ADP197

Data Sheet

Rev. C | Page 12 of 13

TIMING

Turn-on delay is defined as the interval between the time that

VEN exceeds the rising threshold voltage and when VOUT 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

VIN 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

ILOAD

VOUT

VEN

Figure 29. Typical Turn-On Delay Time with VIN = 1.9 V, ILOAD = 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

ILOAD

VOUT

VEN

Figure 30. Typical Turn-On Delay Time with VIN = 5.5 V, ILOAD = 220 mA

The rise time is defined as the time it takes the output voltage to

rise from 10% to 90% of VOUT 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 (CLOAD) and R is the RDSON||RLOAD)

can become a factor in the rise time of the output voltage. Because

RDSON is much smaller than RLOAD, an adequate approximation

for RC is RDSON × CLOAD. 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 CLOAD 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

ILOAD

VOUT

VEN

Figure 31. Typical Rise Time and Inrush Current,

CLOAD = 100 μF, VIN = 1.9 V, ILOAD = 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

ILOAD

VOUT

VEN

Figure 32. Typical Rise Time and Inrush Current,

CLOAD = 100 μF, VIN = 5.5 V, ILOAD = 350 mA

The turn-off time is defined as the time it takes for the output

voltage to fall from 90% to 10% of VOUT 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 VIN = 3.6 V, COUT = 1 μF, and RLOAD = 18 Ω.

CH1 1V

CH2 1V

M20µs

A CH1

240mV

1

2

T 20.20%

B

W

B

W

VEN

VOUT

Figure 33. Typical Turn-Off Time