Datasheet LTC7817 (Analog Devices)

LTC7817 40V, Low IQ, 3MHz, Triple Output Buck/Buck/Boost Synchronous Controller
FEATURES DESCRIPTION
n
Dual Buck Plus Single Boost Synchronous Controllers
The LTC®7817 is a high performance triple output (buck/ n
Low Operating I
buck/boost) synchronous DC/DC switching regulator con-
Q: 14μA (14V to 3.3V, Channel 1 On)
troller that drives all N-channel power MOSFET stages. n
Outputs Remain in Regulation Through Cold Crank
Its constant frequency current mode architecture allows a phase-lockable switching frequency of up to 3MHz.
Down to 1V Input Supply Voltage
n The LTC7817 operates from a wide 4.5V to 40V input
Wide Bias Input Voltage Range: 4.5V to 40V
n supply range. When biased from the output of the boost
Buck and Boost Output Voltages up to 40V
n converter or another auxiliary supply, the LTC7817 can
RSENSE or DCR Current Sensing
operate from an input supply as low as 1V after start-up. n
Pass-Thru™ Operation: 100% Duty Cycle for Boost Synchronous MOSFET
The very low no-load quiescent current extends operating n
Programmable Fixed Frequency (100kHz to 3MHz)
run time in battery powered systems. OPTI-LOOP® com- n Phase-Lockable Frequency (100kHz to 3MHz) pensation allows the transient response to be optimized n over a wide range of output capacitance and ESR values. Selectable Continuous, Pulse-Skipping, or Low The LTC7817 features a precision 0.8V reference for the Ripple Burst Mode Operation at Light Loads n bucks, 1.2V reference for the boost and a power good Very Low Buck Dropout Operation: 99% Duty Cycle n output indicator. Low Shutdown IQ: 1.5μA n Small 38-Lead 5mm × 7mm QFN Package The LTC7817 synchronous boost Pass-Thru capability n AEC-Q100 Automotive Qualification in Process minimizes losses in automotive start-stop applications. All registered trademarks and trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 5705919, 5929620, 6144194, 6177787, 6580258.
APPLICATIONS
n Automotive and Transportation n Industrial n Military/Avionics
TYPICAL APPLICATION
VOUT3 REGULATED TO 10V WHEN VIN < 10V FOLLOWS VIN WHEN VIN > 10V 150µF 22µF VBIAS VFB3
LTC7817 Response to a Cold
TG3 TG1
LTC7818 Response to a Cold Crank
BOOST3 BOOST1
Crank Automotive Waveform Automotive Waveform
1.5mΩ 1.4µH 0.1µF 0.1µF 0.9µH 2mΩ VOUT1 VIN SW3 3.3V 1V TO 38V SW1 12A STARTUP 22µF 330µF ABOVE 5V 150µF BG3 BG1 VBATT LTC7817 VOUT3 SENSE3– SENSE1+ 210k SENSE3+ SENSE1– VFB1 VOUT3 RUN1,2,3 VOLTAGE V I OUT3 68.1k 2V/DIV TH1,2,3 TRACK/SS1,2,3 VOUT2 TG2 INTVCC BOOST2 V 4.7µF VPRG3 OUT1 0.1µF 1.8µH 3mΩ VOUT2 5V 0.1µF SW2 10A BG2 10µF 330µF BOOST1,2,3 0V TIME (10ms/DIV) 7817 TA01b SENSE2+ PLLIN/MODE 357k SENSE2– FREQ VFB2 EXTV PGND SGND CC VOUT2 68.1k 7817 TA01a Rev 0 Document Feedback For more information www.analog.com 1 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Typical Application Related Parts