1 Features

• AEC-Q100 qualified for automotive applications:

– Device temperature grade 1: –40°C to +125°C

ambient operating temperature

– Operation up to 150°C junction temperature

– Thermally enhanced package provides

exposed top and bottom thermal pads and

enables dual-side cooling

• Functional Safety-Capable

– Documentation available to aid functional safety

system design

• Designed for Low EMI

– Symmetrical input voltage pins with > 1mm

clearance to ground

– Pin selectable spread spectrum option

– Pin selectable FPWM or auto mode operation

– Enhanced HotRod™ QFN (25) package with

wettable flanks

– Switching frequency from 100kHz to 2.2MHz

– Meets CISPR 25 class 5 EMI requirements

• Single and dual-output features

– Wide input voltage range of 3V to 36V

– 1% accurate fixed 3.3V, 5V or adjustable

outputs from 0.8V to 20V

– Hiccup-mode overcurrent protection and

thermal shutdown protection with hysteresis

– Precision ENABLE and PGOOD functions

– 50ns tON(min) for high VIN / VOUT ratio

– 80ns tOFF(min) for low dropout

• Versatile dual-output operation

– Shutdown mode current: 0.5μA typical

– No-load standby current: 9μA typical

– Built-in compensation and 3ms soft start

– Independent precision ENABLE and PGOOD

• Adaptable single-output operation

– > 95% efficient for an 8A load, single output,

VIN =12V, VOUT = 5V

– External compensation and adjustable soft start

– PGOOD, SYNCIN, and SYNCOUT functions

• Pin-to-pin Compatible with LMQ644A2-Q1

2 Applications

• Automotive cockpit and display

• Automotive ADAS and central compute

• Body electronics and lighting

• General-purpose dual buck converters

3 Description

The LM644A2-Q1 is a 36V, synchronous, buck,

DC/DC converter for high-current single or dual

outputs. The device uses an interleaved, stackable,

current-mode control architecture for easy loop

compensation, fast transient response, excellent load

and line regulation, and accurate current sharing with

an output clock supporting up to 6 phases for currents

up to 36A. A high-side switch minimum on-time of

50ns gives large step-down ratios, enabling the direct

conversion from 12V, 24V, or automotive inputs to

low-voltage rails for reduced system complexity and

design cost.

The LM644A2-Q1 incorporates spread spectrum in

an optimized enhanced HotRod QFN package, with

wettable flanks, and low inductance input bypass

configuration to minimize EMI. Dual Random Spread

Spectrum (DRSS) frequency hopping is set to

±10% (typical), drastically reducing emissions through

a combination of triangular and pseudo-random

modulation. A bias pin allows the LM644A2-Q1

to save losses by powering the device from the

output of the converter, achieving a 9μA no-load

quiescent current to extend the operating run-time

in battery-powered systems. The LM644A2-Q1 can

maintain high efficiency light-load operation even

when stacking multiple devices for high efficiency over

the full load range.