New Industry Products

2-Phase Synchronous Buck Controller Supports Large Step-Down Ratios

November 02, 2019 by Paul Shepard

The LM5143-Q1 from Texas Instruments, Inc. is a 65-V synchronous buck dc-dc controller for high-current single or dual outputs. The device uses an interleaved, stackable, peak current-mode control architecture for easy loop compensation, fast transient response, excellent load and line regulation, and accurate current sharing with paralleled phases for higher output current.

A high-side switch minimum on-time of 65ns gives large step-down ratios, enabling the direct conversion from 12-V, 24-V or 48-V automotive inputs to low-voltage rails for reduced system complexity and solution cost. The LM5143-Q1 continues to operate during input voltage dips as low as 3.5V, at nearly 100% duty cycle if needed.

Current is sensed using the inductor DCR for highest efficiency or an optional shunt resistor for high accuracy. The 15-µA no-load quiescent current with the output voltage in regulation extends operating run-time in battery-powered systems. Power the LM5143-Q1 from the output of the switching regulator or another available source for even lower input quiescent current and power loss.

LM5143-Q1 simplified block diagram

Several features are included to simplify compliance with CISPR 25 and automotive EMI requirements. Adaptively timed, high-current MOSFET gate drivers with adjustable slew rate control 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 multi-phase power stages. Resistor-adjustable switching frequency as high as 2.2MHz can be synchronized to an external clock source up to 2.5MHz to eliminate beat frequencies in noise-sensitive applications. Optional triangular spread spectrum modulation further improves the EMI signature.

Additional features of the LM5143-Q1 include 150°C maximum junction temperature operation, user-selectable diode emulation for lower current consumption at light-load conditions, configurable soft-start functions, open-drain Power-Good flags for fault reporting and output monitoring, independent enable inputs, monotonic start-up into prebiased loads, integrated VCC bias supply regulator, programmable hiccup-mode overload protection, and thermal shutdown protection with automatic recovery.

The LM5143-Q1 controller comes in a 6-mm × 6-mm thermally-enhanced, 40-pin VQFNP package with wettable flank pins to facilitate optical inspection during manufacturing.