Data Sheet

ADPL44002

analog.com

Rev. 0

18 of 23

Current-Limit and Thermal Overload

The ADPL44002 is protected against damage due to excessive power dissipation by current and thermal overload

protection circuits. The ADPL44002 is designed to current limit when the output load reaches 360mA (typical). When

the output load exceeds 360mA, 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 (that is, high ambient temperature and/or high power dissipation), when the junction

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

junction temperature drops below 135°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 ADPL44002 current limits, so that only

360mA is conducted into the short. If self heating of the junction is great enough to cause its temperature to rise

above 150°C, thermal shutdown activates, turning off the output and reducing the output current to zero. As the

junction temperature cools and drops below 135°C, the output turns on and conducts 360mA 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 360mA and 0mA that continues as long as the short remains at the output.

Current and thermal limit protections 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°.

PRINTED CIRCUIT BOARD LAYOUT CONSIDERATIONS

Heat dissipation from the package can be improved by increasing the amount of copper attached to the pins of the

ADPL44002. However, a point of diminishing returns is eventually reached, beyond which an increase in the copper

size does not yield significant heat dissipation benefits.

Place the input capacitor as close as possible to the VIN pin and GND pin. Place the output capacitor as close as

possible to the VOUT and GND pins. The use of 0805 or 1206 size capacitors and resistors achieves the smallest possible

footprint solution on boards where area is limited.