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.