATURE (LDO MODE) 680 670 660 10 8 6 4 MAX5096 toc06 3.5 VOUT = 3.3V 3.4 OUTPUT VOLTAGE (V) 690 VEN = 0V VIN = 14V 12 SHUTDOWN CURRENT (µA) 700 14 MAX5096 toc05 VIN = 14V VOUT = 3.3V MAX5096 toc04 710 IOUT = 10mA IOUT = 100µA 3.3 IOUT = 10mA 3.2 3.1 650 2 640 -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) TEMPERATURE (°C) TEMPERATURE (°C) OUTPUT VOLTAGE vs. TEMPERATURE (BUCK MODE) DROPOUT VOLTAGE vs. OUTPUT CURRENT (LDO MODE) EFFICIENCY vs. LOAD CURRENT (VOUT = 3.3V) 3.34 IOUT = 100µA 3.30 IOUT = 100mA IOUT = 600mA 3.28 3.26 3.24 VOUT = 5V 0.16 0.14 0.12 0.10 0.08 0.06 TEMPERATURE (°C) fSW = 330kHz 90 80 70 60 50 0.04 20 0.02 10 VIN = 24V VIN = 5V 40 VIN = 40V VIN = 14V 30 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 100 EFFICIENCY (%) 3.36 DROPOUT VOLTAGE (V) VOUT = 3.3V MAX5096 toc09 0.18 MAX5096 toc07 3.38 3.32 3.0 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 MAX5096 toc08 NO-LOAD SUPPLY CURRENT (µA) 50 0 0 100 10 IOUT = 100mA 60 IOUT = 600mA 0 1 VIN = 14V VOUT = 3.3V 70 10 0.5 IOUT = 50mA 6 80 MAX5096 toc03 3.5 OUTPUT VOLTAGE (V) 3.0 QUIESCENT SUPPLY CURRENT vs. TEMPERATURE (LDO MODE) MAX5096 toc02 3.5 OUTPUT VOLTAGE (V) 4.0 MAX5096 toc01 4.0 OUTPUT VOLTAGE vs. INPUT VOLTAGE (BUCK MODE) QUIESCENT SUPPLY CURRENT (µA) OUTPUT VOLTAGE vs. INPUT VOLTAGE (LDO MODE) OUTPUT VOLTAGE (V) MAX5096/MAX5097 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode 0 0 20 40 60 OUTPUT CURRENT (mA) 80 100 0.01 0.1 LOAD CURRENT (A) _______________________________________________________________________________________ 1 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode EFFICIENCY vs. LOAD CURRENT (VOUT = 5V) MAX5096 toc10 90 EFFICIENCY (%) 80 VIN = 14V IOUT = 100µA to 50mA 70 50 VIN = 14V VIN = 5.5V MAX5096 toc12 MAX5096 toc11 100 60 LOAD-TRANSIENT RESPONSE (BUCK MODE) LOAD-TRANSIENT RESPONSE (LDO MODE) IOUT 50mA/div IOUT 200mA/div VOUT 50mV/div VOUT AC-COUPLED 100mV/div VIN = 24V 40 VIN = 40V 30 20 VIN = 14V ISTEP = 300mA to 600mA 10 0 0.01 0.1 1 1ms/div 2ms/div LOAD CURRENT (A) VIN STARTUP RESPONSE (LDO MODE) ENABLE STARTUP RESPONSE (LDO MODE) MAX5096 toc13 VIN = 14V IOUT = 0A CCT = 0.047µF VIN 10V/div MAX5096 toc15 VIN VIN = 14V IOUT = 100mA 10V/div CCT = 0.047µF VIN 10V/div VEN 5V/div VEN 5V/div VOUT 2V/div VOUT 2V/div VOUT 2V/div RESET 5V/div RESET 5V/div RESET 5V/div 10ms/div ENABLE STARTUP RESPONSE (BUCK MODE) 10ms/div SHUTDOWN RESPONSE THROUGH VIN (LDO MODE) MAX5096 toc16 VIN = 14V IOUT = 600mA CCT = 0.047µF VIN = 14V IOUT = 0A CCT = 0.047µF VEN 10V/div 10ms/div 10ms/div VIN STARTUP RESPONSE (BUCK MODE) MAX5096 toc14 SHUTDOWN RESPONSE THROUGH VIN (BUCK MODE) MAX5096 toc17 IOUT = 50mA VIN 10V/div MAX5096 toc18 IOUT = 50mA VIN 10V/div VIN 10V/div VEN 5V/div VEN 10V/div VEN 10V/div VOUT 2V/div VOUT 2V/div VOUT 2V/div RESET 5V/div RESET 5V/div RESET 5V/div 100ms/div 100ms/div _______________________________________________________________________________________ 7 MAX5096/MAX5097 Typical Operating Characteristics (continued) (VIN = +14V, VEN = +2.4V, MAX5097AATE+, Figures 2 and 4, TA = +25°C, unless otherwise specified.) MAX5096/MAX5097 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode Typical Operating Characteristics (continued) (VIN = +14V, VEN = +2.4V, MAX5097AATE+, Figures 2 and 4, TA = +25°C, unless otherwise specified.) LX VOLTAGE, SYNC INPUT, AND INDUCTOR CURRENT LX VOLTAGE AND INDUCTOR CURRENT LX VOLTAGE AND INDUCTOR CURRENT MAX5096 toc20 MAX5096 toc19 MAX5096 toc21 IOUT = 600mA IOUT = 0A VLX 10V/div VLX 10V/div VLX 5V/div SYNC INPUT 5V/div INDUCTOR CURRENT 500mA/div INDUCTOR CURRENT 200mA/div INDUCTOR CURRENT 500mA/div 1µs/div 2µs/div TRANSITION FROM BUCK MODE TO LDO MODE 1µs/div TRANSITION FROM LDO MODE TO BUCK MODE MAX5096 toc22 MAX5096 toc23 LDO/BUCK 5V/div LDO/BUCK 3V/div VOUT AC-COUPLED 200mV/div VOUT AC-COUPLED 200mV/div IOUT 100mA/div IOUT 100mA/div VIN = 14V IOUT = 100mA 400µs/div 8 VIN = 14V IOUT = 100mA 100µs/div _______________________________________________________________________________________ 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode PIN NAME FUNCTION TQFN TSSOP 1 4 PGND Power Ground. Return path for p-channel power MOSFET driver. Connect the input capacitor return, freewheeling diode anode, and output capacitor return terminals to PGND. 2 5 SGND Signal Ground. Connect SGND to PGND near the input bypass capacitor return terminal. Open-Drain, Active-Low Reset Output. RESET asserts low when OUT drops below the reset threshold. When output rises above 92% of the programmed level, RESET becomes high impedance after the reset timeout period. Connect a pullup resistor from RESET to the converter output to create a logic output. 3 6 RESET 4 7 BP 5 9 SYNC Synchronization Input. Connect SYNC to an external clock for synchronization. Connect SYNC to SGND when not used. 6 10 SS Soft-Start Timer Input. Connect an external capacitor from SS to SGND to adjust the softstart timeout period (see the Soft-Start (SS) section). 7 11 CT Reset Timeout Period. Connect a capacitor from CT to SGND to set the reset timeout period (see the Power-On Reset Output RESET section). 8 12 COMP 4V Internal Regulator Output. Bypass BP to SGND with a 1µF or greater ceramic capacitor. Buck Converter (Buck Mode) Control Loop Compensation. See the Compensation Network section for compensation network design. LDO mode does not need external compensation. LDO Mode/Buck Mode Select. Drive LDO/BUCK low to select the Buck Mode. The Buck Mode activates after 32 internal/external clock cycles. Force the LDO/BUCK high (> 2V), to select LDO Mode. The Buck Mode stops and LDO Mode is activated with a 100µs delay. 9 13 LDO/BUCK 10 15 ADJ Regulator Output Feedback Point. Connect ADJ to SGND for a fixed 3.3V (MAX5096A/MAX5097A) or 5V (MAX5096B/MAX5097B). For adjustable output voltage, use an external resistive divider to set VOUT. VADJ regulating set point is 1.237V. 11 16 OUT Converter Output. OUT must always be connected to the regulator output. Connect at least a 22µF low-ESR (equivalent series resistance) capacitor from OUT to PGND for stable operation. 12 17 EN Enable Input. EN is internally pulled to ground. Drive EN high to turn on the regulator. Force EN low or leave unconnected to place the device in shutdown mode. 13, 14 19, 20 LX Drain Connection of Internal p-Channel High-Side Switch 15, 16 1, 2, 3 IN Regulator Input. Bypass IN to PGND with a parallel combination of low-ESR ceramic and aluminum capacitor to handle the input ripple current. — 8, 14, 18 N. C. EP EP EP No Connection. Not internally connected. Exposed Pad. Connect externally to a large ground plane (SGND) for improved heat dissipation. Do not use EP as an electrical ground connection. _______________________________________________________________________________________ 9 MAX5096/MAX5097 Pin Description MAX5096/MAX5097 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode IN CIN VOUT INTERNAL 4V LDO CURRENT SENSE BP CBP OSCILLATOR AND RAMP GENERATOR - + DC CURRENT LIMITER VIN DC-DC ENABLE PWM PWM COMPARATOR + gm - CP LX + - SYNCRO SYNC LDO/BUCK MODE SELECTOR VOUT + COUT SS VREF R1 ADJ - FB OUT + SS VREF FEEDBACK SELECTOR LDO MODE AMPLIFIER CC L FB BUCK MODE GM AMPLIFIER COMP RC 0.9Ω GATE DRIVER MUX R2 0.12V LDO/ BUCK SELECTOR RPU EN RESET BIAS SOFTSTART INTERNAL BANDGAP UVLO THERMAL PROTECTION SS CSS RESET MAX5096 MAX5097 CT SGND PGND CCT Figure 1. Simplified Diagram 10 ______________________________________________________________________________________ 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode The MAX5096/MAX5097 are easy-to-use, high-efficiency, PWM current-mode, step-down switching converters in normal operation. The MAX5096/MAX5097 have an internal high-side p-channel 0.9Ω switch and use a low forward-drop freewheeling diode for rectification. In Buck Mode, the p-channel switches at the 135kHz or 330kHz frequency. Buck Mode uses a current-mode control architecture that offers excellent line-transient response, easier frequency compensation, and cycleby-cycle current limiting. The buck converter is compensated externally for a selected value/type of output inductor and capacitor. The internal p-channel switch acts as a pass element when operating in the low-quiescent-current LDO Mode. The LDO Mode can be selected on the fly through the LDO/BUCK input. During the key-off condition, the system’s microcontroller drives the LDO/BUCK input high and forces the MAX5096/MAX5097 into LDO Mode, reducing the quiescent current to 1µA (typ). When in LDO Mode, the device is capable of delivering up to 100mA, which may be limited by the device power dissipation. The LDO and switcher share the same pass element and the reference; however, the error amplifiers are different with their own compensation schemes. The MAX5096/MAX5097 include an integrated microprocessor reset circuit with an adjustable reset timeout period. The internal reset circuit monitors the regulator output voltage and asserts RESET low when the regulator output falls below the reset threshold voltage. Other features include an enable input, externally programmable soft-start, optimized current-limit protection in both LDO and Buck Modes, and thermal shutdown. Enable Input (EN) EN is a logic-level enable input that turns the device on or off. The logic-high and logic-low voltages for the EN input are 1.4V and 0.4V, respectively. Drive EN high to turn on the device, and drive it low to place the device in shutdown. Leaving EN unconnected disables the device since the EN is internally pulled low with a 0.5µA current, however, a forced pulldown of EN improves the noise immunity. The MAX5096/MAX5097 draw 6µA (typ) of supply current when in shutdown. EN withstands up to +40V, allowing EN to be connected directly to IN for always-on operation. The converter may be turned on and off while in both Buck and LDO Modes. Each time the EN is toggled, the output rises with a programmed soft-start period. Internal Regulator (BP)/ Undervoltage Lockout The MAX5096/MAX5097 include an internal 4V auxiliary regulator to power internal circuitry. Bypass the auxiliary regulator output (BP) to SGND with a 1µF ceramic capacitor physically located close to the device. The regulator is not intended to supply the external circuit other than pulling up the LDO/BUCK input or RESET. Do not load BP externally by more than 2mA. The regulator output is regulated to 4V with 7% accuracy during steady state. During turn-on, the BP voltage stabilizes after 250µs with a 1µF capacitor at BP. Drive EN high to turn on the internal regulator. The internal UVLO with hysteresis ensures stable operation, resulting in the monotonic rise of the output voltage. The UVLO circuit monitors the output of the regulator. The rising UVLO threshold is internally set to 3.65V (BP rising) with a 185mV hysteresis (BP falling). The 3.65V UVLO at the no-load BP output guarantees operation at VIN lower than 4V. Soft-Start (SS) Soft-start provides for the monotonic, glitch-free turn-on of the converter. Soft-start limits the input inrush current which may cause a glitch, especially if the source impedance is high. The soft-start period required also depends on the output capacitance and the closedloop bandwidth of converter. The soft-start period for the MAX5096/MAX5097 is externally programmable using a single capacitor (C SS ). The soft-start is achieved by the controlled ramping up of the error amplifier reference input. At startup, after VIN is applied and the UVLO threshold is reached, the device enters soft-start. During soft-start, 5µA is sourced into the capacitor (CSS) connected from SS to SGND (Figure 2) causing the reference voltage to ramp up slowly. When VSS reaches 1.237V, the output becomes fully active. Set the soft-start time (tSS) using following equation: V t SS = SS × CSS ISS where VSS is 1.237V, ISS is 5µA, tSS is in seconds, and CSS is in Farads. Pulling EN low quickly discharges the CSS capacitor, making it ready for the next soft-start period. ______________________________________________________________________________________ 11 MAX5096/MAX5097 Detailed Description MAX5096/MAX5097 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode VIN VIN BP 1.0µF CIN 100µF EN 22µH LDO/BUCK D1* B260/ MURS105 SYNC COMP MAX5096 MAX5097 RC 100kΩ CP 22pF VOUT LX COUT 22µF (CER.) + ADJ CC 1.2nF OUT 100kΩ SS CSS 0.047µF RESET RESET CT CCT 0.01µF GND PGND *USE MURS105 IN APPLICATIONS WHERE LDO MODE QUIESCENT CURRENT IS CRITICAL. Figure 2. Fixed Output Voltage Configuration Output Voltage Tracking/Sequencing The output voltages of multiple MAX5096/MAX5097 converters can be made to track by using the SS pin during turn-on and turn-off (see Figure 3). SS is pulled up using a 5µA current source and connecting SS of multiple MAX5096/MAX5097s, raising the references with the same slope. Tracking the converters reduces the differential voltages between the core and I/O voltages during turn-on, turn-off, and brownout. If any one converter output drops due to shutdown or an overload fault situation, the SS drops, pulling down all the converters simultaneously. The rate of fall of output voltages, however, depends on the output capacitance and load of the individual converter. Multiple voltage sequencing can be done by daisychaining several MAX5096/MAX5097s. The RESET of the first converter can be connected to EN of the second converter. This allows the first converter to come up first every time the system is powered up. Power-On Reset Output (RESET) A supervisor circuit is integrated in the MAX5096/ MAX5097. RESET is an open-drain output. RESET pulls low as soon as VOUT drops below 90% of its nominal regulation voltage. Once the output voltage rises above 92% of the set output voltage, the RESET output enters 12 a high-impedance state after the active timeout period (tRP). The active timeout period is externally programmable using a single capacitor from CT to ground. Use the following equation to calculate the required timeout period for the power-on reset: V tRP = CT −TH × CCT ICH where VCT-TH is 1.237V, ICH is 1µA, tRP is in seconds, and CCT is in Farads. To obtain a logic-voltage output, connect a pullup resistor from RESET to a logic-supply voltage. The internal open-drain MOSFET can sink 1mA while providing a TTL logic-low signal. If unused, ground RESET or leave it unconnected. The power-on reset behavior is the same in both the LDO and Buck Modes of operation. Oscillator/Synchronization Input (SYNC) The MAX5096/MAX5097 internal oscillator generates a factory-preset frequency of either 135kHz (MAX5096) or 330kHz (MAX5097). The 135kHz version keeps the maximum fundamental frequency below 150kHz, which keeps the third harmonic below 450kHz and under the ______________________________________________________________________________________ 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode Output Voltage Selection VOUT2 VOUT1 SOFT-START STOP RATIOMETRIC TRACKING OUTPUTS VOUT1 VOUT2 VOUT3 STOP SOFT-START The MAX5096/MAX5097 can be configured as either a preset fixed output voltage or an adjustable output voltage device. Connect ADJ to ground to select the factory-preset output voltage option (Figure 2). The MAX5096A/MAX5097A and MAX5096B/MAX5097B provide a fixed output voltage equal to 3.3V and 5V, respectively (see the Selector Guide). The MAX5096/ MAX5097 become an adjustable version as soon as the devices detect about 125mV at the ADJ pin. The resistor-divider at ADJ increases the ADJ voltage above 125mV and also adjusts the output voltage depending upon the resistor values. In adjustable mode, select an output between +1.273V and +11V using two external resistors connected as a voltage-divider to ADJ (Figure 4). Set the output voltage using the following equation: R1 ⎞ ⎛ VOUT = VADJ × ⎜1 + ⎟ ⎝ R2 ⎠ SEQUENCED OUTPUTS Figure 3. Output Voltage Tracking/Sequencing lower end of the AM band. The MAX5096 is suitable for noise-sensitive applications like AM radio power supply. For an application where size is more important, use the MAX5097, which runs at 330kHz frequency. The high-frequency operation reduces the size and cost of the external inductor and capacitor. The MAX5096/MAX5097 can be synchronized using an external signal. The MAX5096 can be synchronized from 120kHz to 500kHz, while the MAX5097 is capable of synchronizing from 300kHz to 500kHz. The external synchronization feature makes frequency hopping possible depending on the selected AM channel. Connect SYNC to ground, if not used. Thermal Protection When the junction temperature exceeds TJ = +165°C, an internal thermal sensor signals the shutdown logic, which turns off the regulator (both in Buck Mode and LDO Mode), and discharges the soft-start capacitor allowing the IC to cool. The thermal sensor turns the regulator on again after the IC’s junction temperature cools by 20°C, resulting in a cycled output during continuous thermal-overload conditions. The thermal hysteresis and a soft-start period limit the average power dissipation into the device during continuous fault condition. During operation, do not exceed the absolute maximum junction temperature rating of TJ = +150°C. where VADJ = 1.273V and R2 is chosen to be approximately 100kΩ. Connect ADJ to GND if adjustable mode is not used. Inductor Selection Three key inductor parameters must be specified for proper operation with the MAX5096/MAX5097: inductance value (L), peak inductor current (I PEAK), and inductor saturation current (I SAT ). The minimum required inductance is a function of operating frequency, input-to-output voltage differential, and the peak-topeak inductor current (∆IP-P). Higher ∆IP-P allows for a lower inductor value, while a lower ∆IP-P requires a higher inductor value. A lower inductor value minimizes size and cost and improves large-signal and transient response, but reduces efficiency due to higher peak currents and higher peak-to-peak output voltage ripple for the same output capacitor. On the other hand, higher inductance increases efficiency by reducing the ripple current. Resistive losses due to extra wire turns can exceed the benefit gained from lower ripple current levels, especially when the inductance is increased while keeping the dimension of the inductor constant. A good compromise is to choose ∆IP-P equal to 40% of the full load current. Calculate the inductor value using the following equation: (V − V ) V L = OUT IN OUT VIN × fSW × ∆IP−P ______________________________________________________________________________________ 13 MAX5096/MAX5097 Applications Information VOUT3 MAX5096/MAX5097 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode 5V TO 40V VIN VIN BP 1.0µF CIN 100µF EN 22µH LDO/BUCK VOUT LX D1* COUT B260/ MURS105 22µF SYNC COMP MAX5096 MAX5097 RC CP + R1 ADJ R2 CC OUT RPU SS RESET RESET CT GND CSS *USE MURS105 IN APPLICATIONS WHERE LDO MODE QUIESCENT CURRENT IS CRITICAL. PGND CCT Figure 4. Adjustable Output Voltage Configuration use typical values of VIN and fSW so that efficiency is optimum for typical conditions. The switching frequency (fSW) is fixed at 135kHz (MAX5096) and 330kHz (MAX5097). f SW can also be varied from 120kHz to 500kHz (MAX5096) and from 300kHz to 500kHz (MAX5097) when synchronized to an external clock (see the Oscillator/ Synchronization Input (SYNC) section). The peak-to-peak inductor current, which reflects the peak-to-peak output ripple, is worst at the maximum input voltage. See the Output Capacitor Selection section to verify that the worst-case output ripple is acceptable. The inductor saturating current (ISAT) is also important to avoid runaway current during continuous output short circuit. Select an inductor with an ISAT specification higher than the maximum peak current limit of 1.9A. The Buck Mode operation determines the inductor and output capacitor values. However, the values of the inductor, its DCR, and the output capacitance/ESR affect the closed-loop transfer function both in Buck and LDO Modes. The internal compensation of the MAX5096/MAX5097 in LDO Mode limits the values of these external components. Make sure that the combination of output inductor, capacitor, and ESR falls within the range specified in following Table 1. 14 Table 1. Inductor/Output Capacitor Selection INDUCTOR OUTPUT CAPACITOR (COUT) 22µF, ESR = 5mΩ to 20mΩ (ceramic) 22µH 47µF, ESR = 40mΩ to 150mΩ 100µF, ESR = 30mΩ to 100mΩ 470µF / ESR = 60Ω to 400mΩ 22µF, ESR = 5mΩ to 20mΩ (ceramic) 47µH 47µF / ESR = 40mΩ to 150mΩ 100µF / ESR = 30mΩ to 100mΩ 470µF / ESR = 60mΩ to 400mΩ 22µF, ESR = 5mΩ to 20mΩ (ceramic) 100µH 47µF / ESR = 40mΩ to 150mΩ 100µF / ESR = 30mΩ to 100mΩ 470µF / ESR = 60mΩ to 400mΩ Output Capacitor Selection The allowable output voltage ripple and the maximum deviation of the output voltage during load steps determine the output capacitance and its ESR. The output ______________________________________________________________________________________ 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode COUT = ∆IP−P 16 × ∆VQ × fSW ESR = ∆VESR ∆IP−P ∆IP-P is the peak-to-peak inductor current and fSW is the converter’s switching frequency. The allowable deviation of the output voltage during fast load transients also determines the output capacitance, its ESR, and its equivalent series inductance (ESL). The output capacitor supplies the load current during a load step until the controller responds with a greater duty cycle. The response time (tRESPONSE ) depends on the closed-loop bandwidth of the converter (see the Compensation Network section). The resistive drop across the output capacitor’s ESR, the drop across the capacitor’s ESL, and the capacitor discharge, causes a voltage drop during the load step. Use a combination of low-ESR tantalum/aluminum electrolytic and ceramic capacitors for better transient load and voltage ripple performance. Non-leaded capacitors and/or multiple parallel capacitors help reduce the ESL. Keep the maximum output voltage deviation below the tolerable limits of the electronics being powered. Use the following equations to calculate the required ESR, ESL, and capacitance value during a load step: ∆VESR ∆ISTEP ×t I COUT = STEP RESPONSE ∆VQ where ISTEP is the load step, tSTEP is the rise time of the load step, and tRESPONSE is the response time of the controller. The response time of the converter is approximately one third of the inverse of its closed-loop bandwidth and also depends on the phase margin. Rectifier Selection The MAX5096/MAX5097 require an external Schottky/ fast-recovery diode rectifier as a freewheeling diode. Connect this rectifier close to the device using short leads and short PC board traces. Choose a rectifier with a continuous current rating greater than the highest output current-limit threshold (1.9A) and with a voltage rating greater than the maximum expected input voltage, VIN. Use a low forward-voltage-drop Schottky rectifier to limit the negative voltage at LX. Avoid higher than necessary reverse-voltage Schottky rectifiers that have higher forward-voltage drops. Use a 60V (max) Schottky rectifier with a 2A current rating. The Schottky rectifier leakage current at high temperature significantly increases the quiescent current in LDO Mode. In applications where LDO Mode quiescent current is important, use an ultra-fast switching diode to limit the leakage current. In this type of application, use MURS105, MURS120 for their fast-switching and lowleakage features. Input Capacitor Selection The discontinuous input current of the buck converter causes large input ripple currents and therefore, the input capacitor must be carefully chosen to keep the input voltage ripple within design requirements. The input voltage ripple is comprised of ∆VQ (caused by the capacitor discharge) and ∆VESR (caused by the ESR of the input capacitor). The total voltage ripple is the sum of ∆VQ and ∆VESR. Calculate the input capacitance and ESR required for a specified ripple using the following equations (continuous mode): ESR = CIN = ∆VESR ∆IP−P ⎞ ⎛ ⎜ IOUT _ MAX + ⎟ ⎝ 2 ⎠ IOUT _ MAX × D(1− D) ESR = ESL = ∆VESL × t STEP ISTEP ∆VQ × fSW where ∆IP−P = (VIN − VOUT ) × VOUT and VIN × fSW × L V D = OUT VIN IOUT_MAX is the maximum output current and D is the duty cycle. ______________________________________________________________________________________ 15 MAX5096/MAX5097 ripple is mainly composed of ∆V Q (caused by the capacitor discharge) and ∆VESR (caused by the voltage drop across the ESR of the output capacitor). Normally, a good approximation of the output voltage ripple is ∆VRIPPLE ≈ ∆VESR + ∆VQ. If using ceramic capacitors, assume the contribution to the output voltage ripple from the ESR and the capacitor discharge to be equal to 20% and 80%, respectively. If using aluminum electrolyte capacitors, assume the contribution to the output voltage ripple from the ESR and the capacitor discharge to be equal to 90% and 10%, respectively. Use the following equations for calculating the output capacitance and its ESR for required peak-to-peak output voltage ripple. MAX5096/MAX5097 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode Compensation Network The MAX5096/MAX5097 in LDO Mode are compensated internally with a compensation network around the LDO error amplifier. When in Buck Mode, the DC-DC gM amplifier must be externally compensated using a network connected from COMP to ground. The currentmode control architecture reduces the compensation network to a single pole-zero. The RC and C network, connected from the internal transconductance amplifier output to SGND, can provide a single pole-zero pair. Choose all the power components like the inductor, output capacitor, and ESR first and design the compensation network around them. Choose the closedloop bandwidth (fC) to be approximately 1/10 of the switching frequency. See the following equations to calculate the compensation values for the low-ESR output capacitor with ESR zero frequency, approximately a decade higher than fC. Calculate the dominant pole due to the output capacitor (COUT) and the load (ROUT): 1 fPO = 2 × π × COUT × ROUT where ROUT = VOUT / ILOAD. Calculate the RC using following equation: RC = VO × fC gMC × ROUT × gm × VADJ × fPO where g MC is the control to output gain of the MAX5096/MAX5097 buck converter and is equal to 1.06. VADJ is the feedback set point equal to 1.237V and gm (transconductance amplifier gain) is equal to 136µS. See Figure 2. Place a zero (f Z) at 0.9 x f PO: CC = 1 2 × π × RCFPO × fPO Finally, place a high-frequency pole at the frequency equal to half of the converter switching frequency (fSW). CP = 1 π × RC × fSW Switching Between LDO Mode and Buck Mode The MAX5096/MAX5097 switch between the Buck Mode and LDO Mode on the fly. However, care must be taken to reduce output glitch or overshoot during the switching. Buck Mode to LDO Mode The LDO Mode is intended for the low 100mA output current while the buck converter delivers up to 600mA output current. It is important to first reduce the output load below 100mA before switching to the LDO Mode. If the output load is higher than 100mA, the MAX5096/MAX5097 may go into the current limit and the output will drop significantly. Whenever the mode is changed, output is expected to glitch because the loop dynamics change due to different error amplifiers when operating in the LDO and Buck Modes. The output voltage undershoot can be minimized by reducing the output load during switching and using larger output capacitance. LDO Mode to Buck Mode When switching from the LDO Mode to Buck Mode, a fixed amount of delay (32 cycles) is applied so that the buck converter control loop and oscillator reach their steady-state conditions. The 32-cycle delay translates to approximately 250µs and 100µs for 150kHz and 330kHz switching frequency versions, respectively. It is recommended that the output load of 600mA must be delayed by at least this much time to allow the MAX5096/MAX5097 to switch to high-current Buck Mode. This ensures that the output does not drop due to the LDO current-limit protection mechanism. PC Board Layout Guidelines 1) Proper PC board layout is essential. Minimize ground noise by connecting the anode of the freewheeling rectifier, the input bypass capacitor ground lead, and the output filter capacitor ground lead to a large PGND plane. 2) Minimize lead lengths to reduce stray capacitance, trace resistance, and radiated noise. In particular, place the Schottky/fast recovery rectifier diode right next to the device. Place the compensation network physically close to the MAX5096/MAX5097. 16 ______________________________________________________________________________________ 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode Chip Information PROCESS: BiCMOS Selector Guide PART OUTPUT VOLTAGE (V) SWITCHING FREQUENCY (kHz) MAX5096A_ _ _ +3.3/Adjustable 135 MAX5096B_ _ _ +5.0/Adjustable 135 MAX5097A_ _ _ +3.3/Adjustable 330 MAX5097B_ _ _ +5.0/Adjustable 330 ______________________________________________________________________________________ 17 MAX5096/MAX5097 3) Connect the exposed pad of the IC to the SGND plane. Do not make a direct connection between the exposed pad plane and SGND (pin 2) under the IC. Connect the exposed pad and pin 2 to the SGND plane separately. Connect the ground connection of the feedback resistive divider, the soft-start capacitor, the adjustable reset timeout capacitor, and the compensation network to the SGND plane. Connect the SGND plane and PGND plane at one point near the input bypass capacitor at VIN. 4) Use the large SGND plane as a heatsink for the MAX5096/MAX5097. Use large PGND and LX planes as heatsinks for the rectifier diode and the inductor. 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 MAX5096/MAX5097 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode PACKAGE OUTLINE, 16, 20, 28, 32, 40L THIN QFN, 5x5x0.8mm 21-0140 18 ______________________________________________________________________________________ K 1 2 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode PACKAGE OUTLINE, 16, 20, 28, 32, 40L THIN QFN, 5x5x0.8mm 21-0140 K 2 ______________________________________________________________________________________ 2 19 MAX5096/MAX5097 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.) 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.) TSSOP 4.4mm BODY.EPS MAX5096/MAX5097 40V, 600mA Buck Converters with LowQuiescent-Current Linear Regulator Mode XX XX PACKAGE OUTLINE, TSSOP, 4.40 MM BODY, EXPOSED PAD 21-0108 E 1 1 Revision History Pages changed at Rev 1: 1, 2, 3, 5, 20 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. 20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2007 Maxim Integrated Products Boblet is a registered trademark of Maxim Integrated Products, Inc.