Datasheet

V
OUT_NOM
+1%
PWMMode
medium/heavyload
PFMMode
lightload
Smooth
increasedload
PWMMode
medium/heavyload
PFMMode
lightload
Fastloadtransient
PWMMode
medium/heavyload
COMP_LOWthreshold-2%
95%
5%
t
RAMP
t
Startup
EN
V
OUT
Vin
min
+ Vout
max
) Iout
max
ǒ
RDSon
max
) R
L
Ǔ
TPS62400, TPS62401
TPS62402, TPS62403, TPS62404
SLVS681E –JUNE 2006–REVISED APRIL 2010 www.ti.com
At light loads, in which the converter operates in PFM Mode, the output voltage is regulated typically 1% higher
than the nominal value. In case of a load transient from light load to heavy load, the output voltage drops until it
reaches the skip comparator low threshold set to –2% below the nominal value and enters PWM mode. During a
load throw off from heavy load to light load, the voltage overshoot is also minimized due to active regulation
turning on the N-channel switch.
Figure 33. Dynamic Voltage Positioning
Soft Start
The two converters have an internal soft start circuit that limits the inrush current during start-up. During soft
start, the output voltage ramp up is controlled as shown in Figure 34.
Figure 34. Soft Start
100% Duty Cycle Low Dropout Operation
The converters offer a low input-to-output voltage difference while still maintaining operation with the use of the
100% duty cycle mode. In this mode the P-channel switch is constantly turned on. This is particularly useful in
battery-powered applications to achieve longest operation time by taking full advantage of the whole battery
voltage range. The minimum input voltage to maintain regulation depends on the load current and output voltage,
and can be calculated as:
(3)
with:
Iout
max
= maximum output current plus inductor ripple current
RDSon
max
= maximum P-channel switch RDSon.
R
L
= DC resistance of the inductor
Vout
max
= nominal output voltage plus maximum output voltage tolerance
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