Data Sheet

ADPL40502

analog.com

Rev. 0

13 of 17

The ADPL40502 uses an internal soft start to limit the inrush current when the output is enabled. The start-up time

for the 3.3V option is approximately 180µs from the time the EN active threshold is crossed to when the output

reaches 90% of its final value. Figure 26 shows typical EN active and inactive thresholds when the input voltage varies

from 2.2V to 5.5V.

Figure 26.Typical Start-Up Behavior

Current-Limit and Thermal Overload Protection

The ADP40502 is protected against damage due to excessive power dissipation by current and thermal overload

protection circuits. The ADPL40502 is designed to current limit when the output load reaches 300mA (typical). When

the output load exceeds 300mA, 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 150°C (typical).

Under extreme conditions (i.e., high ambient temperature and power dissipation) when the junction temperature

starts to rise above 150°C, the output is turned off, reducing the output current to 0. When the junction temperature

drops below 135°C, the output is turned on again, and the output current is restored to its nominal value.

Consider the case where a hard short from VOUT to ground occurs. At first, the ADPL40502 current limits, so that only

300mA is conducted into the short. If self heating of the junction causes its temperature to rise above 150°C, thermal

shutdown activates, turning off the output and reducing the output current to 0. As the junction temperature cools

and drops below 135°C, the output turns on and conducts 300mA into the short, again causing the junction

temperature to rise above 150°C. This thermal oscillation between 135°C and 150°C causes a current oscillation

between 300mA and 0mA that continues as long as the short remains at the output.

Current-limit and thermal limit protections protect the device against accidental overload conditions. For reliable

operation, device power dissipation must be externally limited so that junction temperatures do not exceed 125°C.

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

0

450

400

350

300

250

200

150

100

50

TIME (µs)

ENABLE

3.3V

2.8V