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MAXIM MAX1776 24V 600mA Internal Switch 100% Duty Cycle Step-Down Converter handbook

1. Typical Operating Circuit Pin Configuration TOP VIEW AVLAZCLAVI 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 Maxim Integrated Products 1 9 7Z LXVM MAX1776 24V 600mA Internal Switch 100 Duty Cycle Step Down Converter ABSOLUTE MAXIMUM RATINGS IN SHDN ILIM ILIM2 to GND sala a eects 0 3V to 25V 2V to VIN 0 3V ipti bed 0 3V to 6V OUT FB to GND Peak Input Current Maximum DC Input Current 500mA Continuous Power Dissipation TA 70 C 8 Pin UMAX derate 4 1mW C above 70 O 330mW Operating Temperature Range ssss 40 C to 85 C Junction Temperature Storage Temperature Range sssssss 65 C to 150 C Lead Temperature soldering 10s 300 C 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 Circuit of Figure 1 Vin 12V SHDN IN Ta 0 C to 85 C unless otherwise noted PARAMETER SYMBOL Input Voltage Range VIN CONDITIONS MIN No
2. nal current sensing and a high switching frequency minimize PC board space and component costs INPUT OUTPUT 4 5V TO 24V 5V SHDN MAXUM ILIM MAX1776 g Cin 10uF 25V CERAMIC SEE TABLE 3 FOR OTHER COMPONENT VALUES NOTE HIGH CURRENT PATHS SHOWN WITH BOLD LINES Figure 1 Typical Application Circuit 8 Current Limited Control Architecture The MAX1776 uses a proprietary current limited control scheme with operation to 100 duty cycle This DC DC converter pulses as needed to maintain regulation resulting in a variable switching frequency that increas es with the load This eliminates the high supply cur rents associated with conventional constant frequency pulse width modulation PWM controllers that switch the MOSFET unnecessarily When the output voltage is too low the error comparator sets a flip flop which turns on the internal P channel MOSFET and begins a switching cycle Figure 2 As shown in Figure 3 the inductor current ramps up linear ly storing energy in a magnetic field while charging the output capacitor and servicing the load The MOSFET turns off when the peak current limit is reached or when the maximum on time of 10us is exceeded and the out put voltage is in regulation If the output is out of regula tion and the peak current is never obtained the MOSFET remains on allowing a duty cycle up to 100 This feature ensures the lowest possible dropout volt age Once the MOSFET turns off the
3. where VFB 1 25V and VOUTPUT may range from 1 25V to VIN Setting Current Limit The MAX1776 has an adjustable peak current limit Configure this peak current limit by connecting ILIM and ILIM2 as shown in Table 1 INPUT OUTPUT 4 5V TO 24V 1 25V TO Vin MAXIM ILIM MAX1776 Figure 4 Adjustable Output Voltage 10 Table 1 Current Limit Configuration ILIM2 CONNECTED TO CURRENT ILIM LIMIT mA CONNECTED TO Choose a current limit that realistically reflects the maxi mum load current The maximum output current is half of the peak current limit Although choosing a lower current limit allows using an inductor with a lower cur rent rating it requires a higher inductance see Inductor Selection and does little to reduce inductor package size Inductor Selection When selecting the inductor consider these four para meters inductance value saturation rating series resistance and size The MAX1776 operates with a wide range of inductance values For most applica tions values between 10uH and 100uH work best with the controller s high switching frequency Larger induc tor values will reduce the switching frequency and thereby improve efficiency and EMI The trade off for improved efficiency is a higher output ripple and slower transient response On the other hand low value induc tors respond faster to transients improve output ripple offer smaller physical size and minimize cost If
4. E 3 E 3 U Vin 12V 6 3 5 80 E 5 RCUIT 1 3 3V 15 E S oo Vin 15V Vin 24V a E n E E 65 60 55 50 0 10 1 0 00 000 0 10 1 10 100 1000 7 8 9 10 11 12 13 14 15 16 lLoAp mA ILoAp mA Vin V SWITCHING FREQUENCY vs SWITCHING FREQUENCY vs LOAD CURRENT CIRCUIT 1 Vin CIRCUIT 1 VourPur ACCURACY vs TEMPERATURE E 15 E E 10 E 05 2 ce E cc _ Ww lu c 0 g d 2 amp ia L E 305 LOAD 10mA 1 0 15 0 100 200 300 400 500 600 700 800 900 25 40 20 0 20 40 60 80 100 lLoAp mA TEMPERATURE C MAKIM 5 MAX1776 24V 600mA Internal Switch 100 Duty Step Down Converter Cycle Typical Operating Characteristics continued Circuit of Figure 1 components from Table 3 Vin 2 4 12V SHDN IN TA 25 C QUIESCENT SUPPLY CURRENT vs TEMPERATURE QUIESCENT SUPPLY CURRENT vs SUPPLY VOLTAGE 18 0 g 14 20 1445 E S175 3 1410 i S 1405 amp 170 23 1400 oT a 165 g 1395 E O 13 90 Z 160 a 8 g 1385 S 155 13 80 13 75 15 0 13 70 40 20 0 20 40 60 80 5 7 9 1 18 15 17 19 21 23 25 EMPERATURE C SUPPLY VOLTAGE V PEAK SWITCH CURRENT LOAD TRANSIENT RESPONSE vs INPUT VOLTAGE CIRCUIT 3 0 3A CIRCUIT 5 0 8 E MAX1776 toc19 L 10uH e 07 B 1A L 06 L 22uH 0 05 E 10V B o E L 47uH amp
5. N 0 LOAD 50mA 1 3 1 0 0 6 5 7 9 11 18 15 17 19 21 23 25 5 7 9 1 13 15 17 19 21 23 25 ILoap A Vin V Vin V 4 MAXIM 24V 600mA Internal Switch 100 Duty Cycle Step Down Converter Typical Operating Characteristics continued Circuit of Figure 1 components from Table 3 Vin 12V SHDN IN TA 25 C Voutput vs Vin VourPUT VS Vin EFFICIENCY vs ligAp CIRCUIT 1 CIRCUIT 1 VoyrPUT 5V CIRCUIT 1 VOUTPUT 3 3V Vout 5V MAX1776 toc07 MAX1776 toc09 9 Z LXVM MAX1776 toc08 VourPur VourPur EFFICIENCY 96 5 7 9 di 13 15 17 19 21 23 25 5 7 9 1 13 15 17 19 21 23 25 0 10 10 100 1000 Vin V Vin V ILoAD mA EFFICIENCY vs lj gAp CIRCUIT 5 EFFICIENCY vs ILoap CIRCUIT 1 VourPur 3 3V VOUTPUT 3 3V 100 e E s Vin 6V E E
6. VDROPOUT CONDITIONS IOUT 525mA ILIM ILIM2 IN VIN 8V 24V 200Q load Load Regulation No load full load Digital Input Level Low SHDN ILIM2 S High Digital Input Leakage Current ILIM Input Level VSHDN VILIM VILIM2 0 or 24V VIN 24V High Thermal Shutdown 10 C hysteresis ELECTRICAL CHARACTERISTICS Circuit of Figure 1 Vin 12V SHDN IN TA 40 C to 85 C unless otherwise noted Note 1 PARAMETER Voltage Range SYMBOL VIN CONDITIONS Supply Current IN No load Supply Current in Dropout lIN DROP No load Shutdown Current Input Undervoltage Lockout Threshold Output Voltage Preset Mode VUVLO VOUT SHDN GND VIN rising VIN falling Feedback Set Voltage Adjustable Mode VFB OUT Bias Current T Pin Maximum Voltage FB Bias Current IFB FB Dual Mode Threshold Low LX Switch Minimum Off Time tOFF MIN LX Switch Maximum On Time tON MAX VFB 1 3V LX Switch On Resistance LIM2 GND GND ILIM2 IN VIN 6V ILIM2 GND LIM2 IN LIM2 GND GND ILIM2 IN IN ILIM2 GND ILIM2 IN LX Current Limit MAXIM ILIM ILIM2 GND ILIM GND ILIM2 IN ILIM IN ILIM2 GND ILIM ILIM2 IN 9 Z LXVM MAX1776 24V 600mA Internal Switch 100 Duty Cycle Step Down Converter ELECTRICAL
7. falls out of regulation For the typical application the maximum output current is approximately ILOAD MAX 1 2 ILX PEAK MIN For low input voltages the maximum on time may be reached and the load current is limited by ILOAD 1 2 VIN VoUT x 10us L Output Capacitor Choose the output capacitor to service the maximum load current with acceptable voltage ripple The output ripple has two components variations in the charge stored in the output capacitor with each LX pulse and the voltage drop across the capacitor s equivalent series resistance ESR caused by the current into and out of the capacitor VRIPPLE VRIPPLE ESR VRIPPLE C The output voltage ripple as a consequence of the ESR and output capacitance is VRIPPLE ESR ESRXIPEAK 2 Lx peak lourPur MN 2C OUT XVourPUT V VIN VOUTPUT VRIPPLE C where IPEAK is the peak inductor current see nductor Selection The worst case ripple occurs at no load These equations are suitable for initial capacitor selec tion but final values should be set by testing a proto type or evaluation circuit As a general rule a smaller amount of charge delivered in each pulse results in less output ripple Since the amount of charge deliv ered in each oscillator pulse is determined by the inductor value and input voltage the voltage ripple increases with larger inductance and as the input volt age decreases See Table 3 for recommended capaci
8. flip flop resets the inductor current is pulled through D1 and the current through the inductor ramps back down transferring the stored energy to the output capacitor and load The MOSFET remains off until the 0 42us minimum off time expires and the output voltage drops out of regulation MAXIM 24V 600mA Internal Switch 100 Duty Cycle MAXIMUM ON TIME DELAY MINIIMUM OFF TIME DELAY Figure 2 Simplified Functional Diagram LX WAVEFORM CIRCUIT 1 Vin 15V ILoap 500mA 50mV div 2us div Figure 3 Discontinuous Conduction Operation MAXIM Step Down Converter MAXIM MAX1776 Input Output Dropout Voltage A step down converter s minimum input to output volt age differential dropout voltage determines the lowest usable supply voltage In battery powered systems this limits the useful end of life battery voltage To maxi mize battery life the MAX1776 operates with duty cycles up to 100 which minimizes the dropout volt age and eliminates switching losses while in dropout When the supply voltage approaches the output volt age the P channel MOSFET remains on continuously to supply the load Dropout voltage is defined as the difference between the input and output voltages when the input is low enough for the output to drop out of regulation For a step down converter with 100 duty cycle dropout depends on the MOSFET drain to source on resistan
9. 03 yi AC COUPLED E L 1000H 50mV div a 02 500mA 01 10mA 0 0 5 10 15 20 25 10us div Vin V LINE TRANSIENT RESPONSE CIRCUIT 5 ILoap 50mA MAX1776 toc21 LINE TRANSIENT RESPONSE CIRCUIT 5 li gap 500mA MAX1776 toc20 AC COUPLED 200mv div AC COUPLED Vout Vout 200mv div 15V VIN 10V 10V VIN 5V T UL ML x IM u i I is 5V v UN mm m gn n Il M i BULL LLLA TIT 200us div 200us div AVLAZCLAVI 24V 600mA Internal Switch 100 Duty Cycle Step Down Converter Typical Operating Characteristics continued Circuit of Figure 1 components from Table 3 Vin 2 12V SHDN IN TA 25 C LX WAVEFORM CIRCUIT 1 STARTUP WAVEFORM CIRCUIT 1 Vin 15V ILoap 500mA RLOAD 1009 MAX1776 toc22 MAX1776 toc23 Vout 50mV div Vout 2us div 2us div EFFICIENCY vs lj gap CIRCUIT 3 Viy 12V EFFICIENCY vs lj gAp CIRCUIT 3 Viy 12V 100 a 100 m L 22uH i 2 o 9 c cS a amp e e E 8 L 4TuH H igi dS 80 80 75 75 0 10 1 10 100 1000 000 ILoAD mA AVLAX LA 7 9 7Z LXVM MAX1776 24V 600mA Internal Switch 100 Duty Cycle Step Down Converter Pin Description FUNCTION Dual Mode Feedback Input Connect to GND for the preset 5V ou
10. 19 1975 Rev 2 7 03 MI AALS 24V 600mA Internal Switch 100 Duty Cycle Step Down Converter Features General Description The MAX1776 high efficiency step down converter pro vides an adjustable output voltage from 1 25V to Vin from supply voltages as high as 24V An internal current limit ed 0 40 MOSFET delivers load currents up to 600mA Operation to 100 duty cycle minimizes dropout volt age 240mV at 600m4A The MAX1776 has a low 15yA quiescent current to Fixed 5V or Adjustable Output 4 5V to 24V Input Voltage Range Up to 600mA Output Current Internal 0 40 P Channel MOSFET Efficiency Over 95 improve light load efficiency and conserve battery life The device draws only 3pA while in shutdown High switching frequencies up to 200kHz allow the use of tiny surface mount inductors and output capaci tors The MAX1776 is available in an 8 pin UMAX pack age which uses half the space of an 8 pin SO For increased output drive capability use the MAX1626 MAX1627 step down controllers which drive an exter nal P channel MOSFET to deliver up to 20W 15pA Quiescent Supply Current 3pA Shutdown Current 100 Maximum Duty Cycle for Low Dropout Current Limited Architecture Thermal Shutdown Small 8 uMAX Package 9 9 9 9 9 9 FT 9 9 9 Applications Ordering Information Natehock Computes PART TEMP RANGE PIN PACKAGE Distributed Power Systems MAX1776EUA 40 C to 485 C 8 UMAX Keep Alive Supplies Hand Held Devices
11. CHARACTERISTICS continued Circuit of Figure 1 Vin 12V SHDN IN TA 40 C to 85 C unless otherwise noted Note 1 PARAMETER SYMBOL CONDITIONS LX Zero Crossing Threshold LX Switch Leakage Current VIN 24V LX GND Low High Digital Input Leakage Current VSHDN VILIM ViLIM2 0 or 24V VIN 24V Low Digital Input Level SHDN ILIM2 ILIM Input Level Note 1 Specifications to 40 C are guaranteed by design not production tested Typical Operating Characteristics Circuit of Figure 1 components from Table 3 VIN 12V SHDN IN TA 25 C LOAD REGULATION LOAD REGULATION CIRCUIT 1 Voutput 5V CIRCUIT 1 VOUTPUT 3 3V LOAD REGULATION CIRCUIT 2 0 6 s 0 2 3 E 4 3 0 E 0 2 02 VIN 24V gc E 5 a 5 Ee 5 Tapa be i Vin 12V 06 0 8 IN 08 40 Vin 15V 1 0 1 2 0 100 200 300 400 500 600 700 600 0 50 100 150 200 250 300 350 400 lLoAp mA ILoap mA lLoAp mA VourPUT VS VIN VourPUT VS VIN LOAD REGULATION CIRCUIT 5 CIRCUIT 5 Voyrpur 5V CIRCUIT 5 Voyrpur 3 3V 3 3 8 2 0 5 0 E 2 E 1 5 E F c i 10 0 E E lLoAp 1mA amp 0 E 0 05 lioap 10mA o i S 1 0 5 0 I o Be 2 0 5
12. Sunnyvale CA 94086 408 737 7600 13 2003 Maxim Integrated Products Printed USA MAXIM is a registered trademark of Maxim Integrated Products 9 Z LXVM
13. TORS Coilcraft www coilcraft com Coiltronics www cooperet com Pulse Engineering www pulseeng com Sumida USA www sumida com Toko www tokoam com 11 9 Z LXVM MAX1776 24V 600mA Internal Switch 100 Duty Cycle Step Down Converter Table 3 Recommended Components MAXIMUM LOAD CURRENT mA INPUT VOLTAGE V ILX PEAK CURRENT A CIRCUIT 10 to 24 1OUH 1 56A 70mQ Toko D75F 646FY 100M 1OUH 1 70A 48mQ Sumida CDRH6D28 100NC or 10UH 1 63A 55mQ Toko D75C 646CY 100M 0 055 INDUCTOR CAPACITOR 100uF 6 3V Sanyo POSCAP 6TPC100M 10 to 24 22uH 1 17A 120mO Toko D75F 646FY 220M 22uH 1 09A 115mQ Toko D75C 646CY 220M or 22uH 1 20A 95mQ Sumida CDRH6D28 220NC 47 F 6 3V Sanyo POSCAP 6TPA47M 10 to 24 10 to 24 47uH 0 54A 440m ida CDRH5D18 470 100puH 0 29A 766m ida CDRH4D28 101 Sum Sum 22uF 6 3V 1210 case Taiyo Youden JMK325BJ226MM 10pF 6 3V X7R 1206 case Taiyo Youden JMK316BJ106ML 5 to 5 44H 1 6A 56mQ ida CDRH5D18 5R4 10pH 1 04A 80mQ Toko D73LC 817CY 100M Sum 100uF 6 3V Sanyo POSCAP 6TPC 100m 47 F 6 3V Sanyo POSCAP 6TPA47M 22uH 0 41A 294mQ Sumida CDRH4D18 220 22yF 6 3V 1210 case Taiyo Youden JMK325BJ226MM Diode Selection The current in the external diode D1 in Figure 1 changes abruptly from zero to its peak value each time the LX swit
14. ce and inductor series resistance therefore it is propor tional to the load current VDROPOUT louT x RDS ON RINDUCTOR 9ZZELXVIN MAX1776 24V 600mA Internal Switch 100 Duty Cycle Step Down Converter Shutdown SHDN A logic low level on SHDN shuts down the MAX1776 converter When in shutdown the supply current drops to 3pA to maximize battery life and the internal P chan nel MOSFET turns off to isolate the output from the input The output capacitance and load current determine the rate at which the output voltage decays A logic level high on SHDN activates the MAX1776 Do not leave SHDN floating If unused connect SHDN to IN Thermal Overload Protection Thermal overload protection limits total power dissipa tion in the MAX1776 When the junction temperature exceeds TJ 160 C a thermal sensor turns off the pass transistor allowing the IC to cool The thermal sen sor turns the pass transistor on again after the IC s junc tion temperature cools by 10 C resulting in a pulsed output during continuous thermal overload conditions Design Information Output Voltage Selection The feedback input features dual mode operation Connect FB to GND for the 5 0V preset output voltage Alternatively adjust the output voltage by connecting a voltage divider from the output to GND Figure 4 Select a value for R2 between 10kQ and 100kQ Calculate R1 with the following equation R1 R2 x oyrur VEB
15. ch turns off To avoid excessive losses the diode must have a fast turn on time and a low forward voltage Make sure that the diode s peak current rating exceeds the peak current limit set by the current limit and that its breakdown voltage exceeds VIN Use Schottky iodes when possible 12 47uH 0 33A 230mQ Coilcraft DS1608C 473 10pF 6 3V X7R 1206 case Taiyo Youden JMK316BJ106ML MAX1776 Stability Instability is frequently caused by excessive noise on OUT FB or GND due to poor layout or improper com ponent selection Instability typically manifests itself as motorboating which is characterized by grouped switching pulses with large gaps and excessive low frequency output ripple during no load or light load conditions PC Board Layout and Grounding High switching frequencies and large peak currents make PC board layout an important part of the design Poor layout introduces switching noise into the feed back path resulting in jitter instability or degraded performance High power traces highlighted in the MAXIM 24V 600mA Internal Switch 100 Duty Cycle Typical Application Circuit Figure 1 should be as short and wide as possible Additionally the current loops formed by the power components CIN COUT L1 and D1 should be as short as possible to avoid radiated noise Connect the ground pins of these power components at a common node in a star ground configuration Separate the no
16. isy traces such as the LX node from the feedback network with grounded copper Furthermore keep the extra copper on the Step Down Converter board and integrate it into a pseudo ground plane When using external feedback place the resistors as close to the feedback pin as possible to minimize noise coupling Chip Information TRANSISTOR COUNT 932 PROCESS BiCMOS Package Information 4X S 8LUMAXD EPS INCHES MILLIMETERS DIM MIN MAX MIN MAX 0 043 1 10 FRONT VIEW NOTES 1 D amp E DO NOT INCLUDE MOLD FLASH 3 CONTROLLING DIMENSION MILLIMETERS 4 MEETS JEDEC MO 187C AA Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product No circuit patent licenses are 0 0256 BSC 0 65 BSC 0 116 0 120 295 3 05 H 0 188 0198 478 5 03 L 0016 0 026 041 066 1 a 0 6 0 6 BOTTOM VIEW S 0 0207BSC 0 5250 BSC TOP VIEW AFL SIDE VIEW 2 MOLD FLASH OR PROTRUSIONS NOT TO EXCEED 0 15MM 006 DDALLAS AVLAXKLAVI PROPRIETARY INFORMATION TITLE PACKAGE OUTLINE 8L uMAX uSOP DOCUMENT CONTROL NO REV 21 0036 J VA APPROVAL implied Maxim reserves the right to change the circuitry and specifications without notice at any time Maxim Integrated Products 120 San Gabriel Drive
17. load No load SHDN GND VIN rising 3 6 4 0 4 4 VIN falling 3 5 3 9 4 3 FB GND 4 80 5 00 5 20 Input Supply Current IIN Input Supply Current in Dropout lIN DROP Input Shutdown Current Input Undervoltage Lockout Threshold Output Voltage Preset Mode Feedback Set Voltage Adjustable Mode OUT Bias Current VouT 5 5V 1 65 3 5 6 25 OUT Pin Maximum Voltage 5 5 FB Bias Current IFB VFB 1 3V 25 25 FB Dual Mode Threshold Low 50 100 150 LX Switch Minimum Off Time tOFF MIN 0 22 0 42 0 62 LX Switch Maximum On Time tON MAX 8 10 12 1 6 3 2 VUVLO VOUT VFB 1 212 1 25 1 288 ND ILIM2 IN ILIM2 GND ND ILIM2 IN VIN 4 ILIM2 GND LX Switch On Resistance 0 5 0 95 150 180 300 360 600 720 1200 1440 LIM ILIM2 GND LIM GND ILIM2 IN LIM IN ILIM2 GND LIM ILIM2 IN LX Current Limit ILX PEAK LX Zero Crossing Threshold Zero Crossing Timeout LX does not rise above the threshold TA 25 C Ta 0 C to 85 C LX Switch Leakage Current Dual Mode is a trademark of Maxim Integrated Products Inc 2 MAXIM 24V 600mA Internal Switch 100 Duty Cycle Step Down Converter ELECTRICAL CHARACTERISTICS continued Circuit of Figure 1 Vin 12V SHDN IN TA 0 C to 85 C unless otherwise noted PARAMETER Dropout Voltage Line Regulation SYMBOL
18. the inductor value is too small the peak inductor current exceeds the current limit due to current sense com parator propagation delay potentially exceeding the inductor s current rating Calculate the minimum induc tance value as follows Vinmax VourPur X tON MIN IL X PEAK L MIN where tON MIN 1ps The inductor s saturation current rating must be greater than the peak switch current limit plus the overshoot due to the 250ns current sense comparator propaga tion delay Saturation occurs when the inductor s mag netic flux density reaches the maximum level the core can support and the inductance starts to fall Choose an inductor with a saturation rating greater than IPEAK in the following equation IPEAK ILX PEAK VIN VOUTPUT x 250ns L MAXIM 24V 600mA Internal Switch 100 Duty Cycle Step Down Converter Inductor series resistance affects both efficiency and dropout voltage see Input Output Dropout Voltage High series resistance limits the maximum current avail able at lower input voltages and increases the dropout voltage For optimum performance select an inductor with the lowest possible DC resistance that fits in the allotted dimensions Some recommended component manufacturers are listed in Table 2 Maximum Output Current The MAX1776 converter s output current determines the regulator s switching frequency When the convert er approaches continuous mode the output voltage
19. tor values and Table 2 for recommended component manufacturers SVAKIM Input Capacitor The input filter capacitor reduces peak currents drawn from the power source and reduces noise and voltage ripple on the input caused by the circuit s switching The input capacitor must meet the ripple current requirement IRMS imposed by the switching current defined by the following equation ILOADVOUTPUT x N 4 IRMS MN 3 VoUTPUT For most applications nontantalum chemistries ceram ic aluminum polymer or OS CON are preferred due to their robustness to high inrush currents typical of sys tems with low impedance battery inputs Alternatively connect two or more smaller value low ESR capacitors in parallel to reduce cost Choose an input capacitor that exhibits less than 10 C temperature rise at the RMS input current for optimal circuit longevity Table 2 Component Suppliers SUPPLIER WEBSITE Central Semiconductor www centralsemi com Fairchild www fairchildsemi com General Semiconductor www gensemi com International Rectifier www irf com Nihon On Semi www niec co jp engver2 niec co jp_eg htm www onsemi com Vishay Siliconix www vishay com brands siliconix main html Zetex www zetex com CAPACITORS AVX WWW avxcorp com Kemet www kemet com Nichicon www nichicon us com Sanyo Wwww sanyo com Taiyo Yuden www t yuden com INDUC
20. tput Connect to a resistive divider between OUT and GND to adjust the output voltage between 1 25V and VIN Ground Peak Current Control Input Connect to IN or GND to set peak current limit ILIM and ILIM2 together set the peak current limit See Setting Current Limit Inductor Connection Connect LX to external inductor and diode as shown in Figure 1 Input Supply Voltage Input voltage range is 4 5V to 24V Peak Current Control Input 2 Connect to IN or GND ILIM and ILIM2 together set the peak current limit See Setting Current Limit Shutdown Input A logic low shuts down the MAX1776 and reduces the supply current to 34A LX is high impedance in shutdown Connect to IN for normal operation Regulated Output Voltage High Impedance Sense Input Internally connected to a resistive divider Do not connect for output voltages higher than 5 5V Connect to GND when not used Detailed Description The MAX1776 step down converter is designed primar ily for battery powered devices and notebook comput ers The unique current limited control scheme provides high efficiency over a wide load range Operation up to 100 duty cycle allows the lowest pos sible dropout voltage increasing the usable supply voltage range Under no load the MAX1776 draws only 15pA and in shutdown mode it draws only 3pA to fur ther reduce power consumption and extend battery life Additionally an internal 24V switching MOSFET inter

MAXIM MAX1776 24V 600mA Internal Switch 100% Duty Cycle Step-Down Converter handbook

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