LTC3711 5-Bit Adjustable, Wide Operating Range, TM No R Step-Down Controller SENSE DESCRIPTIO FEATURES n 5-Bit Programmable Output Voltage: 0.925V to 2V The LTC 3711 is a synchronous step-down switching n No Sense Resistor Required regulator controller for CPU power. An output voltage n True Current Mode Control between 0.925V and 2.000V is selected by a 5-bit code n 2% to 90% Duty Cycle at 200kHz (Intel mobile VID specification). The controller uses a n t < 100ns valley current control architecture to deliver very low duty ON(MIN) n Supports Active Voltage Positioning cycles without requiring a sense resistor. Operating fre- n Extremely Fast Transient Response quency is selected by an external resistor and is compen- n Stable with Ceramic C sated for variations in V and V . OUT IN OUT n Dual N-Channel MOSFET Synchronous Drive Discontinuous mode operation provides high efficiency n Power Good Output Voltage Monitor operation at light loads. A forced continuous control pin n Wide V Range: 4V to 36V IN reduces noise and RF interference and can assist second- n 1% 0.8V Reference ary winding regulation by disabling discontinuous mode n Adjustable Current Limit operation when the main output is lightly loaded. n Adjustable Switching Frequency n Fault protection is provided by internal foldback current Programmable Soft-Start n limiting, an output overvoltage comparator and optional Output Overvoltage Protection n short-circuit shutdown timer. Soft-start capability for sup- Optional Short-Circuit Shutdown Timer n ply sequencing is accomplished using an external timing Micropower Shutdown: I < 30m A Q n capacitor. The regulator current limit level is user pro- Available in 24-Lead Narrow SSOP Package grammable. Wide supply range allows operation from 4V U to 36V at the input. APPLICATIO S , LTC and LT are registered trademarks of Linear Technology Corporation. n No R is a trademark of Linear Technology Corporation. Power Supplies for Mobile Pentium Processors SENSE Pentium is a registered trademark of Intel Corporation. n Notebook and Palmtop Computers, PDAs TYPICAL APPLICATIO R ON 330k Efficiency vs Load Current PGOOD I ON 100 C SS V V = 1.5V IN OUT 0.1F V IN 5V TO 24V EXTV = 5V C CC IN M1 V = 5V IN RUN/SS TG 22F IRF7811A L1 C 500pF 50V 90 C 1H I SW V TH 3 OUT R 20k 1.5V C 0.33F C B V = 15V IN C SGND BOOST 15A OUT + D B 270F 80 LTC3711 CMDSH-3 2V INTV 4 CC M2 D1 VID4 BG IRF7811A C : UNITED CHEMICON UPS840 IN + 2 70 THCR70EIH226ZT VID3 C VCC 4.7F C : CORNELL DUBILIER OUT 5-BIT VID VID2 PGND ESRE271M02B VID1 L1: SUMIDA CEP125-IROMC 3711 F01a VID0 V 60 OSENSE 0.01 1 10 0.1 LOAD CURRENT (A) 3711 F01b Figure 1. High Efficiency Step-Down Converter 3711f 1 EFFICIENCY (%) U ULTC3711 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART TOP VIEW Input Supply Voltage NUMBER V , I ..................................................36V to 0.3V VID2 1 24 VID1 IN ON Boosted Topside Driver Supply Voltage RUN/SS 2 23 VID0 LTC3711EGN V 3 22 BOOST BOOST.................................................. 42V to 0.3V ON + PGOOD 4 21 TG SW, SENSE Voltages ................................. 36V to 5V V 5 20 SW RNG EXTV , (BOOST SW), RUN/SS, CC + FCB 6 19 SENSE VID0-VID4, PGOOD Voltages ..................... 7V to 0.3V I 7 18 PGND TH FCB, V , V Voltages .......... INTV + 0.3V to 0.3V ON RNG CC SGND 8 17 BG I , V , V Voltages....................... 2.7V to 0.3V TH FB OSENSE I 9 16 INTV CC ON TG, BG, INTV , EXTV Peak Currents.................... 2A CC CC V 10 15 V IN FB TG, BG, INTV , EXTV RMS Currents .............. 50mA CC CC V 11 14 EXTV CC OSENSE Operating Ambient Temperature Range VID3 12 13 VID4 LTC3711EGN (Note 2) ........................ 40 C to 85 C GN PACKAGE Junction Temperature (Note 3)............................ 125 C 24-LEAD PLASTIC SSOP Storage Temperature Range ................. 65 C to 150 C T = 125 C, q = 130 C/ W JMAX JA Lead Temperature (Soldering, 10 sec).................. 300 C Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T = 25 C. V = 15V unless otherwise noted. A IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loop I Input DC Supply Current Q Normal 900 2000 m A Shutdown Supply Current 15 30 m A V Feedback Reference Voltage I = 1.2V (Note 4) l 0.792 0.800 0.808 V FB TH D V Feedback Voltage Line Regulation V = 4V to 30V, I = 1.2V (Note 4) 0.002 %/V FB(LINEREG) IN TH D V Feedback Voltage Load Regulation I = 0.5V to 1.9V (Note 4) l 0.05 0.3 % FB(LOADREG) TH I Feedback Input Current V = 0.8V 5 50 nA FB FB g Error Amplifier Transconductance I = 1.2V (Note 4) l 1.4 1.7 2 mS m(EA) TH V Forced Continuous Threshold l 0.76 0.8 0.84 V FCB I Forced Continuous Pin Current V = 0.8V 1 2 m A FCB FCB t On-Time I = 60m A, V = 1.5V 212 250 288 ns ON ON ON I = 30m A, V = 1.5V 425 500 575 ns ON ON t Minimum On-Time I = 180m A, V = 0V 50 100 ns ON(MIN) ON ON t Minimum Off-Time I = 60m A, V = 1.5V 250 400 ns OFF(MIN) ON ON V Maximum Current Sense Threshold V = 1V, V = 0.76V 113 133 153 mV SENSE(MAX) RNG FB + V V V = 0V, V = 0.76V l 79 93 107 mV PGND SENSE RNG FB V = INTV , V = 0.76V 158 186 214 mV RNG CC FB V Minimum Current Sense Threshold V = 1V, V = 0.84V 67 mV SENSE(MIN) RNG FB + V V V = 0V, V = 0.84V 47 mV PGND SENSE RNG FB V = INTV , V = 0.84V 93 mV RNG CC FB D V Output Overvoltage Fault Threshold 5.5 7.5 9.5 % FB(OV) V Output Undervoltage Fault Threshold 520 600 680 mV FB(UV) 3711f 2 U WWW