A6300
AiT Semiconductor Inc.
www.ait-ic.com
LOW DROPOUT VOLTAGE REGULATOR
300mA CMOS WITH ENABLE PIN
A6300 in SOT-25 package, the thermal resistance θJA is 250℃ on the standard JEDEC 51-3 single-layer
thermal test board. The maximum power dissipation at TA = 25℃ can be calculated by following formula:
PD(MAX) = (125℃ - 25℃) / 250 = 0.4W
The value of junction to case thermal resistance θJC is popular to users. This thermal parameter is convenient
for users to estimate the internal junction operated temperature of packages while IC operating. It’s
independent of PCB layout, the surroundings airflow effects and temperature difference between junction to
ambient. The operated junction temperature can be calculated by following formula:
TJ = TC + PD*θJC
Where TC is the package case temperature measured by thermal sensor, PD is the power dissipation defined
by user’s function and the θJC is the junction to case thermal resistance provided by IC manufacturer.
Therefore it’s easy to estimate the junction temperature by any condition.
Example for Junction Temperature
To calculate the junction temperature of A6300 in SOT-25 package.
If we use input voltage VIN = 3.3V, at an output current IO = 300mA and the case temperature TC = 70℃
measured by the thermal couple while operating, then our power dissipation is as follows:
PD = (3.3V – 2.8V) * 300mA + 3.3V * 70μA 210mW
And the junction temperature TJ could be calculated as following:
TJ = TC + PD *θJC
TJ = 70℃ + 0.21W * 130℃/W = 70℃ + 27.3℃ = 97.3℃ < TJ(MAX) = 125℃
For this operation application, TJ is lower than absolute maximum operation junction temperature 125℃ and
it’s safe to use.
REV1.4
- JUN 2006 RELEASED, FEB 2015 UPDATED -
17
AITSEMI [ AiT Semiconductor ]
