Datasheet

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Time = 500 nsec/div
V
O(RIPPLE)
= 10 mV/div (ac coupled)
I
O
= 14 A V
(PH )
= 1 V/div
Time = 10 msec/div
V
(SS/ENA)
= 1 V/div
V
O
= 1 V/div
Time = 200 sec/div
V
O
= 100 mV/div (ac coupled)
I
O
= 5 A/div
Time = 10 msec/div
VIN = 1 V/div
V
O
= 1 V/div
OPERATING WITH SEPARATE PVIN
TPS54010
SLVS509B – MAY 2004 – REVISED JUNE 2005
PERFORMANCE GRAPHS (continued)
START-UP WAVEFORM
OUTPUT VOLTAGE RELATIVE
OUTPUT VOLTAGE RIPPLE LOAD TRANSIENT RESPONSE TO ENABLE
Figure 31. Figure 32. Figure 33.
START-UP WAVEFORM
OUTPUT VOLTAGE RELATIVE
TO ENABLE
Figure 34.
NOTE:
DETAILED DESCRIPTION
If the PVIN input is controlled via a fast bus switch, it
results in a hard-start condition and may damage the
load (i.e., whatever is connected to the regulated
The TPS54010 is designed to operate with the power
output of the TPS54010). If a power-good signal is
stage (high-side and low-side MOSFETs) and the
not available from the 2.5-V power supply, one can
PVIN input connected to a separate power source
be generated using a comparator and hold the
from VIN. The primary intended application has VIN
SS/ENA pin low until the 2.5-V bus power is good. An
connected to a 3.3-V bus and PVIN connected to a
example of this is shown in Figure 35 . This circuit can
2.5-V bus. The TPS54010 cannot be damaged by
also be used to prevent the TPS54010 output from
any sequencing of these voltages. However, the
following the PVIN input while the PVIN power supply
UVLO (see detailed description section) is referenced
is ramping up.
to the VIN input. Some conditions may cause unde-
sirable operation.
If PVIN is absent when the VIN input is high, the
slow-start is released, and the PWM circuit goes to
maximum duty factor. When the PVIN input ramps
up, the output of the TPS54010 follows the PVIN
input until enough voltage is present to regulate to the
proper output value.
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