TPS54332

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SLVS875C – JANUARY 2009 – REVISED NOVEMBER 2014

7 Detailed Description

7.1 Overview

The TPS54332 is a 28-V, 3.5-A, step-down (buck) converter with an integrated high-side, N-channel MOSFET.

To improve performance during line and load transients, the device implements a constant-frequency, current

mode control, which reduces output capacitance and simplifies external frequency compensation design. The

TPS54332 has a pre-set switching frequency of 1 MHz.

The TPS54332 needs a minimum input voltage of 3.5 V to operate normally. The EN pin has an internal pullup

current source that can be used to adjust the input voltage undervoltage lockout (UVLO) with two external

resistors. In addition, the pullup current provides a default condition when the EN pin is floating for the device to

operate. The operating current is 82

μA typically when not switching and under no load. When the device is

disabled, the supply current is 1

μA typically.

The integrated 80-m

Ω high-side MOSFET allows for high-efficiency power supply designs with continuous output

currents up to 3.5 A.

The TPS54332 reduces the external component count by integrating the boot recharge diode. The bias voltage

for the integrated high-side MOSFET is supplied by an external capacitor on the BOOT to PH pin. The boot

capacitor voltage is monitored by an UVLO circuit and will turn the high-side MOSFET off when the voltage falls

below a preset threshold of 2.1 V typically. The output voltage can be stepped down to as low as the reference

voltage.

By adding an external capacitor, the slow-start time of the TPS54332 can be adjustable which enables flexible

output filter selection.

To improve the efficiency at light load conditions, the TPS54332 enters a special pulse-skipping Eco-Mode when

the peak inductor current drops below 160 mA typically.

The frequency foldback reduces the switching frequency during start-up and over current conditions to help

control the inductor current. The thermal shutdown gives the additional protection under fault conditions.

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Product Folder Links: TPS54332