19-0017; Rev 1; 9/92 -5V/Adjustable, Negative-Output, Inverting, Current-Mode PWM Regulators General Description The MAX735 and MAX755 are CMOS, inverting switch- mode regulators with internal power MOSFETs. The MAX755 operates from a +2.7V to +9V input and generates an adjustable negative output; 1W output power is guaran- teed when powered from a +4.5V input. The MAX735 operates from a +4.0V to +6.2V output; 200mA output current is guaranteed for inputs greater than +4.5V. Qui- escent supply current for the MAX735 is typically 1.6mA, and a shutdown mode reduces this to 10HA. These power- conserving features, along with high efficiency and appli- cations circuits that lend themselves to miniaturization, make the MAX735/MAX755 excel in a broad range of on-card and portable-equipment applications. The MAX735/MAX755 employ a high-performance current- mode pulse-width modulation (PWM) control scheme to provide tight output-voltage regulation and low subhar- monic noise. The fixed-frequency oscillator is factory- trimmed to 160kHz, allowing for easy noise filtering. The regulators are production tested in actual application cir- cuits, and output accuracy is guaranteed to within +5% over all specified conditions of line, load, and temperature. The input-to-output differential of the MAX755 is limited to VIN + IVQuTI 11.7V. For an adjustable-output device with a wider input voltage range, refer to the MAX759 data sheet. For a fixed -SV part with a wider input voltage range, refer to the MAX739 data sheet. For fixed -12V and -15V versions, see the MAX736 and MAX737 data sheets. For lower-power applications, refer to the MAX635/636/637 data sheet. Applications Board-Level DC-DC Conversion Battery-Powered Equipment Computer Peripherals Typical Operating Circuit MAAI/VI Features @ Converts +2.7V to +9V Input to Adjustable Negative Output (MAX755) @ Converts +4.0V to +6.2V Input to 5V Output (MAX735) @ 1W Guaranteed Output Power (Vin 2 4.5V) @ 78% Typical Efficiency @ 1.6mA Quiescent Current (MAX735) @ 10.A Shutdown Mode @ 160kHz Fixed-Frequency Oscillator @ Current-Mode PWM - Low Noise and Jitter @ Soft-Start @ Simple Application Circuit Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX735CPA 0C to +70C 8 Plastic DIP MAX735CSA OC to +70C 8SO0 MAX735C/D 0C to +70C Dice* MAX735EPA -40C to +85C 8 Plastic DIP MAX735ESA -40C to +85C 8SO MAX735MJA -55C to +125C 8 CERDIP** MAX755CPA 0C to +70C 8 Plastic DIP MAX758CSA OC to +70C 8S0 MAX755C/D OC to +70C Dice* MAX755EPA -40C to +85C 8 Plastic DIP MAX755ESA -40C to +85C 850 MAX755MJA -55C to +125C 8 CERDIP** * Contact factory for dice specifications. ** Contact factory for availability and processing to MIL-STD-883. Pin Configuration VIN +4.0V 10 46.2 i. Vt Azur SHDN Vout MDa VREF MAX735 | Vout 10nF SS LX 14 y t cc 10yH | GNO wR aL ik 100uF /_-at-4 CIRCUIT USES TANTALUM SURFACE-MOUNT CAPACITORS. ____ TOP VIEW ee e san (4 MAAXILAA 13] Ve VREF | 2 MAX735 [7| LX na MAX755 7 3 6 | GND CC) 4 5 | Vout DIP/SO VIAL AKI SVI Maxim Integrated Products 1 Call toll free 1-800-998-8800 for free samples or literature. SSZLXUW/SELXVINMAX735/MAX755 -5V/Adjustable, Negative-Output, Inverting, Current-Mode PWM Regulators ABSOLUTE MAXIMUM RATINGS Supply Voltage (V+ to GND) MAX735............. +7V, -0.3V Operating Temperature Ranges: MAX755 (Note 1)..... +11, -0.3V MAX7_5C_ wee Switch Voltage (LX to V+)... 0. eee eee -12.5V, +0.3V MAX7_5E_ 8 cece cece eect ee ee Feedback Voltage (VoUTto GND) ............2.2.055 +25V MAX7_BSMJA 20 eee Auxiliary Input Voltages Junction Temperatures: (SS, CC, SHDN to GND) ............. -0.3V to (V+ + 0.3V) MAX7_5C/E__ Peak Switch Current (ILX) 2.6.60 eee 2.0A MAX7_5MJA 00 te Reference Current (IVREF) .. 2.00.0 ee 2.5mA Storage Temperature Range Continuous Power Dissipation (Ta = +70C) Lead Temperature (soldering, 10 sec) Plastic DIP (derate 9.09mW/C above +70C) ....... 727mW SO (derate 5.88mW/C above +70C).........-.-55 471mW CERDIP (derate 8.00mW/C above +70C).......... 640mWw 0C to +70C -40C to +85C -58C to +125C 4175C +300C Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (Circuit of Figure 2, V+ = 5V, -5.25V < VouT -4.75V, ILOAD = OMA, Ta = TMIN to TMAX, typical values are at Ta = +25C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX | UNITS Input Voltage Range MAX735 4.0 6.2 Vv MAX755 (Note 1) 27 9.0 OmA < ILoAD < 200MA, Ta = O'C to +70C, -40C to +85C (MAX735) |-5.25 -5.0 -4.75 Output Voltage V+ = 4.5V to 6.2V Ta = OC to +70C (MAX755) Vv OmA < ILQAD < 175mA, Ta = -55C to +125C (MAX735) 5.25 -5.0 -4.75 Ta = -40C to +85C, -55C to +125C (MAX755 Ta = OC to +70C, -40C to +85C (MAX735)| 200 275 V4 =4.5V to 6.2V Ta=0 Cto +70C (MAX755) Output Current Thr aOC 10 BSC, SEC tos 126'C (waxes) | 178 mA V+ = 4.0V, VouT = -6V 175 V+ =2.7V, Vout = -5V, MAX755 only 125 Line Regulation V+ = 4.0V to 6.2V 0.1 %N Load Regulation ILOAD = OMA to 200MA 0.001 %imMA Efficiency LOAD = 100mA T 78 % Includes switch MAX735 16 3.0 Supply Current current MAX755 18.35 mA Standby Current V SHDN = OV 10 100 | pA Short-Circuit Current 1.5 A Undervoltage Lock-Out MAX735 only 3.7 4.0 Vv LX On Resistance 0.5 Q LX Leakage Current Vps = 10V 1 _ pA Reference Voltage Ta = +25C (Note 3) 1.15 1.23 1.30 Vv Reference Drift Ta = TmIN to TMAX 50 ppm/C Oscillator Frequency 160 kHz Compensation Pin Impedance 7500 Q SHDN Input Current 1 pA SHDN Logie High 2.0 Vv SHDN Logic Low 0.25 Vv Note 1: Additionaly, Vin is limited to: Vin < 11.7V - IVouTl Note 2: MAX755 external feedback resister tolerance is 0.1%. Note 3: Tested at IVREF = OUA for the MAX735, IvREF = 125uA for the MAX755. a- MAXI-5V/Adjustable, Negative-Output, Inverting, Current-Mode PWM Regulators 150 148 -60 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C) MIAXKISVI 200 0 100 300 SOFT-START VOLTAGE (mV) 500 700 900 65 LOAD CURRENT vs. LOAD CURRENT vs. SUPPLY VOLTAGE SUPPLY VOLTAGE (MAX755) 350 T-7 600 - Ta= 425C CIRCUIT OF FIG. 1 500 _ x0 LS _ = | E 400 / & 5 = 250 ZA = 300 = 8 YH S Ta=+25'C 2 = 200 CIRCUIT OF FIG.1 = | S = WITH R3 = 10k/1%, 200 R4 = 16.2k62/1% 100 Vout = -2V _ s 4 | | | | 35 40 45 50 55 60 65 Oo 12 3 4 5 6 7 8 9 SUPPLY VOLTAGE (V) SUPPLY VOLTAGE (V) PEAK INDUCTOR CURRENT vs. SWITCH ON RESISTANCE vs. LOAD CURRENT 054 SUPPLY VOLTAGE 053 Ta=425C =z = 425C Vout = -5V OF FIG. 1 052 = G@ ost = 3 050 B z 2. Ss B s 2 04g 3 & 2 = 048 z Ss 3 0.47 0.46 0.45 0 50 100 150 200 250 300 40 45 50 55 60 LOAD CURRENT (mA) SUPPLY VOLTAGE (V) OSCILLATOR FREQUENCY vs. SWITCH-CURRENT LIMIT vs. TEMPERATURE & SUPPLY VOLTAGE 1800 SOFT-START VOLTAGE 184 162 1600 | Ta = 425C fe F 60 = 1400 > Vin=+5V | Vin=+4V ~ 4200 Zz (158 = x = 1000 & 156 z = 800 e 154 Sew 3 152 Vin = 46V = 400 1100 Typical Operating Characteristics EFFICIENCY (%) NO-LOAD SUPPLY CURRENT (mA) START-UP DELAY TIME (ms) EFFICIENCY vs. > LOAD CURRENT Se 80 18 VIN = +6V J 76 W 74 n Vin = 45 Qi 70 = ea > 66 >< 64 AS 62 CIRCUIT OF FIG. 1 o 60 QO 0 50 100 150 200 250 300 LOAD CURRENT (mA) NO-LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE (MAX735) 2.0 18 16 Ta=+25C 14 12 1.0 0.8 0.6 0.4 02 0 1.0 2.0 3.0 40 5.0 6.0 SUPPLY VOLTAGE (V) SOFT-START DELAY TIME ILoap = 100mA 69 [CIRCUIT OF FIG. 1 Ta= 425C 50 40 30 20 10 0 0 200 400 600 SOFT-START CAPACITANCE (nF) 800 1000 1200 1400MAX735/MAX755 -5V/Adjustable, Negative-Output, inverting, Current-Mode PWM Regulators Typical Operating Characteristics (continued) A= SWITCH VOLTAGE (LX), 5V/div A=LOAD CURRENT, OmA TO 200mA B=INDUCTOR CURRENT, 500mA/div B= OUTPUT VOLTAGE, 50mV/div C = OUTPUT VOLTAGE RIPPLE, 50mV/div TIMEBASE = 10ms/div TIMEBASE = 2us/div CIRCUIT OF FIG. 1 CIRCUIT OF FIG. 1 VIN =5V_ Vin = SV Ta=+25C Ta=+25C LINE-TRANSIENT RESPONSE A= INPUT VOLTAGE, 4V TO 6V B= OUTPUT VOLTAGE, 50mV/div TIMEBASE = 500us/div CIRCUIT OF FIG. 1 ILOAD = 100MA Ta=425C Pin Description PIN NAME FUNCTION 1 SHDN | SHUTDOWN Control. V+ = normal operation, GND = shutdown. 2 VREF | Reference Voltage Output = 1.23V. Supplies up to 125,1A for external loads. 3 Ss Soft-Start 4 cc Compensation Input of the error amplifier and feedback summing node. 5 Vout Cuput voltage feedback terminal (actually an input); connected to internal resistors (MAX735). Also provides river bias. 6 GND Ground 7 LX Switch Output - internal P-channel MOSFET drain 8 V4 Positive Supply-Voltage Input. Bypass with a 1,.F ceramic capacitor close to V+ and GND pins. Use additional bypass capacitor as shown in Figures 1, 2, and 3. DAKIAVL-5V/Adjustable, Negative-Output, Inverting, Current-Mode PWM Regulators = i 8 SHON V+ apg; eur MAXLM = IB a wae | A7urNOV Mm VREF X CAAA a 1N5817 8 Rt SS GND F-_ 10.0k 57 sv cc Your oy ovreur #L 100pF OV WW, = (00H Ra" 40.7k OPTIONAL LOWPASS OUTPUT FILTER FILTER OUTPUT 25nH f. .. OUTPUT T 22uF * MAY BE OMITTED IF LOAD CURRENT IS LIMITED TO 100mA **MAX755 ONLY 40vT0 SHON Vt oH wPUT 3 470uF/6V = ALUMINUM ELECTROLYTIC . RAS = Ber aa OPTIONAL LOWPASS OUTPUT FILTER FILTER OUTPUT 25H... OUTPUT +L 22uF * MAY BE OMITTED IF LOAD CURRENT IS LIMITED TO 100mA **MAX755 ONLY Figure 1. Application Circuit Using Surface-Mount Components (Commercial and Extended Industrial Temperature Ranges) 4.0VT0 = 8 6.2V SHDN V+ ar a INPUT MAXIAA wos Ms |r qu Ot VREF UX ut ; & 1nsi7 Rg*** SS GND }_ 40.0k = 5 -5.0V cc Vout Toy oureur #L 220ur MOV WN = 0S-CON** Rave 40.7k : OPTIONAL LOWPASS OUTPUT FILTER FILTER OUTPUT 25pH p> ,. OUTPUT 22uF ae * MAY BE OMITTED IF LOAD CURRENT 1S LIMITED TO 100mA = QS-CON CAPACITORS LIMITED 10 -55C TO +105C OPERATION. OR OFERATON UP TO +125C, OTHER CAPACITORS MUST BE SPECIFIED. ***MAX7955 ONL . Figure 3. Application Circuit Using Through-Hole Components (All Temperature Ranges) MIAKIsvI ute 2. Application Circuit Using Through-Hole Components (Commercial Temperature Range Detailed Description Operating Principle The MAX735/MAX755 are monolithic CMOS ICs contain- ing a current-mode PWM controller and a 2A P-channel power MOSFET. Current-mode control provides excel- lent line-transient response, inherent overcurrent protec- tion, and excellent AC stability. The switch transistor is a current-sensing MOSFET that splits off a fraction of the total source current for current-limit detection. Basic Application Circuits The three basic application circuits shown are simple designs using standard, off-the-shelf components. Fig- ure 1s circuit uses tantalum surface-mount capacitors and a surface-mount inductor, minimizing board space and allowing for wide-temperature operation. The low equivalent series resistance (ESR) of the tantalum capacitors (typically 7OmQ at +25C and 140mQ at -55C) makes for a quiet output (see Switching Wave- forms in the Typical Operating Characteristics). SSLXVW/SEZLXUINMAX735/MAX755 -5V/Adjustable, Negative-Output, inverting, Current-Mode PWM Regulators VIN +4V706.2V 10uF tt C1 i our 150uF SHON Ve OVERCURRENT COMPARATOR BIAS SLOPE tl enue | GEN COMPENSATION v 2 - Our RSENSE ese ERROR AMP CURRENT. + a z oc : SENSE AMP 2 Bi " LX ie 82pF* - - agi "> . 1.23 7 a = BANDGAP I UL TO Vout 1 2 VREF - QuH = a7OuF T 160kHz tod 10pF == = AAAXLAA = = wT aM > MAX735 ~ MAX755 $s | SS CLAMP r 1 33M" 1 t I ' LT aw) aa ' uvLo Le~------+------ eee = = = GND *MAY BE OMITTED (F LOAD CURRENT (S LIMITED TO 100mA. **MAXT35 ONLY ***MMAXTS5 ONLY Figure 4. Detailed Block Diagram Figure 2's circuit provides a through-hole solution for commercial-temperature operation. The capacitors are radial-lead aluminum electrolytics with an ESR of approx- imately 100mQ at +25C. These and other standard aluminum electrolytic capacitors have an ESR 100 times greater at -55C than at +25C, so they are not recom- mended for operation below 0C. Since output voltage ripple is proportional to the ESR of the output filter capac- itor, the ripple with standard aluminum electrolytic capac- itors is 1.4 times that associated with tantalum capacitors. Refer to Figure 3 for a wide-temperature, through-hole solution. The capacitors are organic semiconductor (Os-Con) alurninum electrolytics, which exhibit low ESR over a wide temperature range (typically 30mQ at +25C and -55C). Table 1 lists component suppliers for the circuits dis- cussed above. If the load current is limited to 100mA, R1, R2, and C3 (Figures 1-3) may be omitted. The 1.0uF V+ bypass capacitor must he placed as close as possible to pins 6 and 8. Output-Ripple Filtering An optional lowpass pi-filter (Figures 1-3) can be added to the output to reduce output ripple to about S5mVp-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 volt- age drop. Note that the feedback must be taken before the filter, not after the filter. MAKI-5V/Adjustable, Negative-Output, inverting, Current-Mode PWM Regulators Soft-Start Buffer The voltage applied to the Soft-Start (SS) input de- termines the peak switch-current limit (see Soft-Start Delay Time graph in Typical Operating Characteris- tics). A capacitor attached to SS ensures an orderly power-up sequence by gradually increasing the cur- rent limit. SS is pulled up to VREF internally through a 1.2MQ resistor. The maximum current limit can be fixed externally at a lower than normal value by clamping the SS voltage to a voltage less than VREF. An SS cycle is initiated whenever either an undervolt- age lockout (MAX735 only) or overcurrent fault con- dition triggers an internal transistor to discharge the SS capacitor to ground. Note that the SS capacitor should be at least 10nF for the overcurrent limit to function properly. Undervoitage Lockout The MAX735 operates for supply voltages greater than 3.7V typ (4V guaranteed), with 0.25V of hysteresis. inter- nal control logic holds the output power MOSFET off until the supply rises above the undervoltage threshold, at which time a soft-start cycle begins. The MAX755 operates with supply voltages greater than +2.7V. It does not have the undervoitage lockout feature of the MAX735. The output is limited to [VouTI $< 11.7V - VIN. inductor Selection The MAX735 and MAX755 operate with a standard 10H inductor for the entire range of supply voltages and load currents. The inductor must have a saturation (incremen- tal) current rating greater than the peak switch current obtained from the Peak Inductor Current vs. Load Current graph under Typical Operating Characteristics. Output Adjustment - MAX755 The output voltage for the MAX755 is set by two resistors, R3 and R4, which form a voltage divider between the output, CC pin, and VREF pin. The regulator adjusts the output voltage so the voltage at CC is GND. R3 can be any value from 10kQ to 20kQ. R4 is given by the following formula: _ Vout! ~ 1.23 The output is limited to IVouTI s 11.7V - VIN. R4 R3 MAXI AVI Table 1. Component Suppliers PRODUCTION METHOD INDUCTORS CAPACITORS Sumida Matsuo Surface Mount | 54-100 (10uH) | 267 series Sanyo Miniature Sumida Os-Con series Through Hole | RCH855-100M (10HH)|! low-ESR organic semiconductor Nichicon ft seres Low-Cost Renco jow-ESR Through Hole | RL 1284 (10pH) electrolytics United Chemicon LXF series Matsuo USA (714) 969-2491 FAX (714) 960-6492 Matsuo Japan (06) 332-0871 Nichicon (708) 843-7500 FAX (708) 843-2798 Renco (516) 586-5566 FAX (516) 586-5562 Sanyo Os-Con USA (619) 661-6322 Sanyo Os-Con Japan (0720) 70-1005 FAX (0720) 70-1174 Sumida USA (708) 956-0666 Sumida Japan (03) 3607-5111 FAX (03) 3607-5428 United Chemi-Con (708) 696-2000 FAX (708) 640-6311 Printed Circuit Layout and Grounding Good layout and grounding practices will ensure low- noise, jitter-free operation. Minimize wire lengths in the high-current paths, especially the distance between the inductor and the return leads of the filter and bypass capacitors (Ct and C2). These high-current ground connections should be brought to a single common point (a "star" ground). Place a low-ESR bypass capacitor directly at V+ and GND. The use of sockets or wire-wrap boards is not recommended. SSZXVW/SELXVINMAX735/MAX755 -5V/Adjustable, Negative-Output, Inverting, Current-Mode PWM Regulators Chip Topography MAX735/MAX755 0.116" (2.946 mm) 0.072" {1.828 mm) Note: TRANSISTOR COUNT: 274 CONNECT SUBSTRATE TO V+ 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. 8 Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 1994 Maxim Integrated Products Printed USA MAXIAA js a registered trademark of Maxim Integrated Products.