Dual-channel synchronous buck controller is 100% duty-cycle capable

The Texas Instruments LM5137 is an 80V synchronous buck DC-DC controller from a family that offers three options for functional safety: Capable, SIL 2, and SIL 3. The device employs an interleaved, stackable, peak current-mode architecture, facilitating easy loop compensation, a fast transient response, exceptional load and line regulation, and accurate current sharing among paralleled phases for high output current.

A high-side switch with a minimum on-time of 22ns enables large step-down ratios, delivering direct conversion from 12V, 24V, or 48V inputs to low-voltage rails, thereby reducing system design cost and complexity. The device continues to operate during input voltage dips as low as 4V, at 100% duty cycle if needed. The 1.5µA sleep quiescent current, combined with output voltage regulation, extends operating run-time in battery-powered systems.

Several features are incorporated to simplify compliance with CISPR 11 and CISPR 32 EMI requirements. Adaptively timed, high-current MOSFET gate drivers minimise body diode conduction during switching transitions, lowering switching losses and enhancing thermal and EMI performance at high input voltage and high switching frequency. To reduce input capacitor ripple current and EMI filter size, 180° interleaved operation is supplied for two outputs. A 90° out-of-phase clock output works well for cascaded, multichannel or multiphase power stages. A resistor-adjustable switching frequency of up to 2.2MHz can be synchronised to an external clock source of up to 2.64MHz to eliminate beat frequencies in noise-sensitive applications.

Other features of the LM5137 include 150C maximum junction temperature operation, user-selectable PFM mode for lower current consumption during light-load conditions, configurable soft-start function, open-drain PG flags for fault reporting and output monitoring, independent enable inputs, monotonic start-up into prebiased loads, integrated VCC bias supply regulator powered from VIN or VOUT1, hiccup-mode overload protection, and thermal shutdown protection with automatic recovery. Current is sensed utilising the inductor DCR for the highest efficiency or an optional shunt resistor for high accuracy.

The LM5137 controller is available in a 6mm × 6mm, thermally enhanced, 36-pin VQFN package with extra pin clearance for increased reliability and wettable flank pins to enable optical inspection during manufacturing. The wide input voltage range, low quiescent current consumption, high-temperature operation, cycle-by-cycle current limit, low EMI signature, and compact design size make this an excellent point-of-load regulator choice for applications requiring enhanced robustness and durability.