(

)

OUT

IN

DS(on)

OUT

V

V

DCR

r

I

=

-

+

g

TPS61252

www.ti.com

SLVSAG3A – SEPTEMBER 2010 – REVISED DECEMBER 2014

Feature Description (continued)

10.3.9 Thermal Regulation

The TPS61252 contains a thermal regulation loop that monitors the die temperature. If the die temperature rises

to values above 110 °C, the device automatically reduces the current limit to prevent the die temperature from

further increasing. Once the die temperature drops about 10 °C below the threshold, the device automatically

increases the current to the set value. This function also reduces the current during a short-circuit-condition.

10.3.10 Thermal Shutdown

mode, the High Side and Low Side MOSFETs are turned-off. When the junction temperature falls about 20 °C

below the thermal shutdown, the device resumes operation.

10.4 Device Functional Modes

10.4.1 Power Save Mode

The TPS61252 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 again once the output voltage exceeds the set

threshold voltage. During the power save operation when the output voltage is above the set threshold, the

converter turns off some of the inner circuits to save energy.

Figure 8. Power Save Mode

The PFM mode is left and PWM mode entered, in case the output current can no longer be supported in PFM

mode.

10.4.2 100% Duty-Cycle Mode

current limit operation with the use of the 100% duty-cycle mode. In this mode, the high-side switch is constantly

turned on. During this operation, the output voltage follows the input voltage and will not fall below the

depends on the load current and input voltage, and is calculated as:

where

•

DCR is the DC resistance of the inductor

•

(4)

If the load current exceeds the set current limit, the resistance of the high-side switch increases to limit the

current and the output voltage drops.

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