The TPS65280 incorporates dual N-channel MOSFET power switches for USB power distribution
systems that require dual power switches in a single package. It also integrates a buck converter
which regulates an accurate 5-V output voltage from a 5.5-V to 18-V power bus to supply the power
for power switches. The device is intended to provide a total USB power distribution solution for
digital TV, set-top boxes, VOIP phones and tablet PC applications, where precision current limiting
is required or heavy capacitive loads or short circuits are encountered.
A dual 85-mΩ independent power distribution switch limits the output current to a typical 1.2 A (manufacture trim 0.8 A, 1.6 A, and 2 A available options) when output current load exceeds the current limit threshold. TPS65280 device limits output current to a safe level by using a
constant current mode when output load exceeds the current limit threshold. After delitching time,
TPS65280 provides circuit breaker functionality by latching off the power switch during over-current or reverse-voltage situations. Two back-to-back power MOSFETs prevent the current injects from output to input in shutdown. An internal reverse-voltage comparator disables the power switch when the output voltage is driven higher than the input to protect the circuits on the input side of the switch in normal operation. The nFAULT1/2 output asserts low during over-current and reverse-voltage conditions.
The buck DC/DC converter integrates power MOSFETs for optimized power efficiency and
reduced external component count for a fixed 5-V output voltage. A wide 5.5-V to 18-V input supply
range to buck encompasses most intermediate bus voltages operating off a 9-V, 12-V or 15-V power
bus. Constant frequency peak current mode control simplifies the compensation and fast transient
response. Equipped with enable and soft-start pins, the DC/DC can be precisely sequenced and ramp
up in order to align with other rails in the system. Cycle-by-cycle over-current protection and
operating in hiccup mode limit MOSFET power dissipation during buck output 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 the ROSC pin. With the ROSC pin connecting to the V7V pin,
floating, or grounding, a default fixed switching frequency can be selected to reduce the external
component. The internal oscillator can be synchronized with a free-run external clock in frequency.
When continuous heavy overload or short circuit increases power dissipation in the buck
converter or power switches, the internal thermal protection circuit shuts off both the buck
regulator and power switches to prevent damage. Recovery from a thermal shutdown is automatic once
the device has cooled sufficiently.
The TPS65280 is available in a 24-lead thermally enhanced QFN (RGE) 4-mm × 4-mm thin
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