AS1363
Datasheet - Application Information
9 Application Information
Capacitor Selection and Regulator Stability
Input and output capacitors are required for stable operation of the AS1363 over the full temperature range and with
load currents up to 500mA. Connect CIN and COUT as close to the AS1363 as possible to minimize the impact of PC
board trace inductance.
For CIN, connect a 1µF capacitor between IN and ground. CIN lowers the source impedance of the input supply.
Reduce noise and improve load-transient response, stability, and power supply rejection by using larger output capac-
itors, such as 10µF.
For COUT connect a 2.2µF low-ESR capacitor between OUT and ground. The output capacitor’s ESR affects stability
and output noise. Use output capacitors with an ESR of 0.1Ω or less to ensure stability and optimum transient
response. Surface-mount ceramic capacitors have very-low ESR and are commonly available in values up to 10µF.
For output voltages less than 2V, use a 4.7µF low-ESR output capacitor for COUT.
Noise, Power Supply Rejection Ratio, and Transient Response
The AS1363 is designed to operate with low dropout voltages and low quiescent currents in battery-powered systems
while still maintaining good noise response, transient response, and AC rejection. See Typical Operating Characteris-
tics on page 6 for a plot of power-supply rejection ratio (PSRR) versus frequency. When operating from noisy sources,
improved supply-noise rejection and transient response can be achieved by increasing the values of the input and out-
put bypass capacitors and through passive filtering techniques.
Dropout Voltage
Because the AS1363 uses a P-channel MOSFET pass transistor, its dropout voltage is a function of drain-to-source
on-resistance (RDS(ON)) multiplied by the load current:
VDROPOUT = VIN – VOUT = RDS(ON) × IOUT
Note: The AS1363 ground current remains below 200µA in dropout.
(EQ 4)
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