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TPS61256C

SLVSDQ1 – FEBRUARY 2017

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Feature Description (continued)

Once the output capacitor has been biased to the input voltage, the converter starts switching. The soft-start

system progressively increases the on-time as a function of the input-to-output voltage ratio. As soon as the

output voltage is reached, the regulation loop takes control and full current operation is permitted.

The TPS61256xC works in the pass-through mode when EN is low and Vin above UVLO, the device enters into

the boost switching phase directly when EN becomes high.

9.3.4 Undervoltage Lockout

The under voltage lockout circuit prevents the device from malfunctioning at low input voltages and the battery

threshold plus its hysteresis of 100 mV at typically 2.1 V.

9.3.5 Thermal Regulation

The TPS61256xC device contains a thermal regulation loop that monitors the die temperature during the pre-

charge phase. If the die temperature rises to high values of about 110 °C, the device automatically reduces the

current to prevent the die temperature from increasing further. Once the die temperature drops about 10 °C

below the threshold, the device will automatically increase the current to the target value. This function also

reduces the current during a short-circuit condition.

9.3.6 Thermal Shutdown

mode, the high-side and low-side MOSFETs are turned-off. When the junction temperature falls below the

thermal shutdown minus its hysteresis, the device continuous the operation.

9.4 Device Functional Modes

9.4.1 Power Save Mode

The TPS61256xC integrates a power save mode to improve efficiency at light load. In power save mode the

converter only operates when the output voltage trips below a set threshold voltage.

It ramps up the output voltage with several pulses and goes into power save mode once the output voltage

exceeds the set threshold voltage.

The PFM mode is left and PWM mode entered in case the output current can not longer be supported in PFM

mode.

Figure 9. Power Save