TPS62230, TPS62231, TPS62232, TPS62233

TPS62234, TPS62235, TPS62236, TPS62237

TPS62238, TPS62239, TPS622310, TPS622311

www.ti.com

SLVS941B – APRIL 2009 – REVISED DECEMBER 2009

UNDER VOLTAGE LOCKOUT

The under voltage lockout circuit prevents the device from misoperation at low input voltages. It prevents the

converter from turning on the switch or rectifier MOSFET under undefined conditions. The TPS6223X devices

have a UVLO threshold set to 1.8V (typical). Fully functional operation is permitted for input voltage down to the

falling UVLO threshold level. The converter starts operation again once the input voltage trips the rising UVLO

threshold level.

SOFT START

The TPS6223X has an internal soft-start circuit that controls the ramp up of the output voltage and limits the

inrush current during start-up. This limits input voltage drops when a battery or a high-impedance power source

is connected to the input of the converter.

The soft-start system generates a monotonic ramp up of the output voltage and reaches the nominal output

voltage typically 100

μs after EN pin was pulled high.

Should the output voltage not have reached its target value by this time, such as in the case of heavy load, the

converter then operates in a current limit mode set by its switch current limits.

TPS6223X is able to start into a pre-biased output capacitor. The converter starts with the applied bias voltage

and ramps the output voltage to its nominal value.

ENABLE / SHUTDOWN

The device starts operation when EN is set high and starts up with the soft start as previously described. For

proper operation, the EN pin must be terminated and must not be left floating.

Pulling the EN pin low forces the device into shutdown, with a shutdown quiescent current of typically 0.1

μA. In

this mode, the P and N-channel MOSFETs are turned off, the internal resistor feedback divider is disconnected,

and the entire internal-control circuitry is switched off.

The EN input can be used to control power sequencing in a system with various DC/DC converters. The EN pin

can be connected to the output of another converter, to drive the EN pin high and getting a sequencing of supply

rails.

SHORT-CIRCUIT PROTECTION

The TPS6223X integrates a High Side and Low Side MOSFET current limit to protect the device against heavy

load or short circuit. The current in the switches is monitored by current limit comparators. When the current in

the P-channel MOSFET reaches its current limit, the P-channel MOSFET is turned off and the N-channel

MOSFET is turned on to ramp down the current in the inductor. The High Side MOSFET switch can only turn on

again, once the current in the Low Side MOSFET switch has decreased below the threshold of its current limit

comparator.

THERMAL SHUTDOWN

mode, the High Side and Low Side MOSFETs are turned-off. The device continues its operation when the

junction temperature falls below the thermal shutdown hysteresis.

Copyright © 2009, Texas Instruments Incorporated

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Product Folder Link(s): TPS62230 TPS62231 TPS62232 TPS62233 TPS62234 TPS62235 TPS62236 TPS62237

TPS62238 TPS62239 TPS622310 TPS622311