ADP196ACPZN-01-R7 datasheet(11/12 Pages) AD

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Data Sheet

ADP196

Rev. 0 | Page 11 of 12

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 ADP196 includes circuitry that has

a typical 2 ms turn-on delay and a controlled rise time to limit

the VIN inrush current. As shown in Figure 25 and Figure 26,

the turn-on delay is nearly independent of the input voltage.

CH1 20mA

Ω

CH2 1V

M1ms

A CH2

1.18V

T 10.6%

CH3 500mV BW

VOUT

INPUT CURRENT

ENABLE

Figure 25. Typical Turn-On Time and Inrush Current, VIN = 1.8 V,

COUT = 47 μF, 330 Ω Load

CH1 20mA

Ω

CH2 1V

M1ms

A CH2

1.18V

T 10.6%

CH3 2V BW

VOUT

INPUT CURRENT

ENABLE

Figure 26. Typical Turn-On Time and Inrush Current, VIN = 5 V,

COUT = 47 μF, 330 Ω Load

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. The rise

time is dependent 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 ADP196; however, capacitors can be used to suppress noise

on the board.

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.

The turn-off time is also dependent on the RC time constant

of the output capacitance and load resistance. Figure 27 shows

typical turn-off times with VIN = 1.8 V to 5 V, COUT = 47 μF, and

RLOAD = 330 Ω.

1.0

2.0

3.0

4.0

5.0

6.0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

TIME (SEC)

VEN

VIN = 5.0V

VIN = 3.3V

VIN = 1.8V

Figure 27. Typical Turn-Off Time

CURRENT-LIMIT AND THERMAL OVERLOAD

PROTECTION

The ADP196 is protected against damage due to excessive power

dissipation by current-limit and thermal overload protection

circuits. The ADP196 is designed to limit current when the output

load reaches 4 A (typical). When the output load exceeds 4 A,

the output voltage is reduced to maintain a constant current limit.

Thermal overload protection is included, which limits the junction

temperature to a maximum of 125°C (typical). Under extreme

conditions (that is, high ambient temperature and/or high power

dissipation) when the junction temperature starts to rise above

125°C, the output is turned off, reducing the output current to

zero. When the junction temperature falls below 110°C, the

output is turned on again, and the output current is restored to

its operating value.

Consider the case where a hard short from VOUT to ground

occurs. At first, the ADP196 current limits so that only 4 A is

conducted into the short. If self-heating of the junction is great

enough to cause its temperature to rise above 125°C, thermal

shutdown is activated, turning off the output and reducing the

output current to zero. As the junction temperature cools and

falls below 110°C, the output turns on and conducts 4 A into

the short, again causing the junction temperature to rise above

125°C. This thermal oscillation between 110°C and 125°C causes a

current oscillation between 4 A and 0 mA that continues as long

as the short remains at the output.

Current-limit and thermal overload protections are intended to

protect the device against accidental overload conditions. For

reliable operation, device power dissipation must be externally

limited so that the junction temperature does not exceed 125°C.

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