APL5901-26VC datasheet(11/21 Pages) ANPEC

11 / 21 page

Rev. B.2 - May., 2005

APL5901/2

www.anpec.com.tw

Thermal protection limits total power dissipation in the

device. When the junction temperature exceeds

J=+150℃, the thermal sensor generates a logic sig-

nal to turn off the pass transistor and allows IC to

cool. When the IC’s junction temperature is down by

10℃, the thermal sensor will turn the pass transistor

on again, resulting in a pulsed output during continu-

ous thermal protection. Thermal protection is designed

to protect the APL5901/2 in the ev ent of fault

conditions. For continuous operation, do not exceed

the absolute maximum junction temperature of

J=+150℃.

Operating Region and Power Dis-

sipation

The thermal resistance of the case to circuit board,

and the rate of air flow all control the APL5901/2’s

maximum power dissipation. The power dissipation

across the device is P

D = IOUT (VIN-VOUT) and the maxi-

mum power dissipation is:

DMAX = (TJ-TA) / (θ JC + θ CA)

where T

J-TA is the temperature difference between the

junction and ambient air, θ

JC is the thermal resis-

tance of the package, and θ

CA is the thermal resis-

tance through the printed circuit board, copper traces,

and other materials to the ambient air.

The GND pin of the APL5901 provide an electrical con-

nection to ground and channeling heat away. If power

dissipation is large, connect the GND pin to ground

using a large pad or ground plane, can improve the

problem of over heat of IC.

Thermal Protection

APL5901-26VC Datasheet(PDF) 11 Page - Anpec Electronics Coropration