The TPS65251-x 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 an 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 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
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.