Datasheet LTC7812 (Analog Devices)

LTC7812 Low IQ, 38V Synchronous Boost+Buck Controller
FEATURES DESCRIPTION
n
Synchronous Boost and Buck Controllers
The LTC®7812 is a high performance synchronous n
When Cascaded, Allows VIN Above, Below or Equal
Boost+Buck DC/DC switching regulator controller that
to Regulated VOUT
drives all N-channel power MOSFET stages. It contains n
Output Remains in Regulation Through Input Dips
independent step-up (boost) and step-down (buck) control-
(e.g., Cold Crank) Down to 2.5V
lers that can regulate two separate outputs or be cascaded n
Wide Bias Input Voltage Range: 4.5V to 38V
to regulate an output voltage from an input voltage that n
Low Input and Output Ripple
can be above, below or equal to the output voltage. The n
Low EMI
LTC7812 operates from a wide 4.5V to 38V input supply n
Fast Output Transient Response
range. When biased from the output of the boost regulator, n
High Light Load Efficiency
the LTC7812 can operate from an input supply as low as n
Low Operating I
2.5V after start-up. The 33μA no-load quiescent current
Q: 33µA (Both Channels On)
n
Low Operating I
extends operating run time in battery-powered systems.
Q: 28µA (Buck Channel On)
n
RSENSE or Lossless DCR Current Sensing
Unlike conventional buck-boost regulators, the LTC7812’s n Buck Output Voltage Range: 0.8V ≤ VOUT ≤ 24V cascaded Boost+Buck solution has continuous, non- n Boost Output Voltage Up to 60V pulsating, input and output currents, substantially reducing n Phase-Lockable Frequency (75kHz to 850kHz) voltage ripple and EMI. The LTC7812 has independent n Small 32-Pin 5mm × 5mm QFN Package feedback and compensation points for the boost and buck regulation loops, enabling a fast output transient response
APPLICATIONS
that can be easily optimized externally. n Automotive and Industrial Power Systems L, LT, LTC, LTM, Burst Mode, OPTI-LOOP and µModule are registered trademarks and n High Power Battery Operated Systems No RSENSE is a trademark of Analog Devices, Inc. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION Wide Input Range to 12V/8A Low IQ, Cascaded Boost+Buck Regulator
VIN 5V TO 38V 2mΩ 1µH VMID, 14V** 4.7µH 3mΩ VOUT DOWN TO 12V 2.5V AFTER + 33µF 6.8µF 6.8µF + 33µF 22µF + 47µF 8A* 499k 499k START-UP 46.4k 35.7k 4.7µF 0.1µF 0.1µF SENSE2– SENSE2+ BG2 SW2 BOOST2 TG2 INTVCC PGND VFB2 VBIAS TG1 BOOST1 SW1 BG1 SENSE1+ SENSE1– VFB1 LTC7812 EXTVCC RUN1 RUN2 ITH1 ITH2 TRACK/SS1 SS2 FREQ PLLIN/MODE SGND 0.1µF 15k 1.86k 100pF 820pF 0.01µF 4.7nF 6.8nF * WHEN VIN < 8V, MAXIMUM LOAD CURRENT AVAILABLE IS REDUCED ** VMID = 14V WHEN VIN < 14V V 7812 TA01a MID FOLLOWS VIN WHEN VIN > 14V 7812fc For more information www.linear.com/LTC7812 1 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Typical Application Related Parts