AiT Semiconductor Inc.
A6303C
www.ait-ic.com
CMOS LOW DROPOUT REGULATOR (LDO)
300mA ULTRA-LOW NOISE, ULTRA-FAST RESPONSE
ambient temperature. The junction to ambient thermal resistance (θJA is layout dependent) for SOT-25
package is 250°C/W, on standard JEDEC 51-3 thermal test board. The maximum power dissipation at
TA=25°C can be calculated by following formula:
PD(MAX) = (125°C−25°C)/250 = 400mW (SOT-25)
The maximum power dissipation depends on operating ambient temperature for fixed TJ(MAX) and thermal
resistance θJA. It is also useful to calculate the junction of temperature of the A6303C under a set of specific
conditions. In this example let the Input voltage VIN=3.3V, the output current IO=300mA and the case
temperature TA=40°C measured by a thermal couple during operation. The power dissipation for the
VOUT=2.8V version of the A6303C can be calculated as:
PD = (3.3V−2.8V) ×300mA+3.6V×100uA =150mW
And the junction temperature, TJ, can be calculated as follows:
TJ=TA+PD×θJA=40°C+0.15W×250°C/W
=40°C+37.5°C=77.5°C<TJ(MAX) =125°C
For this operating condition, TJ is lower than the absolute maximum operating junction temperature,125°C, so
it is safe to use the A6303C in this configuration.
Layout considerations
To improve ac performance such as PSRR, output noise, and transient response, it is recommended that the
PCB be designed with separate ground planes for VIN and VOUT, with each ground plane connected only at the
GND pin of the device.
REV1.0
- AUG 2018 RELEASED -
- 9 -
AITSEMI [ AiT Semiconductor ]
