Datasheet

TPS61260, TPS61261

www.ti.com

SLVSA99A –MAY 2011–REVISED FEBRUARY 2013

Softstart and Short Circuit Protection

During startup of the converter, the duty cycle and the peak current are limited in order to avoid high peak

currents flowing from the input. After being enabled, the device starts operating. Until the output voltage reaches

about 0.4 V, the average output current ramps up from zero to the programmed value, as the output voltage

increases. As soon as the output current has reached the programmed value, it stays regulated at that value until

the load conditions demand less current. This typically happens when the output capacitor is charged and the

output voltage is regulated.

During startup, the device can seamlessly change modes of operation. When the input voltage is higher than the

output voltage, the device operates in a linear mode using the rectifying switches for control. If the input voltage

is lower than the output voltage it operates in a standard boost conversion mode. The boost conversion is non-

synchronous when the output voltage is below approximately 1.8 V and it is synchronous if the output voltage is

higher than approximately 1.8 V.

At short circuit conditions at the output, the output current is limited to the programmed average current. If the

short at the output causes the output voltage to drop below 0.4 V, the average current decreases approximately

linearly with the output voltage down to zero.

The device can monotonically start into a pre-bias on the output.

Undervoltage Lockout

An undervoltage lockout function prevents device startup if the supply voltage on VIN is lower than the

undervoltage lockout threshold defined in the ELECTRICAL CHARACTERISTICS table. When in operation, the

device automatically shuts down the power stage if the voltage on VIN drops below the undervoltage lockout

threshold. The device automatically restarts if the input voltage recovers to the minimum operating input voltage.

Output Overvoltage Protection

If, for any reason, the output voltage of the device (as measured at the VOUT pin) exceeds its maximum

recommended value, the device stops operating. It continues operating as soon as the output voltage has

dropped below this threshold.