PAM3101 datasheet(13/24 Pages) PAM

13 / 24 page

Thermal considerations

Thermal protection limits power dissipation in the

PAM3101. When the 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

c ontinuous

operation,

the

junction

temperature should be maintained below 125°C.

The power dissipation is defined as:

P = (V -V

)*I +V *I

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:

Where T

is the maximum allowable junction

temperature 125°C, T is the ambient temperature

and

is the thermal resistance from the junction

to the ambient.

For example, as

is 250°C/W for the SOT-23

package and 180°C/W for the SOT-89 package

based on the standard JEDEC 51-3 for a single-

layer thermal test board, the maximum power

dissipation at T =25°C can be calculated by

following formula:

= (125°C-25°C)/250=0.4W

SOT-23

= (125°C-25°C)/180=0.55W

SOT-89

It is also useful to calculate the junction

temperature of the PAM3101 under a set of

specific conditions. For example, suppose the

input voltage V =3.3V, the output current

I =300mA and the case temperature T =40°C

measured by a thermalcouple during operation,

the power dissipation for the Vo=2.8V version of

the PAM3101 can be calculated as:

P =(3.3V-2.8V)*300mA+3.3V*70 A

150mW

And the junction temperature, T , can be

calculated as follows:

T= T

T = 40°C+0.15W*250°C/W

=40°C+37.5°C

=77.5°C<T

= 125°C

For this operating condition, T is lower than the

absolute

m aximum

operating

junction

temperature, 125°C, so it is safe to use the

PAM3101 in this configuration.

OUT

GND

J(MAX)

D(MAX)

J(MAX)

= (T

-T )/θ

+P *θ

D(MAX)

J(MAX)

≌

09/2008 Rev 1.4

Power Analog Microelectronics Inc

www.poweranalog.com

PAM3101

300mA High PSRR Low Dropout CMOS Linear Regulator

PAM3101 数据表(PDF) 13 Page - Power Analog Micoelectronics

PAM3101 数据表(HTML) 13 Page - Power Analog Micoelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

数据表下载

链接网址

PAM3101 数据表(PDF) 13 Page - Power Analog Micoelectronics

PAM3101 数据表(HTML) 13 Page - Power Analog Micoelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

数据表 下载

链接网址

数据表下载