ADP197 Data Sheet
Rev. C | Page 12 of 13
TIMING
Turn-on delay is defined as the interval between the time that
V
EN
exceeds the rising threshold voltage and when V
OUT
rises to
~10% of its final value. The ADP197 includes circuitry that has a
typical 1 ms turn-on delay and a controlled rise time to limit the
V
IN
inrush current. As shown in Figure 29 and Figure 30, the turn-
on delay is nearly independent of the input voltage.
CH1 100mA
CH3 2V
CH2 1V M1.00ms A CH3 1.28V
3
1
2
T 10.20%
B
W
B
W
Ω
B
W
CH1 AMPL
204mA
09298-027
I
LOAD
V
OUT
V
EN
Figure 29. Typical Turn-On Delay Time with V
IN
= 1.9 V, I
LOAD
= 200 mA
3
2
1
CH1 AMPL
222mA
CH1 100mA
CH3 2V
CH2 2V M1.00ms A CH3 1.28V
T 10.00%
B
W
B
W
Ω
B
W
09298-028
I
LOAD
V
OUT
V
EN
Figure 30. Typical Turn-On Delay Time with V
IN
= 5.5 V, I
LOAD
= 220 mA
The rise time is defined as the time it takes the output voltage to
rise from 10% to 90% of V
OUT
reaching its final value. It is depen-
dent on the rise time of the internal charge pump.
For very large values of output capacitance, the RC time constant
(where C is the load capacitance (C
LOAD
) and R is the RDS
ON
||R
LOAD
)
can become a factor in the rise time of the output voltage. Because
RDS
ON
is much smaller than R
LOAD
, an adequate approximation
for RC is RDS
ON
× C
LOAD
. An input or load capacitor is not
required for the ADP197 although capacitors can be used to
suppress noise on the board. Figure 31 and Figure 32 show the
inrush current when C
LOAD
is 100 µF.
3
2
1
CH1 AMPL
266mA
CH1 100mA
CH3 2V
CH2 2V M1.00ms A CH3 1.28V
T 10.00%
B
W
B
W
Ω
B
W
09298-029
I
LOAD
V
OUT
V
EN
Figure 31. Typical Rise Time and Inrush Current,
C
LOAD
= 100 μF, V
IN
= 1.9 V, I
LOAD
= 270 mA
3
2
1
CH1 AMPL
352mA
CH1 200mA
CH3 2V
CH2 2V M1.00ms A CH3 1.28V
T 10.00%
B
W
B
W
Ω
B
W
09298-030
I
LOAD
V
OUT
V
EN
Figure 32. Typical Rise Time and Inrush Current,
C
LOAD
= 100 μF, V
IN
= 5.5 V, I
LOAD
= 350 mA
The turn-off time is defined as the time it takes for the output
voltage to fall from 90% to 10% of V
OUT
reaching its final value. It
is also dependent on the RC time constant of the output capacit-
ance and load resistance. Figure 33 shows the typical turn-off
time with V
IN
= 3.6 V, C
OUT
= 1 µF, and R
LOAD
= 18 .
CH1 1V CH2 1V M20µs A CH1 240mV
1
2
T 20.20%
B
W
B
W
09298-031
V
EN
V
OUT
Figure 33. Typical Turn-Off Time
