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CMPWR280
Typical Transient Characteristics
The transient characterization test set-up shown in
Figure 6 includes the effective source impedance of
the V
CC
supply (R
S
). This was measured to be approx-
imately 0.1Ω. It is recommended that this effective
source impedance be no greater than 0.15Ω to ensure
precise switching is maintained during V
CC
selection
and deselection.
Both the rise and fall times during V
CC
power-up/down
sequencing were controlled at a 10 millisecond dura-
tion. This is considered to represent worst case condi-
tions for most application circuits.
During a selection or deselection transition, the DC
load current is switching from V
AUX
to V
CC
and vice
versa. In addition to the normal load current, there may
also be an in-rush current for charging/discharging the
load capacitor.
The total current pulse being applied to either V
AUX
or
V
CC
is equal to the sum of the DC load and the corre-
sponding in-rush current. Transient currents in excess
of 1.0 amps can readily occur for brief intervals when
either supply commences to power the load.
Figure 6. Transient Performance Test Set-up
V
CC
Load Transient Response is shown in Figure 7
for a step load from 15mA to 1500mA. An overshoot of
approximately 300mV is observed, before settling
within 3µs.
Figure 7. V
CC
Load Transient Response
V
SBY
Load Transient Response is shown in Figure 8
is shown for a step load from 5mA to 375mA. An over-
shoot of approximately 100mV is observed, before set-
tling within 1µs.
Figure 8. V
SBY
Load Transient Response
