Multi-phase 60V synchronous boost controller protects I/O

A multi-phase synchronous boost DC/DC controller, the LTC3897, has an input surge stopper and ideal diode controller. The boost controller drives two N-channel power MOSFET stages out-of-phase to reduce input and output capacitor requirements, enabling the use of smaller inductors versus the single-phase equivalent.

The input surge stopper, with adjustable clamp voltage, controls the gate of an N-channel MOSFET to protect against high input voltage transients of greater than 100V and provides inrush current control, over-current protection and output disconnect. The integrated ideal diode controller drives another N-channel MOSFET for reverse input voltage protection and voltage holdup or peak detection.

The LTC3897 is for automotive, industrial and medical systems where a step-up DC/DC converter is needed to efficiently deliver high power in a small form factor. It can be configured to regulate a 24V/10A output from a car battery (12V) at up to 97 per cent efficiency, for example. The low 55 microA quiescent current in Burst Mode operation extends battery life and minimises power loss at light loads. The controller operates from an input ranging from 4.5 to 65V, with 75V peak. It can regulate an output voltage as high as 60V and the powerful onboard adjustable 5.0 to 10V gate drivers are capable of slewing large logic-level or standard threshold MOSFET gates quickly.

In keep-alive applications where the input voltage may exceed the regulated output voltage, the LTC3897 allows the synchronous MOSFET to be kept on continuously so that the output voltage follows the input voltage with minimal power loss. The current mode control architecture uses a phase-lockable frequency from 75 to 850kHz or fixed frequency adjustable from 50 to 900kHz.

Adjustable cycle-by-cycle current limit is also included, and the device can use a sense resistor or monitor the voltage drop across the inductor for current sensing. The boost controller, surge stopper and ideal diode can be shut down independently. In addition to an adjustable soft-start, it maintains ±1% reference voltage accuracy over an operating junction temperature range of -40 to +125 degree C. 

The LTC3897 is available in TSSOP-38 and 5.0 x 7.0mm QFN-38 packages. Three temperature grades are available: extended, industrial and a high temperature automotive range.


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