AP2337

1.0A SINGLE CHANNEL CURRENT-LIMITED LOAD SWITCH

AP2337

Document number: DS35060 Rev. 2 - 2

8 of 10

www.diodes.com

September 2011

© Diodes Incorporated

Application Note (cont.)

Thermal Protection

Thermal protection prevents the IC from damage when the die temperature exceeds safe margins. This mainly occurs when

heavy-overload or short-circuit faults are present for extended periods of time. The AP2337 implements a thermal sensing to

monitor the operating junction temperature of the power distribution switch. Once the die temperature rises to approximately

150°C, the Thermal protection feature gets activated as follows: The internal thermal sense circuitry turns the power switch

off thus preventing the power switch from damage. Hysteresis in the thermal sense circuit allows the device to cool down to

approximately 20°C before the output is turned back on. This built-in thermal hysteresis feature is an excellent feature, as it

avoids undesirable oscillations of the thermal protection circuit. The switch continues to cycle in this manner until the load

fault is removed, resulting in a pulsed output.

Discharge Function

When input voltage is pulled, the discharge function is active. The output capacitor is discharged through an internal NMOS

that has a discharge resistance of 100

Ω. Hence, the output voltage drops down to zero. The time taken for discharge is

dependent on the RC time constant of the resistance and the output capacitor. Discharge time is calculated when UVLO

falling threshold is reached to output voltage reaching 300mV.

Power Dissipation and Junction Temperature

The low on-resistance of the internal MOSFET allows the small surface-mount packages to pass large current. Using the

2

Finally, calculate the junction temperature:

Where:

Ordering Information

AP 2337 SA - 7

7 : Tape & Reel

Package

Packing

SA : SOT23

Device

Package Code

Packaging

(Note 7)

7” Tape and Reel

Quantity

Part Number Suffix

AP2337SA-7

SA

SOT23

3000/Tape & Reel

-7

Notes:

7. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at

http://www.diodes.com/datasheets/ap02001.pdf.