Datasheet

f
D
L
V
ΔI
IN
L
×=
I =I
VALLEY LIM
I
L
f
I
PEAK
Rectifier
Current
I
OUT(DC)
Inductorr
Current
Increased
LoadCurrent
I
I
N(DC)
I
IN(DC)
CurrentLimit
Threshold
I
OUT(CL)
DI
L
DI
L
PFMmodeatlightload
PWMmodeatheavyload
Output
Voltage
PFMrippleabout0.015xV
OUT
1.006xV
OUT NOM.
V
OUT NOM.
TPS61240, TPS61241
www.ti.com SLVS806B –APRIL 2009– REVISED FEBRUARY 2012
Figure 17. Inductor/Rectifier Currents in Current Limit Operation
POWER-SAVE MODE
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.
UNDER-VOLTAGE LOCKOUT
The under voltage lockout circuit prevents the device from malfunctioning at low input voltages and from
excessive discharge of the battery. It disables the output stage of the converter once the falling V
IN
trips the
under-voltage lockout threshold V
UVLO
. The under-voltage lockout threshold V
UVLO
for falling V
IN
is typically 2.0V.
The device starts operation once the rising VIN trips under-voltage lockout threshold V
UVLO
again at typ. 2.1V.
INPUT OVER-VOLTAGE PROTECTION
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 © 2009–2012, Texas Instruments Incorporated 11