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SLVSAA4B – JUNE 2010 – REVISED JANUARY 2011
4.5-V TO 18-V INPUT, HIGH CURRENT, SYNCHRONOUS STEP DOWN THREE BUCK
SWITCHER WITH INTEGRATED FET
Check for Samples:
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FEATURES
Wide Input Supply Voltage Range
(4.5 V - 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 - 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
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Soft Start Pins
Current-Mode Control With Simple
Compensation Circuit
Power Good
Optional Low Power Mode Operation for Light
Loads
QFN Package, 40-Pin 6 mm x 6 mm RHA
APPLICATIONS
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Set Top Boxes
Blu-ray DVD
DVR
DTV
Car Audio/Video
Security Camera
DESCRIPTION/ORDERING INFORMATION
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.
TPS65251 features a supervisor circuit that monitors each converter output. The PGOOD pin is asserted once
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.
TPS65251 also features a light load pulse skipping mode (PSM) by allowing the LOW_P pin tied to V3V. The
PSM mode allows for a reduction on the input power supplied to the system when the host processor is in
stand-by (low activity) mode.
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Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2010–2011, Texas Instruments Incorporated
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