The TPS54821 in thermally enhanced 3.5 mm × 3.5 mm QFN package is a full featured 17 V, 8
A synchronous step down converter which is optimized for small designs through high efficiency and
integrating the high-side and low-side MOSFETs. Further space savings are achieved through current
mode control, which reduces component count, and by selecting a high switching frequency, reducing
the inductor's footprint.
The output voltage startup ramp is controlled by the SS/TR pin which allows operation as
either a stand alone power supply or in tracking situations. Power sequencing is also possible by
correctly configuring the enable and the open drain power good pins.
Cycle by cycle current limiting on the high-side FET protects the device in overload
situations and is enhanced by a low-side sourcing current limit which prevents current runaway.
There is also a low-side sinking current limit which turns off the low-side MOSFET to prevent
excessive reverse current. Hiccup protection will be triggered if the overcurrent condition has
persisted for longer than the preset time. Thermal hiccup protection disables the device when the
die temperature exceeds the thermal shutdown temperature and enables the part again after the
built-in thermal shutdown hiccup time.
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