f

D

L

V

I

IN

L

×

=

I

=I

VALLEY

LIM

IL

f

Rectifier

Current

Inductorr

Current

Increased

LoadCurrent

CurrentLimit

Threshold

POWER-SAVE MODE

PFMmodeatlightload

PWMmodeatheavyload

Output

Voltage

UNDER-VOLTAGE LOCKOUT

INPUT OVER-VOLTAGE PROTECTION

TPS61240, TPS61241

Figure 17. Inductor/Rectifier Currents in Current Limit Operation

The TPS6124x family of devices 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.

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

In the event of an overvoltage condition appearing on the input rail, the output voltage will also experience the

overvoltage due to being in dropout condition. A input overvoltage protection feature has been implemented into

the TPS6124x which has an input overvoltage threshold of 6.0V. Once this level is triggered, the device will go

into a shutdown mode to protect itself. If the voltage drops to 5.9V or below, the device will startup once more

into normal operation.

Copyright © 2009, Texas Instruments Incorporated

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Product Folder Link(s) :TPS61240, TPS61241