1 Features

• Wide input supply voltage range (4.5 to 18 V)

• Output range: 0.8 V to VIN – 1 V

• 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

• Adjustable current limit set by external resistor

• Soft-start pins

• Current-mode control with simple compensation

circuit

• Power good

• Automatic PFM/PWM operation

• 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-x features three synchronous wideinput

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 an enable

pin that allows a delayed start-up for sequencing

purposes, soft-start pin that allows adjustable softstart

time by choosing the soft-start capacitor, and a

current limit (RLIMx) pin that enables the 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 the 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.

TPS65251-x features a supervisor circuit that

monitors each converter output. The PGOOD pin is

asserted when sequencing is done, all PG signals are

reported and a selectable end of reset time lapses.

The polarity of the PGOOD signal is active high.

All converters feature an automatic low-power pulse

PFM skipping mode, which improves efficiency during

light loads and standby operation, while ensuring a

very-low output ripple, allowing for a value of less than

2% at low output voltages.