A8113
AiT Semiconductor Inc.
HIGH POWER WHITE LED DRIVER
www.ait-ic.com
300mA ULTRA-LOW NOISE, ULTRA-FAST
DETAILED INFORMATION
Applications Information
Like any low-dropout regulator, the external capacitors used with the A8113 must be carefully selected for
regulator stability and performance. Using a capacitor whose value is > 1μF on the A8113 input and the
amount of capacitance can be increased without limit. The input capacitor must be located a distance of not
more than 0.5 inch from the input pin of the IC and returned to a clean analog ground. Any good quality
ceramic or tantalum can be used for this capacitor. The capacitor with larger value and lower ESR (equivalent
series resistance) provides better PSRR and line-transient response. The output capacitor must meet both
requirements for minimum amount of capacitance and ESR in all LDOs application. The A8113 is designed
specifically to work with low ESR ceramic output capacitor in space-saving and performance consideration.
Using a ceramic capacitor whose value is at least 1μF with ESR is > 25mΩ on the A8113 output ensures
stability. The A8113 still works well with output capacitor of other types due to the wide stable ESR range.
Output capacitor of larger capacitance can reduce noise and improve load transient response, stability, and
PSRR. The output capacitor should be located not more than 0.5 inch from the VOUT pin of the A8113 and
returned to a clean analog ground.
Bypass Capacitor and Low Noise
Connecting a 22nF between the BP pin and GND pin significantly reduces noise on the regulator output, it is
critical that the capacitor connection between the BP pin and GND pin be direct and PCB traces should be as
short as possible. There is a relationship between the bypass capacitor value and the LDO regulator turn on
time. DC leakage on this pin can affect the LDO regulator output noise and voltage regulation performance.
Enable Function
The A8113 features an LDO regulator enable/disable function. To assure the LDO regulator will switch on; the
EN turn on control level must be greater than 1.2 volts. The LDO regulator will go into the shutdown mode
when the voltage on the EN pin falls below 0.4 volts. For to protect the system, the A8113 have a quick
discharge function. If the enable function is not needed in a specific application, it may be tied to VIN to keep
the LDO regulator in a continuously on state.
Programming the A8113 Adjustable LDO regulator
The output voltage of the A8113 adjustable regulator is programmed using an external resistor divider as
show in Figure as below. The output voltage is calculated using equation as below:
REV2.0
- JUN 2011 RELEASED, SEP 2012 REVISED -
- 8 -
AITSEMI [ AiT Semiconductor ]
