LTC1873 Dual 550kHz Synchronous 2-Phase Switching Regulator Controller with 5-Bit VID FEATURES DESCRIPTIO n Two Independent PWM Controllers in One Package The LTC 1873 is a dual switching regulator controller opti- n Side 1 Output Is Compliant with Intel Desktop mized for high efficiency with low input voltages. It includes VRM 8.4 Specifications (Includes 5-Bit VID DAC) two complete, on-chip, independent switching regulator con- n 1.3V to 3.5V Output Voltage with 50mV/100mV Steps trollers. Each is designed to drive a pair of external n Two Sides Run Out-of-Phase to Minimize C N-channel MOSFETs in a voltage mode feedback, synchro- IN n All N-Channel External MOSFET Architecture nous buck configuration. The LTC1873 includes digital out- n No External Current Sense Resistors Required put voltage adjustment on side 1 that conforms to the Intel n Precison Internal 0.8V 1% Reference Desktop VID specification. A constant-frequency, true PWM n 550kHz Switching Frequency Minimizes External design minimizes external component size and cost and Component Size optimizes load transient performance. The synchronous buck n Very Fast Transient Response architecture automatically shifts to discontinuous and then to TM n Up to 25A Output Current per Channel Burst Mode operation as the output load decreases, ensur- n Low Shutdown Current: < 100m A ing maximum efficiency over a wide range of load currents. n Small 28-Pin SSOP Package The LTC1873 features an onboard reference trimmed to 1% and delivers better than 1.5% regulation at the converter U outputs over all combinations of line, load and temperature. APPLICATIO S Each channel can be enabled independently with both chan- n Microprocessor Core and I/O Supplies nels disabled, the LTC1873 shuts down and supply current n Multiple Logic Supply Generator drops below 100m A. n High Efficiency Power Conversion , LTC and LT are registered trademarks of Linear Technology Corporation. n Chipset Power Supply Burst Mode is a trademark of Linear Technology Corporation. TYPICAL APPLICATIO Low Cost Desktop CPU Supply with RDRAM Keepalive IN OUT 4.5V TO 5.5V + 1F LT1761 10 C IN 16.2k 0.1% GND ADJ + MBR0530T 4.75k 10F 10k 0.1% V PV CC CC 0.1% 16.9k FB2 BOOST2 330pF 0.1% 56pF 68k QT2 1F TG2 L2 V COMP2 RDRAM SW2 2.5V/7A + 2.45V/100mA STANDBY RUN/SS2 BG2 QB2 1k C OUT2 47k RUN/SS1 QSS1 I 0.1F MAX2 STBY/ON QSS2 1k FAULT LTC1873 MBR0530T BOOST1 SENSE 1F QT1B FB1 220pF TG1 QT1A L1 39pF 56k V CORE COMP1 SW1 1.3V TO 3.5V 20A + BG1 QB1A FCB C OUT1 C = SANYO 10MV1200GX (6 IN PARALLEL) IN QB1B C = SANYO 6MV1500GX (8 IN PARALLEL) OUT1 33k 5-BIT VID VID4:0 I C = SANYO 6MV1500GX (3 IN PARALLEL) MAX1 OUT2 L1: 1H SUMIDA CEP125-1R0MC-H SGND PGND L2: 2.2H COILTRONICS UP2B-2R2 QSS1, QSS2: MOTOROLA MMBT3904LT1 QT1A, QT1B, QB1A, QB1B: FAIRCHILD FDS6670A 1873 TA01 QT2, QB2: 1/2 SILICONIX Si4966 1 U ULTC1873 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW ORDER PART Supply Voltage NUMBER PV 1 28 I MAX2 CC V ........................................................................................... 7V CC BOOST1 2 27 BOOST2 BOOSTn............................................................... 15V LTC1873EG BG1 3 26 BG2 TG1 4 25 TG2 BOOSTn SWn .................................................... 7V SW1 5 24 SW2 Input Voltage I 6 23 PGND MAX1 SWn .......................................................... 1V to 8V FCB 7 22 FAULT VIDn ....................................................... 0.3V to 7V RUN/SS1 8 21 RUN/SS2 COMP1 9 20 COMP2 All Other Inputs ......................... 0.3V to V + 0.3V CC SGND 10 19 FB2 Peak Output Current < 10m s FB1 11 18 V CC TGn, BGn ............................................................... 5A SENSE 12 17 VID4 Operating Temperature Range VID0 13 16 VID3 VID1 14 15 VID2 (Note 2) ............................................. 40 C to 85 C Storage Temperature Range ................. 65 C to 150 C G PACKAGE 28-LEAD PLASTIC SSOP Lead Temperature (Soldering, 10 sec).................. 300 C T = 125 C, q = 55 C/ W JMAX JA Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS The l denotes specifications which apply over the full operating temperature range, otherwise specifications are T = 25 C. A V = 5V unless otherwise specified. (Note 4) CC SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loop V V Supply Voltage l37 V CC CC PV PV Supply Voltage (Note 3) l37 V CC CC BV BOOST Pin Voltage V V (Note 3) l 2.7 7 V CC BOOST SW I V Supply Current Test Circuit 1 l 2.2 8 mA CC CC RUN/SS1 = RUN/SS2 = 0V (Note 6) l 30 100 m A IPV PV Supply Current Test Circuit 1 (Note 5) l 2.2 6 mA CC CC RUN/SS1 = RUN/SS2 = 0V (Note 6) l 6 100 m A I BOOST Pin Current Test Circuit 1 (Note 5) l 1.3 3 mA BOOST RUN/SS1 = RUN/SS2 = 0V l 0.1 10 m A V Feedback Voltage Test Circuit 1 l 0.790 0.800 0.810 V FB D V Feedback Voltage Line Regulation V = 3V to 7V l 0.005 0.05 %/V FB CC I Feedback Current FB2 Only (Note 7) l 0.001 1 m A FB V FCB Threshold l 0.75 0.8 0.85 V FCB D V FCB Feedback Hysteresis 20 mV FCB I FCB Pin Current l 0.001 1 m A FCB V RUN/SS Pin RUN Threshold l 0.45 0.55 0.65 V RUN I Soft Start Source Current RUN/SSn = 0V 1.5 3.5 5.5 m A SS 2 U WWW