Hitachi 55293DLB, Service Manual

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TPS54821
General Description
The TPS54821 in thermally enhanced 3.5 mm x 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.
Features

Integrated 26 m
Ω
/ 19 m
Ω
MOSFETs

Split Power Rail: 1.6 V to 17 V on PVIN

200 kHz to 1.6 MHz Switching Frequency

Synchronizes to External Clock

0.6V
±
1% Voltage Reference Over Temperature

Low 2
μ
A Shutdown Quiescent Current

Monotonic Start-Up into Pre-biased Outputs

–
40
°
C to 125
°
C Operating Junction Temperature Range

Adjustable Input Undervoltage Lockout

Adjustable Slow Start/Power Sequencing

Power Good Output Monitor for Undervoltage and Overvoltage

Adjustable Input Undervoltage Lockout
Applications

Digital TV Power Supplies

Set Top Boxes

Blu-ray DVDs

Home Terminals