A6300A
AiT Semiconductor Inc.
www.ait-ic.com
LOW DROPOUT VOLTAGE REGULATOR
300mA CMOS ULTRA LOW NOISE AND FAST RESPONSE
Where TJ(MAX) is the maximum operation junction temperature 125℃, TA is the ambient temperature and the
θJA is the junction to ambient thermal resistance. For recommended operating conditions specification of
A6300A, where TJ(MAX) is the maximum junction temperature of the die (125℃) and TA is the maximum
ambient temperature. The junction to ambient thermal resistance (θJA is layout dependent) for SOT-23 AND
SOT-25 package are 250℃/W, on standard JEDEC 51-3 thermal test board. The maximum power dissipation
at TA= 25℃ can be calculated by following formula:
PD(MAX) = (125℃−25℃)/250 = 400mW (SOT-23 & 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 A6300A 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℃ measured by a thermal couple during operation. The power dissipation for the VO=2.8V
version of the A6300A 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℃+0.15W×250℃/W =40℃+37.5℃=77.5℃<TJ(MAX) =125℃
For this operating condition, TJ is lower than the absolute maximum operating junction temperature,125°C,
so it is safe to use the A6300A 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. In addition, the ground connection for the bypass capacitor should connect directly to
the GND pin of the A6300A.
REV1.4
-FEB 2010 RELEASED, DEC 2012 UPDATE –
- 9 -
AITSEMI [ AiT Semiconductor ]
