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LOW-DROPOUT OPERATION 100% DUTY CYCLE

ENABLE

UNDERVOLTAGE LOCKOUT

SHORT-CIRCUIT PROTECTION

THERMAL SHUTDOWN

TPS62300, TPS62301, TPS62302

TPS62303, TPS62305, TPS62311

TPS62313, TPS62320, TPS62321

SLVS528B – JULY 2004 – REVISED JUNE 2005

DETAILED DESCRIPTION (continued)

In 100% duty cycle mode, the TPS6230x, TPS6231x, and TPS6232x offer a low input-to-output voltage

difference. In this mode, the P-channel MOSFET is constantly turned on. This is particularly useful in

battery-powered applications to achieve the longest operation time by taking full advantage of the whole battery

voltage range. The minimum input voltage to maintain regulation, depending on the load current and output

voltage, can be calculated as:

•

•

•

•

•

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

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. When an output voltage is present during shutdown mode,

which can be caused by an external voltage source or super capacitor, the reverse leakage is specified under

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

In addition, the TPS6232x devices integrate a resistor, typically 35

Ω, to actively discharge the output capacitor

The undervoltage 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 TPS6231x devices have a UVLO threshold set to 2 V (typical). Fully functional operation is permitted down

to 2.4 V input voltage. EN is set low for input voltages lower than 2.4 V to avoid the possibility of misoperation.

TPS6231x devices are to be considered where the user requires direct control of the turn-off sequence as part of

a larger power management system.

As soon as the output voltage falls below 50% of the nominal output voltage, the converter current limit is

reduced by 50% of the nominal value. Because the short-circuit protection is enabled during start-up, the device

does not deliver more than half of its nominal current limit until the output voltage exceeds 50% of the nominal

output voltage. This needs to be considered when a load acting as a current sink is connected to the output of

the converter.

mode, the P- and N-channel MOSFETs are turned off. The device continues its operation when the junction

temperature falls below typically 130

°C again.

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