PWM controller delivers output currents of 20A

24th January 2015

Siobhan O'Gorman

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Datasheet

Designed for negative-to-negative or negative-to-positive DC/DC conversion, the LT8709 synchronous PWM controller has been introduced by Linear Technology. The device is unique in solving the problem of regulating a negative voltage with respect to system ground, without the need of complicated level shifting circuitry.

Due to the PWM controller’s synchronous operation, the output diode is replaced with a high efficiency P-channel MOSFET, which increases efficiency, allows for higher output currents of up to 20A and eliminates the need for a heat sink. The LT8709 can be configured in buck, boost, buck-boost and inverting topologies, making it suitable for a wide range of power supply designs.

The device operates across an input voltage range of -4.5 to -806V with output voltages of -0.1 to 60V or -1.4 to -80V. Featuring a rail-to-rail output current monitor and control, the PWM controller can be configured as a current source. The LT8709 is offered with innovative EN/FBIN pin circuitry for slowly varying input signals and an adjustable undervoltage lockout function. To avoid collapsing a high impedance supply, this pin can also be used for input voltage regulation.

The device’s fixed operating frequency is selectable from 100 to 750kHz and can be synchronised to an external clock. Outstanding line and load regulation is provided by current mode control. The PWM controller can be configured for either forced continuous or pulse-skipping operating modes during light load conditions. Additional features include a power good indicator, thermal shutdown and integrated soft-start circuitry.

The LT8709 is available now in a 20-lead TSSOP, priced from $3.65 each and sold in 1,000-piece quantities.