VIN

UVLO

ENABLE

Thermal

Protection

Reference

Overcurrent

GateDrive

Oscillator

Ramp

Generator

VREF

PH

ENA

GND

BOOT

Z1

Z2

SHDN

SHDN

SHDN

SHDN

SHDN

SHDN

SHDN

SHDN

VIN

112.5%VREF

VSENSE

OVP

HICCUP

HICCUP

SHDN

NC

FeedForward

BOOT

NC

POWERPAD

VIN

VOUT

5 µA

1.221VBandgap

SlowStart

Boot

Regulator

Error

Amplifier

Gain=25

PWM

Comparator

Protection

Gate

Driver

Control

VSENSE

TPS5450

SLVS757D – MARCH 2007 – REVISED DECEMBER 2014

www.ti.com

7 Detailed Description

7.1 Overview

The TPS5450 device is a 36-V, 5-A, step-down (buck) regulator with an integrated high-side n-channel MOSFET.

The device implements constant-frequency voltage-mode control with voltage feed forward for improved line

regulation and line transient response. Internal compensation reduces design complexity and external component

count.

The integrated 110-m

Ω high-side MOSFET supports high-efficiency power-supply designs capable of delivering

5-A of continuous current to a load. The gate-drive bias voltage for the integrated high-side MOSFET is supplied

by a bootstrap capacitor connected from the BOOT to PH pins. The TPS5450 device reduces the external

component count by integrating the bootstrap recharge diode.

The TPS5450 device has a default input start-up voltage of 5.3 V typical. The ENA pin can be used to disable

the TPS5450 reducing the supply current to 18 µA. An internal pullup current source enables operation when the

EN pin is floating. The TPS5450 includes an internal slow-start circuit that slows the output rise time during start-

up to reduce in rush current and output voltage overshoot.

The minimum output voltage is the internal 1.221-V feedback reference. Output overvoltage transients are

minimized by an Overvoltage Protection (OVP) comparator. When the OVP comparator is activated, the high-

side MOSFET is turned off and remains off until the output voltage is less than 112.5% of the desired output

voltage.

Internal cycle-by-cycle overcurrent protection limits the peak current in the integrated high-side MOSFET. For

continuous overcurrent fault conditions the TPS5450 will enter hiccup mode overcurrent limiting. Thermal

protection protects the device from overheating.

7.2 Functional Block Diagram

8

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