LTC7821 Hybrid Step-Down Synchronous Controller FEATURES DESCRIPTION n Wide V Range: 10V to 72V (80V ABS Max) The LTC 7821 uses a proprietary architecture that merges IN n Soft Switching for Low Noise Operation a soft switching charge pump topology with a synchro- n nous step-down converter to provide superior efficiency Phase-Lockable Fixed Frequency 200kHz to 1.5MHz n and EMI performance compared to traditional switching 1% Output Voltage Accuracy n architectures. R or DCR Current Sensing SENSE n Programmable CCM, DCM, or Burst Mode Operation In a typical 48V to 12V application, efficiency of greater n CLKOUT Pin for Multiphase Operation than 97% is attainable with the LTC7821 switching at n Short Circuit Protected 500kHz. The same efficiency can only be achieved with a n EXTV Input for Improved Efficiency CC traditional controller switching at one-third the frequency. n Monotonic Output Voltage Start-Up Higher switching frequencies allow the use of smaller in- n Optional External Reference ductances that yield faster transient response and smaller n 32-Pin (5mm 5mm) QFN solution size. The LTC7821 can be easily paralleled to provide higher APPLICATIONS output currents with its accurate current sharing capability n Intermediate Bus Converters and frequency synchronization function. n High Current Distributed Power Systems All registered trademarks and trademarks are the property of their respective owners. Protected n Telecom, Datacom, and Storage Systems by U.S. patents, Including 9484799. n Automotive Applications TYPICAL APPLICATION Efficiency at Various V for 100 IN V IN V = 12V OUT 1F 36V TO 72V + 2.2F 100 C IN V V IN SENSE IN 6 100F TG1 M1 99 CB1, 0.22F I = 10A OUT BOOST1 98 SW1 I = 20A OUT TIMER D1 97 LTC7821 M2 BG1 96 C FLY FREQ 10F BOOST2 CB2 8 95 0.47F MID f = 500KHz SW 94 MID SENSE V = 12V INTV EXT REF OUT CC D2 C MID 1k CCM 10F 10k 10k 0.1F 93 8 30 40 50 60 70 80 M3 TG2 FAULT FAULT INPUT VOLTAGE (V) 7821 TA01b PGOOD PGOOD BOOST3 CB3 2H 1F V D3 OUT PINS NOT SHOWN IN THIS CIRCUIT: 12V SW3 CLKOUT I TH 20A INTV CC TEMP 0.22F 10F M4 6.81k RUN BG2 2 HYS PRGM 4.7F + C OUT MODE/PLLIN INTV CC 150F TRACK/SS 2 PGND 8V EXTV CC + I 4.32k SNS V FB I M1: BSZ070N08LSS SNS M2, M3: BSC032N04LS 60.4k 7821 TA01a M4: BSC014N04LSI Rev A 1 Document Feedback For more information www.analog.com EFFICIENCY (%)LTC7821 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW Input Supply Voltage (V , V ) ....... 0.3V to 80V IN IN SENSE Top Side Driver Voltages BOOST1 ................................................. 0.3V to 86V 32 31 30 29 28 27 26 25 BOOST2, BOOST3.................................. 0.3V to 46V MODE/PLLIN 1 24 BG1 Switch Voltages CLKOUT 2 23 BOOST2 SW1 ............................................................ 0V to 80V RUN 3 22 BOOST3 FAULT 4 21 TG2 SW3 ....................................................... 0.3V to 40V 33 PGOOD 5 SGND 20 SW3 MID, MID SENSE ....................................... 0.3V to 40V TIMER 6 19 INTV CC (BOOST1-SW1), (BOOST2-MID), TRACK/SS 7 18 BG2 (BOOST3-SW3) ............................................ 0.3V to 6V EXT REF 8 17 PGND + I , I ................................................ 0.3V to 40V SNS SNS 9 10 11 12 13 14 15 16 + (I I ) .......................................................0.6V SNS SNS EXTV ...................................................... 0.3V to 40V CC TEMP, FREQ, EXT REF, V ..................0.3V to INTV FB CC UH PACKAGE HYS PRGM, I , RUN, TRACK/SS .......0.3V to INTV TH CC 32-LEAD (5mm 5mm) PLASTIC QFN T = 125C, = 44C/W, = 7.3C/W FAULT, PGOOD ........................................... 0.3V to 80V JMAX JA JC EXPOSED PAD (PIN 33) IS GND, MUST BE SOLDERED TO PCB TIMER, MODE/PLLIN ............................0.3V to INTV CC INTV Peak Output Current ................................100mA CC Operating Junction Temperature Range (Notes 2, 3, 9) .................................... 40C to 125C Storage Temperature Range .................. 65C to 150C ORDER INFORMATION