42V, 100% duty-cycle capable dual-channel synchronous buck controller | RHA | 36

The LM25137 is a 42V

synchronous buck DC/DC controller offered from a family with three options

for functional safety: Capable, SIL

2, and 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 LM25137 continues to operate during input voltage

dips as low as 4V, at 100% duty cycle if needed. The 1.5µA sleep quiescent current

with the output voltage in regulation extends operating run-time in

battery-powered systems.

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, multichannel 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.

Additional

features of the LM25137 include 150°C 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 using the inductor DCR for highest efficiency or an optional shunt resistor for

high accuracy.

The LM25137 controller comes in a 6mm × 6mm, thermally-enhanced,

36-pin VQFN package with additional pin clearance for increased reliability and

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 choice for applications requiring enhanced

robustness and durability.