LTC1876 High Efficiency, 2-Phase, Dual Synchronous Step-Down Switching Controller and Step-Up Regulator FEATURES DESCRIPTIO Step-Down Controller The LTC 1876 is a high performance triple output switching n regulator. It incorporates a dual step-down switching con- Out-of-Phase Controllers Reduce Required Input Capacitance and Power Supply Induced Noise troller that drives all N-channel synchronous power MOSFET n stages. A step-up regulator with an internal 1A, 36V switch Power Good Output Voltage Indicator TM provides the third output. n OPTI-LOOP Compensation Minimizes C OUT n DC Programmed Fixed Frequency 150kHz to 300kHz The step-down controllers minimize power loss and noise n Wide V Range: 3.5V to 36V Operation IN by operating the output stage of each controller out of n Very Low Dropout Operation: 99% Duty Cycle phase. OPTI-LOOP compensation allows the transient n Adjustable Soft-Start Current Ramping response to be optimized over a wide range of output n Latched Short-Circuit Shutdown with Defeat Option capacitance and ESR values. A RUN/SS pin for each n Remote Output Voltage Sense and OV Protection controller provides both soft-start and an optional timed, n 5V and 3.3V Standby Regulators short-circuit shutdown that can be configured to latch off TM n Selectable Const. Freq. or Burst Mode Operation one or both controllers. Current foldback provides additional short-circuit protection. In an overvoltage Step-Up Regulator n High Operating Switching Frequency of 1.2MHz condition, the bottom MOSFET is latched on until V OUT n returns to normal. The FCB pin can be used to inhibit Burst Low Internal V Switch: 400mV 1A, V = 3V CESAT IN Mode operation or to enable regulation of a secondary n Wide V Range: 2.6V to 16V Operation IN output voltage. n High Output Voltage: Up to 34V U The step-up regulator operates at 1.2MHz, allowing the APPLICATIO S use of tiny low cost capacitors and inductors. In addition, n its internal 1A switch allows high current outputs to be 3.3V Input Step-Down Converter n generated. Its current mode control scheme provides Notebook and Palmtop Computers, PDAs excellent line and load regulation. n Battery-Operated Digital Devices , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode and OPTI-LOOP are trademarks of Linear Technology Corporation. TYPICAL APPLICATIO 10H V IN 5.2V 33F 10F TO 28V V 35V 1F OUT3 35V 4.7F 12V ALUM CER CER 10V INTV AUXV V CC IN IN 200mA M3 M1 TG2 TG1 10F 20V 0.1F 0.1F BOOST2 BOOST1 6.3H SW2 SW1 6.8H LTC1876 M4 M2 BG2 BG1 AUXSW PGND AUXV FB PGOOD AUXSD 86.6k, 1% + + SENSE2 SENSE1 0.01 1000pF 1000pF 0.01 V SENSE2 SENSE1 OUT1 V OUT2 5V 3.3V V V OSENSE2 OSENSE1 4A 5A 63.4k 105k I I TH2 TH1 1% 1% + 56F 47F 220pF RUN/SS2 SGND RUN/SS1 220pF 4V 6.3V 20k 10.2k 20k SP SP 1% 1% 1% 15k 0.1F 0.1F 15k M1, M2, M3, M4: FDS6680A 1876 TA01 Figure 1. High Efficiency Triple 5V/3.3V/12V Power Supply 1876fa 1 + + + + U ULTC1876 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) Input Supply Voltage (V )......................... 36V to 0.3V ORDER PART IN TOP VIEW Topside Driver Voltages NUMBER RUN/SS1 1 36 PGOOD (BOOST1, BOOST2) ................................... 42V to 0.3V + SENSE1 2 35 TG1 LTC1876EG Switch Voltage (SW1, SW2) ......................... 36V to 5V SENSE1 3 34 SW1 V 4 33 BOOST1 OSENSE1 INTV EXTV , RUN/SS1, RUN/SS2, PGOOD, CC, CC FREQSET 5 32 V IN (BOOST1-SW1), (BOOST2-SW2), ...............7V to 0.3V STBYMD 6 31 BG1 + + SENSE1 , SENSE2 , SENSE1 , SENSE2 FCB 7 30 EXTV CC Voltages ................................... (1.1)INTV to 0.3V I 8 29 INTV TH1 CC CC 9 28 PGND SGND FREQSET, STBYMD, FCB, PGOOD 10 27 BG2 3.3V OUT Voltages ..................................................7V to 0.3V I 11 26 BOOST2 ITH2 I I , V , V Voltages ... 2.7V to 0.3V TH1, TH2 OSENSE1 OSENSE2 V 12 25 SW2 OSENSE2 SENSE2 13 24 TG2 Peak Output Current <10m s (TG1, TG2, BG1, BG2) ... 3A + SENSE2 14 23 RUN/SS2 INTV Peak Output Current ................................ 50mA CC AUXSGND 15 22 AUXSD AUXV .................................................................. 16V to 0.3V IN AUXV 16 21 AUXV FB IN AUXSD..................................................................... 10V AUXSW 17 20 AUXPGND AUXSW 18 19 AUXPGND AUXSW ..................................................... 36V to 0.3V AUXV Voltage ....................................... 2.5V to 0.3V G PACKAGE FB 36-LEAD PLASTIC SSOP Current into AUXV ....................................................... 1mA FB T = 125 C, q = 95 C/W JMAX JA Operating Temperature Range (Note 2) ...40 C to 85 C Junction Temperature (Note 3)............................. 125 C Consult factory for parts specified with wider operating temperature ranges. Storage Temperature Range ..................65 C to 150 C Lead Temperature (Soldering, 10 sec).................. 300 C ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25 C. V = 15V, V = 5V, AUXV = 3V unless otherwise noted. A IN RUN/SS1, 2 IN SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Main Control Loops V Regulated Feedback Voltage I Voltage = 1.2V (Note 4) l 0.792 0.800 0.808 V OSENSE1, 2 TH1, 2 I Feedback Current (Note 4) 5 50 nA VOSENSE1, 2 V Reference Voltage Line Regulation V = 3.6V to 30V (Note 4) 0.002 0.02 %/V REFLNREG IN V Output Voltage Load Regulation (Note 4) LOADREG Measured in Servo Loop D I Voltage = 1.2V to 0.7V l 0.1 0.5 % TH Measured in Servo Loop D I Voltage = 1.2V to 2V l 0.1 0.5 % TH g Transconductance Amplifier g I = 1.2V Sink/Source 5m A (Note 4) 1.3 mmho m1, 2 m TH1, 2 g Transconductance Amplifier GBW I = 1.2V (Note 4) 3 MHz mOL1, 2 TH1, 2 I Input DC Supply Current (Note 5) Q Normal Mode V = 15V EXTV Tied to V V = 5V 350 m A IN CC OUT1 OUT1 Standby V = 0V, V > 2V 125 m A RUN/SS1, 2 STBYMD Shutdown V = 0V, V = Open 20 35 m A RUN/SS1, 2 STBYMD V Forced Continuous Threshold l 0.76 0.800 0.84 V FCB I Forced Continuous Current V = 0.85V 0.3 0.18 0.1 m A FCB FCB V Burst Inhibit (Constant Frequency) Measured at FCB pin 4.3 4.8 V BINHIBIT Threshold 1876fa 2 U WWW