19-3966; Rev 2; 3/96 MAALVI +12V/+15V Step-Up Current-Mode General Description The MAX732/MAX733 are CMOS step-up DC-DC switch- mode regulators. The MAX732 is a +12V regulator that accepts inputs from 4.0V to 9.3V and delivers up to 200mA of DC current. The MAX733 is a +15V regulator that delivers up to 125mA and accepts inputs from 4.0V to 11.0V. Typical full-load efficiencies are 85% to 92%. They require only a single inductor value of 50uH to function over their entire ranges, so no inductor-related design is necessary. Accuracy is guaranteed over temperature; line, and load variations. The MAX732/ MAX733 use a current-mode pulse-width modulation (PWW) controller to provide precise output regulation and low subharmonic noise. Typical no load supply current is 1.7mA. Fixed 170kHz oscillator frequencies allow easy filtering of ripple and noise and provide for small external components. The MAX732/MAX733 feature cycle-by-cycle current limiting, overcurrent limiting, undervoltage lockout, and programmable soft-start protection. For an adjustable version of these devices, refer to the MAX752 data sheet. For lower-power step-up applica- tions, refer to the MAX632/MAX633 and MAX642/ MAX643 data sheets. For more applications information, refer to AN-4.1, MAX732 EV Surface-Mount Evaluation Board and Flash EEPROM Power Supply Application Notes. Applications Flash Memory Programming Power Supply Portable Instruments Distributed Power Systems Computer Peripherals DC-DC Converter Module Replacement ; . ; . ; Top View = Spon 1) v+ Typical Application Circuit VREF Z| waaxim 17) Vout MAX732 3 6] LX 8s MAX733 fe) ce & rs] GND +4.0V TO +9.3V DIP V+ SHDN Nc. Gj @ 76) V+ MAXI LX > 12 SHON [2] 73) N.C. MAX732 VREF G3] 74) Vout Vout N.C. ] maxim [a] LX $8 E MAXT32 nz) LX SS GND VREF| x co fey MAX7S9 Fin ix In? > 1: GND [7 Ho) N.C. Ty TT a GND (SWITCH) [=] GND (SWITCH) = *OPTIONAL CAPACITORS so MAXIMA Maxim Integrated Products 1 PWM Regulators Features @ Load Currents Guaranteed to 200mA with No External MOSFET (125mA for MAX733) 170kHz High-Frequency Current-Mode PWM @ Small Inductor and No Component Design Required @ 85% to 92% Typical Efficiencies at Full Load @ Overcurrent and Soft-Start Protection @ 8-Pin DIP, 16-Pin Wide SO Packages Step-Up from a 4.0V Input @ Shutdown Pin Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX732GPA 0C to +70C 8 Plastic DIP MAX732CWE 0C to +70C 16 Wide SO MAX732C/D 0C to +70C Dice* MAX732EPA -40C to +85C 8 Plastic DIP MAX732EWE -~40C to +85C 16 Wide SO MAX732MJA -55C to +125C 8 CERDIP MAX733GPA 0C to +70C 8 Plastic DIP MAX733CWE 0C to +70C 16 Wide SO MAX733C/D 0C to +70C Dice* MAX733EPA -40C to +85C 8 Plastic DIP MAX733EWE ~40C to +85C 16 Wide. SO MAX733MJA -55C to +125C 8 CERDIP *Contact factory for dice specifications. Pin Configurations For free samples & the latest literature: http:/;www.maxim-ic.com, or phone 1-800-998-8800 SCELXVW/CELXVW|MAX732/MAX733 +12V/+15V Step-Up Current-Mode PWM Regulators ABSOLUTE MAXIMUM RATINGS Pin Voltages VE LX Lecce cece cece e cece eet eee tenn eenenes VOUT cnc eee eee e eee nene SS, CC, SHDN Peak Switch Current (ILx) Reference Current (IvREF) Continuous Power Dissipation (Ta = +70C) Plastic DIP (derate 6.9mW/C above +70C) ....... 550mW Wide SO (derate 9.5mW/C above +70C) ......... 760mW CERDIP (derate 8.0mW/C above +70C) .......... 640mwW Operating Temperature Ranges: MAX7T3_C_ oo cee ee eee eee eee es 0C to +70C. MAX73_E__ owe ccc cence eens -40C to +85C MAX73_MJA 20... cece cece e eee tenes -56C to +125C Junction Temperatures: MAX73_C_/E__ oo cece ccc e renee ene nee ees +150C MAX73_ MUA oo... ccc eee cere eter tener en nes +176C Storage Temperature Range ............... -65C to +160C Lead Temperature (soldering, 10sec) ............... +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 devices at these or any 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 2, V+ = 5V, ILOAD = OMA, Ta = TaIN to TMax, Unless otherwise noted, typical values are at Ta = +25C.) MAX732 MAX733 PARAMETER CONDITIONS MIN TYP MAX | MIN TYP MAX | UNITS V+ = 4.5V to 9.3V, MAX732C/E 11.52 12.0 12.48 0<ILoAD <150mMA | MAX732M 1140 120 12.60 V+ = 6V to 9.3V, MAX732C/E 11.52 120 12.48 Output Voltage O<ILoaD <200mA =| MAx732M 11.40 120 12.60 V Oe hoa 100m 4 | MAX733C/E/M 14.25 150 15.75 vehon sosma | MAX733C/E/M 14.25 15.0 15.75 Input Voltage Range 40 93 40 ma Vv V+ = 4V to 9.3V 0.20 Line Regulation %/V V+ = 4V to 11V 0.20 Load Regulation ILOAD = OMA to 100mMA 0.0035 0.0035 %/mA Efficiency V+ = 5V, ILoaD = 100mA 88 88 % Supply Current includes switch current 17 3.0 1.7 3.0 mA SHDN = 0, Entire circuit 70 100 55 100 Standby Current uA SHDN = 0, Into V+ 6 6 Shutdown Input Vin (Note 1) 20 _ 2.0 V Threshold Vit (Note 1) 0.25 0.25 een t0 0 un Short-Circuit Current 15 15 A Undervoltage Lockout 3.7 4.0 37 40 Vv 3-178. MAK ijl+12V/+15V Step-Up Current-Mode PWM Regulators __.. ELECTRICAL CHARACTERISTICS (continued) , MAX732 MAX733 PARAMETER CONDITIONS MIN TYP MAX MIN TYP . MAX | UNITS LX On Resistance ILx = 500mA 0.5 0.5 : Q LX Leakage Current Vos = 12V 1.0 1.0 uA Reference Voltage 1.16 1.23 1.30 1.15 1.23 1.30 v Reference Drift Ta = TmIn to TMAX 50 50 ppm/C Oscillator Frequency 130 170 210 130 170 210 kHz Tanegensation Pin 7500 7500 Note 1: Shutdown input thresholds not tested, but guaranteed by design. EELXVN/ZELXUN Typical Operating Characteristics SWITCHING WAVEFORMS SWITCHING WAVEFORMS CONTINUOUS CONDUCTION DISCONTINUOUS CONDUCTION MAX732 LINE TRANSIENT RESPONSE a a a c ct 100ms/div Qusidiv A: Switch Voltage (LX pin), 5V/div, A: Switch Voltage (LX pin), 5V/div, A: Vout, 50mV/div, DC-Coupted OV to +12.4V OV to +12.4V B: V+, 5V/div, 6.0V to 9.0V B: Inductor Current, 500mA/div B: Inductor Current, 200mA/div Circuit of Fig. 2, lout = 200mA, C: Output Voltage Ripple, 50mV/div C: Output Voltage Ripple, 50mV/div Ta = +25C MAX732, Circuit of Fig. 2, Cour = 300uF, MAX732, Circuit of Fig. 2, Cour = 300uF, V+ = +5V, lout = 100mA, Ta = +25C V+ = +8, lout = 20mA, Ta = +25C MAX733 LINE TRANSIENT RESPONSE MAX732 LOAD TRANSIENT RESPONSE MAX733 LOAD TRANSIENT RESPONSE oe 100ms/div 50ms/div 50ms/div A: Vout, 50mV/div, DC-Coupled A: Vout, S0mV/div, DC-Coupled A: Vout, 50mV/div, DC-Coupled B: V+, 5Wdiv, 6.0V to 12.0V B: lout, 100mA/div, 10mA to 200mA B: lout, 50mA/div, 10mA to 125mA Circuit of Fig. 2, lout = 125mA, Circuit of Fig. 2, V+ = +6V, Ta = +25C Circuit of Fig. 2, V+ = +6V, Ta = +25C Ta = +25C MAXISI 3-179+12V/+15V Step-Up Current-Mode PWM Regulators Typical Operating Characteristics (cont'd) Ly] MAX732 EFFICIENCY MAX733 EFFICIENCY NO-LOAD SUPPLY CURRENT & vs. OUTPUT CURRENT vs. OUTPUT CURRENT vs. SUPPLY VOLTAGE d< 100 100 2 < a S| pe c = _ V+ = 9V z UNDERVOLTAGE # 90 ent LOCKOUT ~ = LL V+ = 6V 5 3 > 3 HYSTERESIS a Z2 L > 1 + + N 2 3 i & UNDERVOLTAGE iG 80 x 80 Vt = 4V na LOCKOUT i) 2 | ENABLED N OF CIRCUIT OF FiG. 2,1 3 CIRCUIT OF FIG. 2, *< = 425C Ta = +25C = lout = 0, Ta = +25C 70 70 1 1 0 i 1 1 <x 0 50 100 150 200 250 300 0 100 =. 200 S300 400 0 2 4 6 8 0 2 = _ QUTPUT CURRENT (mA) OUTPUT CURRENT (mA) SUPPLY VOLTAGE (V) MAX732 PEAK INDUCTOR CURRENT MAX733 PEAK INDUCTOR CURRENT OSCILLATOR FREQUENCY vs. OUTPUT CURRENT vs. OUTPUT CURRENT vs. SUPPLY VOLTAGE 1000 1200 180 = 4 _~ ~ E 00 4 E 1000 = 5 V+ =v 5 3 = 600 1 ce 800 -+v+ = 6V tj 170 > =a D2 V+ =9V y | vs =ov S = OA Aven = 600 }V+= AAT Fs 3 LT CIRCUIT OF FIG. 2, 3 7 | CIRCUIT OF Fic. 2, 5 se 200 L1 = SOuH, xs L1 = 50uH, 5 Ss C4 = 300uF, = 200 CA = 2006, 2 CIRCUIT OF FIG. 2, a Ta = +25C o Ta = +25C Ta = +25C 0 ii 0 150 0 100 200 300 400 0 100 200 300 400 500 2 4 6 8 0 2 1 QUTPUT CURRENT (mA) OUTPUT CURRENT (mA) SUPPLY VOLTAGE (V) MAXIMUM OUTPUT CURRENT vs. SUPPLY VOLTAGE an gS oO 400 MAX733 300 1} MAX732 np S S 3S S CIRCUIT OF FIG. 2, Ta = +25C MAXIMUM OUTPUT CURRENT (mA) Q 2 4 6 8 0 12 14 SUPPLY VOLTAGE (V) 3-180 MA AA. 44+12V/+15V Step-Up Current-Mode PWM Regulators Pin Description PIN # PIN # 16-PIN 8-PIN DIP WIDE SO NAME FUNCTION 1 2 SHDN Shutdownactive low. Ground to power-down chip, tie to V+ for normal operation. Output power FET is held off when SHDN is low. VREF Reference Voltage Output (+1.23V). Supplies up to 100A for external loads. ss Soft-Start. Capacitor between SS and GND provides SS and short-circuit protection. cc Compensation Capacitor Input. Externally compensates the outer feedback loop. 7 GND Ground. Ground for control circuitry. 8,9 GND (SW) Switch Ground. Ground of the output power FET. Both pins must be separately tied to ground because they are not internally connected. 11, 12, 13 LX Drain of internal N-channel power MOSFET. 14 Vout Output-Voltage Sense Input. Provides regulation feedback sensing. Connect to +12V or +15V output. 8 16 V+ Supply Voltage Input. Bypass to GND with 0.1uF ceramic and large-value electrolytic capacitors in parallel. The 0.1yF capacitor must be as close to the device as possible. 1, 4, 10, 15 N.C. No Connect. No internal connections to these pins. Table 1. Typical Soft-Start Times MAX732 CIRCUIT CONDITIONS SOFT-START TIME (ms) vs. C1 (uF) V+ (V) lout (mA) C4 (uF) 0.1pF 0.47 pF 1.0uF 45 0 300 57 ms 115 ms 123 ms 6.0 0 300 40 80 70 9.0 0 300 29 57 44 45 100 300 92 348 780 6.0 100 300 59 209 444 9.0 100 300 29 57 60 45 200 300 175 713 1690 6.0 200 300 84 340 756 9.0 200 300 28 76 123 MAX733 CIRCUIT CONDITIONS SOFT-START TIME (ms) vs. C1 (uF) V+ (V) lout (mA) C4 (uF) OAuF 0.47yF 1.0uF 45 0 300 90 ms 208 ms 251 ms 6.0 0 300 64 135 148 9.0 0 300 36 67 53 12.0 0 300 28 49 33 45 75 300 157 680 1380 6.0 75 300 103 426 882 9.0 75 300 46 162 305 12.0 75 300 28 49 33 45 125 300 235 1124 2260 6.0 125 300 133 596 1255 9.0 125 300 54 231 476 12.0 125 300 30 49 41 Note: Soft-start times are + 35% accurate, C1 is the soft-start capacitor, C4 is the output capacitor. MAKIM: ECLXVN/CELXVNMAX732/MAX733 #182, +12V/+15V Step-Up Current-Mode PWM Regulators v MAX732 MAX733 in yl Lal "05 Vin =+4.0V 10 +9.3V Vin= +4.0V TO +11.0V Vout = +12V Vout = +18V O.1F I rt 1504F SHON V+ UNDERVOLTAGE BIAS LOCKOUT Vout GEN ya 4 LL I 4.0V ots Toc ERROR AMP PWM COMPARATOR pz | c7 1.23V 5 D>. Vout ary BANDGAP 300uF kt = vrer} = ae CURRENT SENSE AMP SLOPE COMPENSATION OVERCURRENT COMPARATOR Figure 1. MAX732/MAX733 Detailed Block Diagram with External Components Operating Principle The MAX732 +12V switch-mode regulator uses a current- mode pulse-width modulation (PWM) control system coupled with a simple boost regulator topology to convert an unregulated DC voltage ranging from 4.0V to 9.3V toa +12V output. The MAX733 operates likewise, stepping up to +15V from a 4.0V to 11.0V supply. The current-mode PWM architecture provides cycle-by-cycle current limiting and excellent load-transient response characteristics. _CCW@?S tse Description The controller consists of two feedback loops: an inner (current) loop that monitors the switch current via the current-sense resistor (Rg) and amplifier, and an outer (voltage) loop that monitors the output voltage via the error amplifier (Figure 1). The inner loop performs cycle-by-cycle current limiting, truncating the power transistor on-time. when the switch current reaches a predetermined threshold. This threshold is determined by the outer loop. For example, a sagging output voltage produces an error signal that raises the threshold, allowing the circuit to store and transfer more energy during each cycle. Programmable Soft Start A capacitor connected to the Soft-Start (SS) pin ensures an orderly power-up. The voltage on the charging capacitor slowly raises the clamp on the error-amplifier output voltage, limiting surge currents at power-up by slowly increasing the cycle-by-cycle current-limit thresh- old. Soft-start timing is controllable from SS by capacitor choice. A typical value is 0.1uF. Table 1 lists timing characteristics for selected capacitor values and circuit conditions. The output sags if more than the maximum load current is drawn. The overcurrent comparator trips if the load exceeds approximately 1.5A. An SS cycle is actively initiated when either an undervoltage or overcurrent fault condition triggers an internal transistor to discharge the SS capacitor to ground. Overcurrent Limiting When the load current exceeds approximately 1.5A, the output stage is turned off by the inner loop cycle-by- cycle current-limiting action, and the overcurrent com- parator signals the control logic to initiate an SS cycle. On each clock cycle, the output FET turns on again and attempts to deliver current until cycle-by-cycle or over- current limits are exceeded. Note that the SS capacitor must be at least 0.01uF for overcurrent protection to function properly. MAXIM+12V/+15V Step-Up Current-Mode PWM Regulators INPUT > c5* cc 4 0.15 pF SS__GND__VREF 5 2 LE og C1 c7* 3 oruFL__|_ [oorur J 22000 NOTE: PIN NUMBERS REFER TO 8-PIN PACKAGES . Se u pant | INPUT SUPPLY | OUTPUT | RUARANTEED ca ct fu RANGE (V) | VOLIAGE | OUTPUT CURRENT 8 otpr | 350uF IH Dn 45109.3 | +12V 150mA SHDN LX p OUTPUT MAXT32 6.0 to 9.3 +12V 200mA MAXIM 45to11.0 | +15V 100mA MAX732 7 MAXT33/ Vour-* otto | +15v 200mA max733 "YT C4" OPTIONAL LOWPASS OUTPUT FILTER tt sth FILTER HL OUTPUT L2 cg OUTPUT - 25uH aL 22 * FOR MAX73_E OR MAX73_M, C5 AND C7 ARE NOT REQUIRED, C3 AND C4 SHOULD BE LOW-ESR CAPACITORS (SUCH AS OS-CON SERIES), AND C6 SHOULD BE 4.71. Figure 2. Standard Boost Application Circuit Undervoltage Lockout The MAX732/MAX733 monitor the supply voltage at V+ and operate for supply voltages greater than 3.7V (typ), 4.0V guaranteed, with 0.25V hysteresis (see MAX732 Quiescent Supply Current vs. Supply Voltage, Typical Operating Characteristics). When an undervoltage condition is detected, control logic turns off the output power FET and discharges the SS capacitor to ground. The control logic holds the output power FET in an off state until the supply voltage rises above the undervoltage threshold, at which time an SS cycle begins. Shutdown The MAX732/MAX733 are held in shutdown mode by keeping SHDN at ground. In shutdown, the output power FET is off, but there is still an external path from V+ to the load via the inductor and diode. There is also a path from V+ to GND via the inductor, diode, and internal feedback resistors at the Voy7 pin. The internal reference also turns off, which causes the SS capacitor to discharge. Typical device standby current in shutdown mode is 6A. For normal operation, connect SHDN to V+. An SS cycle is initiated when the MAX732/MAX733 come out of shutdown. Internal Reference The +1.23V bandgap reference supplies up to 100nA at VREF. A bypass capacitor from VREF to GND may be required. Oscillator The. internal oscillator typically operates at 170kHz. Temperature stability over the military temperature range is about 0.06%/C. PAMXILSAA Applications Information Standard +12V or +15V Output Step-Up Converter Application in Continuous-Conduction Mode Figure 2 shows the standard +12V or +15V step-up application circuit for continuous-conduction mode operation. This circuit will operate over its entire line, load, and temperature ranges using the single set of component values shown. All components shown are suitable for both the MAX732 and the MAX733. The MAX732 delivers a guaranteed 150mA for 4.5V to 9.3V supply voltages, and a guaranteed 200mA for supplies from 6.0V to 9.3V. The MAX733 is guaranteed to deliver 100mA for inputs ranging from 4.5V to 11.0V and 125mA for inputs from 6.0V to 12.0V. Both devices regulate at supply voltages down to 4.0V (the upper limit of undervoltage lockout), but some reduction of the maximum output current will occur. Continuous-conduction mode operation gives a cleaner output than discontinuous operation. Peak-to-peak ripple amplitude is minimized and ripple frequency is fixed at the oscillator frequency. Both conditions make the output noise easy to filter. However, continuous-conduction mode operation requires additional compensation and bypass capacitors, as shown in Figure 2. For extended and military temperature range applications, C3 and C65 (in Figure 2) should be low-ESR capacitors. When OS-CON capacitors are used, no compensation is necessary, so C5 and C7 are not required. However, the reference bypass capacitor C6 should be at least 4.7pF. Figure 2 shows an example using through-hole components. Figure 3 shows an example of a power supply designed with surface-mount components. 3-183 |SEZLXVW/ZELXVNMAX732/MAX733 +12V/+15V Step-Up Current-Mode PWM Regulators +4V TO +9.3V TO FLASH 18H MEMORY _ V+ Vpp PIN Vy SHDN LX > PP +12V +4% PROGRAMMING MAXI/VI 1N5817 @ 120mA CONTROL MAX732 (DIRECT Vout T FROM yP) 5000pF | + end CC | =e 33uF { VBATT +1,.8V TO +5V +5 + on 33u4F 150uF rz ath _ aon - INS817 Vep LX rr, PROGRAMMING | IAxI~vI PP CONTROL MAX732 PROGRAMMING (DIRECT VOLTAGE FROM uP) Vout H12V 4% a CC 0.1yF , @ BOA SS_GND VREF 680uF AS a 0.047 uF = QuF Figure 3. Flash Memory Programmer V+ BYPASS REQUIREMENTS MAX733 applications should place capacitor C2 (Figure 2) to within 1/2 inch from the V+ and GND pins of the IC. This capacitor helps snub high voltages created by large load transients. +12V Flash Memory Programming Power Supply The circuit of Figure 3 is a simple +12V 44%, 120mA flash memory programmer. The small 18H inductor forces the circuit to operate in discontinuous-conduction mode, which allows for smaller input and output filter capacitors and the removal of several bypass and compensation capacitors relative to the standard application. It also makes the circuit less sensitive to PC layout errors. Programming is controlled by a direct microprocessor input to the SHDN pin of the MAX732. When SHDN is forced high, the output voltage, which is connected to the Vpp input of the flash memory, rises to +12V and programs the flash memory. When SHDN goes low, the output voltage drops to approximately a diode drop below Vx. The voltage at the Vpp pin has to be kept below 6.5V to avoid inadvertent programming. For a +5V input, efficiency is 88%, quiescent current for this circuit is 1.7mA, circuit shutdown current is 70pA, and shutdown current into the V+ pin is 6A. See Application Note 4.2. 2-Cell to +12V Battery-Powered Flash Memory Programming Supply The circuit of Figure 4 allows for +12V step-up operation with battery supplies as low as 1.8V. The MAX732 supply voltage (V+) and programming control pin (SHDN) operate from the +5V logic supply, while the voltage across the inductor is supplied directly from the battery. Figure 4. 2-Cell to +12V Battery-Powered Flash Memory Programmer This application is targeted for 60mA operation. It is not possible to achieve output currents greater than 80mA with Veatr below 2.0V because of the high peak currents required. Inductor Selection The MAX732/MAX733 require no inductor design. They are tested in-circuit, and are guaranteed to deliver the power specified in the Electrical Characteristics with high efficiency using a single 50uH inductor. A 47H inductor can also be used. The 50nH inductor's incremental saturation current rating should be greater than 500mA for 200mA load operation. For lower power applications, smaller inductor values may be used. Table 2 shows recommended inductor types and suppliers for various applications. The listed surface- mount inductors efficiencies are nearly equivalent to those of the jarger-sized, through-hole inductors. Output Filter Capacitor Selection The primary criterion for selecting the output filter capacitor is low equivalent series resistance (ESR). The product of the inductor current variation and the ESR of the output capacitor determines the amplitude of the high-frequency ripple seen on the output voltage. The ESR of the capacitor should be less than 0.25Q to keep the output ripple less than 50mV,,,, over the entire current range (using a 50uH inductor). In addition, the ESR of the output filter capacitor should be minimized to maintain AC stability. Refer to Table 2 for suggested capacitor suppliers. In the standard application of Figure 2, the output capacitor value should be at least 300pF in order to maintain stability at full loads. 150uF capacitors (MAXCO001) are available from Maxim in production quantities. Two of these capacitors can be connected in MAXIM+12V/+15V Step-Up Current-Mode Table 2. Component Suppliers PWM Regulators PRODUCTION METHOD INDUCTORS CAPACITORS Surface Mount Sumida (847) 956-0666 CDS4-470 (47H) CD54-180 (18H) for discontinuous mode Coiltronics (561) 241-7876 CTX 100-series Matsuo (714) 969-2491 267-series Miniature Through-Hole RCH654-470 Sumida (847) 956-0666 Sanyo (619) 661-6835 OS-CON-series Low ESR Organic Semiconductor Low-Cost Through-Hole RL 1284-47 Renco (516) 586-5566 Maxim MAXC001 150uF, Low ESR Electroyltic Nichicon (847) 843-7500 PL-series Low ESR Electrolytics United Chemicon (714) 255-9500 LXF-series parallel. Lighter loads require proportionately lesser capacitor values. For operation below -10C, OS-CON series capacitors are suitable when using through-hole components. Other Components The catch diode should be a Schottky or high-speed silicon rectifier with a current rating of at least 500mA for full-load (200mA) operation. The 1N5817 is a good choice. The two compensation capacitor (CC) values at the CC input are critical because they have been selected to provide the best transient responses. Output Ripple Filtering An optional lowpass pi-filter (Figure 2) can be added to the output to reduce output ripple to about 5mVp.p. The cutoff frequency of the filter shown is 21kHz. Since the filter inductor is in series with the circuit output, its resistance should be minimized to avoid excessive voltage drop. Figure 5. Surface-Mount PC Layout for Standard Step-Up Application (1x Scale, .Top-Side Trace View) Figure 6. Surface-Mount PC Layout for Standard Step-Up Application (1x Scale, Bottom-Side Trace View) EELXVN/CELXVNMAX732/MAX733 +12V/+15V Step-Up Current-Mode PWM Regulators \ mez Figure 7. Surface-Mount Drilling Guide for Standard Step-Up Application. All Holes are 0.031 in diameter. (1x Scale, Top-Side Trace View) Printed Circuit Layouts Agood layout is essential to clean, stable operation. The surface-mount layout and component placement diagrams in Figures 5-8 have been successfully tested over a wide range of operating conditions. The surface- mount layout shown is configured for the Sumida and Matsuo surface-mount components listed in Table 2. Note that the input bypass capacitors must be positioned as close to the Voyt and GND pins as possible. The traces connecting the ground to the input and output filter capacitors and the MAX732/MAX733 GND pin must be short to reduce stray inductance. 3-186 Figure. 8. Surface-Mount Component Placement Diagram for Standard Step-Up Application. Component Labels Refer to Figure 9 MAX732 Evaluation Board An assembled surface-mount printed circuit board is available for the MAX732. Intended for prototyping and performance evaluation, this board is a +12V switched power supply capable of delivering 120mA. The evalua- tion board circuit is configured as the flash memory programmer shown in Figure 9, and contains all components, including a miniature surface-mount inductor and tantalum filter capacitors on a printed circuit layout similar to Figures 5-8. Also included on the board is a P-channel MOSFET switch for applications that require total turn-off of the MAX732 output. The evaluation board can be ordered as part number MAX732EVKIT. For more information about the MAX732 evaluation board refer to AN-4.1, MAX732 EV Surface-Mount Evaluation Board and Flash EEPROM Power Supply Application Notes. MAXIM+12V/+15V Step-Up Current-Mode PWM Regulators INPUT 4V TO 9.3V > a 1 aguF Vpp CONTROL Nic V+ INPUT 1.23V L. y$ SHDN| REF N/C ,__|WREF Vout t D1 = | ce IN5817 _|Nec . LX pr \ / 3 LX C2 it 8S i 33uF T cc LX Ww = CURRENT- ->4 MODE NIC GNO} PWM [ > < $ |cnp GND Axim iL Max7z2 oe | cot 1k = Ce c3 OPTIONAL CAPACITORS = 5"F | I | OUTPUT \ SWITCH | CONTROL | OPTIONAL OUTPUT SWITCH OUTPUT ; 42V @ 120mA Figure 9. Circuit Schematic for Surface-Mount Evaluation Board MAKIN 3-187 CELXVN/CELXVNMAX732/MAX733 +12V/+15V Step-Up Current-Mode PWM Regulators MAX732/MAX733 Vout = Vout (MAX732) 0.123" (3.124 mm) GND GND(SW) GND(SW) 0.114 (2.895 mm) NOTE: CONNECT SUBSTRATE TO V+ TRANSISTOR COUNT: 226 Chip Topography 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 12 1996 Maxim Integrated Products Printed USA MAAXLM. is a registered trademark of Maxim Integrated Products.