A8113
AiT Semiconductor Inc.
HIGH POWER WHITE LED DRIVER
www.ait-ic.com
300mA ULTRA-LOW NOISE, ULTRA-FAST
Where: VREF=1.23V typ. (the internal reference voltage) Resistors R1 and R2 should be chosen for
approximately 50uA divider current. Lower value resistors can be used for improved noise performance, but
the solution consumes more power. Higher resistor values should be avoided as leakage current into/out of
FB across R1/R2 creates an offset voltage that artificially increases/decreases the feedback voltage and thus
erroneously decrease/increases VOUT. The recommended design procedure is to choose R2=30.1kΩ to set
the divider current at 50uA, C1=22pF for stability, and then calculate using Equation as below:
In order to improve the stability of the adjustable version, it is suggested that a small compensation capacitor
be placed between OUT and FB. The suggested value of this capacitor for several resistor ratios is shown in
the table below.
Output Voltage Programming Guide
Output Voltage
3.3V
R1
R2
R3
51 kΩ
30.1 kΩ
22pF
A8113 Adjustable Programming
Thermal Considerations
Thermal protection limits power dissipation in A8113. When the operation junction temperature exceeds
165°C, the OTP circuit starts the thermal shutdown function turn the pass element off. The pass element turns
on again after the junction temperature cools by 30°C.
For continue operation, do not exceed absolute maximum operation junction temperature 125°C. The power
dissipation definition in device is:
PD = (VIN−VOUT) ×IOUT + VIN×IQ
REV2.0
- JUN 2011 RELEASED, SEP 2012 REVISED -
- 9 -
AITSEMI [ AiT Semiconductor ]
