80V, 100% duty-cycle capable, dual-channel, functional safety synchronous buck controller

The LM5137F is an 80V, 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, 24V, or 48V inputs to low-voltage rails for reduced system design cost and complexity. The LM5137F

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 LM5137F 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.

The LM5137F 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.