PAM2800

Document number: DSxxxxx Rev. 1 - 3

4 of 7

www.diodes.com

October 2012

© Diodes Incorporated

PAM2800

A Product Line of

Diodes Incorporated

Application Information

In the typical application (see Figure 1), the LED current will come to constant current level little by little after the device is powered. A 62ΚΩ

resistor is recommended for R1, the value for R2 should be adjusted around 33ΚΩ due to LED forward voltage from lot-to-lot or brand-to-brand.

Power Dissipation and Thermal Consideration

Thermal protection limits power dissipation in the PAM2800. When the operation junction temperature exceeds +150°C, the OTP (Over

Temperature Protection) starts the thermal shutdown and turns the pass transistor off. The pass transistor resumes operation after the junction

temperature drops below +120°C.

For continuous operation, the junction temperature should be maintained below +125°C. The power dissipation is defined as:

()

I

*

V

I

*

V

V

P

GND

IN

O

OUT

IN

D

+

−

=

The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surrounding airflow and temperature

difference between junction and ambient. The maximum power dissipation can be calculated by the following formula:

(

−

=

JA

A

)

MAX

(

J

)

MAX

(

D

/

T

T

P

junction to the ambient.

(

)

W

4

.

0

250

/

C

25

C

125

P

)

MAX

(

D

=

°

−

°

=

()

mW

360

A

70

*

V

4

mA

300

*

V

8

.

2

V

4

≈

μ

+

−

=