The TPS65281/TPS65281-1 incorporates an N-channel back-to-back power MOSFET switch and a
monolithic buck converter. The device is intended to provide a total power distribution solution
for digital TV, set-top boxes, tablet PC and VOIP phones etc applications, where precision current
limiting is required or heavy capacitive load or short circuit are encountered.
A 100-mΩ independent power distribution switch limits the output current to a
programmable current limit threshold between typical 75 mA and 2.7 A by using an external resistor.
The current limit accauracy as tight as ±6% can be achieved at higher current limit setting.
TPS65281 provides circuit breaker functionality by latching off the power switch during
over-current or reverse-voltage situations. TPS65281-1 limits output current to a safe level by
using a constant current mode when the output load exceeds the current limit threshold. An internal
reverse-voltage comparator disables the power switch when the output voltage is driven higher than
the input to protect the device on the input side of the switch in normal operation. The nFAULT
output asserts low under over-current and reverse-voltage conditions. Back-to-back power MOSFETs
structure prevents the reverse current injection from an active load at output port during shutdown
of power switch.
The buck DC/DC converter integrates power MOSFETs for optimized power efficiency and
reduced external component count. A wide 4.5-V to 18-V input supply range to buck encompasses most
intermediate bus voltages operating off 5-V, 9-V, 12-V or 15-V power bus. Constant frequency peak
current mode control simplifies the compensation and provides fast transient response. The buck can
be precisely sequenced and ramp up in order to align with other rails in the system with the
soft-start pin. With SS pin floating, the built-in 1ms soft-start time prevents in-rush current.
Cycle-by-cycle over current protection and hiccup operation limit MOSFET power dissipation in short
circuit or over loading fault conditions. The switching frequency of the converter can be
programmed from 300 kHz to 1.4 MHz with an external resistor at ROSC pin. With ROSC pin connecting
to V7V pin, floating, or grounding, a default fixed switching frequency can be selected to reduce
an external resistor.
The TPS65281/TPS65281-1 is available in a 16-lead thermally enhanced QFN (RGV) 4-mm ×
4-mm thin package.
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