1 Features

1• Wide Input Supply Voltage Range (4.5 to 18 V)

• 0.8 V, 1% Accuracy Reference

• Continuous Loading: 3 A (Buck 1),

2 A (Buck 2 and 3)

• Maximum Current: 3.5 A (Buck 1),

2.5 A (Buck 2 and 3)

• Adjustable Switching Frequency

300 kHz to 2.2 MHz Set by External Resistor

• Dedicated Enable for Each Buck

• External Synchronization Pin for Oscillator

• External Enable/Sequencing and Soft-Start Pins

• Adjustable Current Limit Set By External Resistor

• Soft-Start Pins

• Current-Mode Control With Simple Compensation

Circuit

• Powergood

• Optional Low-Power Mode Operation for Light

Loads

• VQFN Package, 40-Pin 6 mm × 6 mm RHA

2 Applications

• Set Top Boxes

• Blu-ray DVD

• DVR

• DTV

• Car Audio/Video

• Security Camera

3 Description

The TPS65251 features three synchronous wide

input range high efficiency buck converters. The

converters are designed to simplify its application

while giving the designer the option to optimize their

usage according to the target application.

The converters can operate in 5-, 9-, 12- or 15-V

systems and have integrated power transistors. The

output voltage can be set externally using a resistor

divider to any value between 0.8 V and close to the

input supply. Each converter features enable pin that

allows a delayed start-up for sequencing purposes,

soft-start pin that allows adjustable soft-start time by

choosing the soft-start capacitor, and a current limit

(RLIMx) pin that enables designer to adjust current

limit by selecting an external resistor and optimize the

choice of inductor. The current mode control allows a

simple RC compensation.

The switching frequency of the converters can either

be set with an external resistor connected to ROSC

pin or can be synchronized to an external clock

connected to SYNC pin if needed. The switching

regulators are designed to operate from 300 kHz to

2.2 MHz. 180° out of phase operation between Buck

1 and Buck 2, 3 (Buck 2 and 3 run in phase)

minimizes the input filter requirements.