Synchronous buck controller ideal for stepping down high-voltage battery supply

The L3751 from STMicroelectronics is a synchronous dc-dc step-down power controller which can support extreme voltage-conversion ratios with good power efficiency. The L3751 operates from a very wide input-voltage range of 6 V to 75 V.

Operating from an input-voltage range of 6 V to 75 V, the L3751 provides an adjustable output of between 0.8 V and 60 V while switching at frequencies ranging from 100 kHz to 1 MHz. The controller is ideal for circuits that convert the output from a high-voltage battery or unregulated 24 V and 48 V bus to an application’s 12 V or 5 V power rail. 

In diode emulation mode, the L3751 implements a pulse-skipping function which maximizes efficiency at light loads, and limits output-voltage ripple. Forced PWM operation over the entire load range holds the switching frequency constant, and also minimizes output-voltage ripple. 

The controller features a Power Good output which validates the regulated output voltage: this is useful for implementing power sequencing during a digital IC power-up phase. 

The L3751 includes 7.5 V gate drivers compatible with standard MOSFETs, eliminating the need for external gate drivers in a converter circuit. Embedded protection functions include output over-current, under-voltage lockout, internal voltage monitoring, and thermal shutdown.  

Developers can use the ST eDesignSuite software tool to configure the L3751 buck converter for the application. The tool is available here.