LM25137F

The LM25137F is a 42V, dual-channel, buck controller offered from a family with three options for functional safety: Capable, SIL 2, or SIL 3. The device uses an interleaved, stackable, peak current-mode architecture for easy loop compensation, fast transient response, excellent load and line regulation, and accurate current sharing with paralleled phases for high output current. A high-side switch minimum on-time of 22ns facilitates large step-down ratios, enabling the direct conversion from 12V and 24V inputs to low-voltage rails for reduced system design cost and complexity. The LM25137F continues to operate during input voltage dips as low as 4V, at 100% duty cycle if needed.

Several features are included to simplify compliance with CISPR 11 and CISPR 32 EMI requirements. Adaptively timed, high-current MOSFET gate drivers minimize body diode conduction during switching transitions, reducing switching losses and improving 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 provided for two outputs. A 90° out-of-phase clock output works well for cascaded, multi-channel or multiphase power stages. Resistor-adjustable switching frequency as high as 2.2MHz can be synchronized to an external clock source up to 2.64MHz to eliminate beat frequencies in noise-sensitive applications.

The 1.8µA sleep quiescent current with the output voltage in regulation extends operating run-time in battery-powered systems. Additional features of the LM25137F include 150°C maximum junction temperature operation, user-selectable PFM mode for lower current consumption at light-load conditions, configurable soft-start functions, open-drain FAULT and 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 using an optional shunt resistor for high accuracy. Specific features for functional safety applications, including ABIST at start-up, VOUT1/2 and VCC ripple detection, redundant bandgap with error monitoring, redundant and fast VOUT1/2 monitoring, feedback path failure detection, and redundant thermal shutdown significantly reduces FIT rate.

The LM25137F controller comes in a 6mm × 6mm thermally-enhanced, 36-pin VQFN package with additional pin clearance for increased reliability. Also included are wettable flank pins to facilitate 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 small design size provide an excellent point-of-load regulator design for functional safety (FuSa) applications requiring enhanced robustness and durability.