AS1364
Datasheet - Application Information
9 Application Information
Capacitor Selection and Regulator Stability
Input and output capacitors are required for stable operation of the AS1364 over the full temperature range and with
load currents up to 1A. Connect CIN and COUT as close to the AS1364 as possible to minimize the impact of PC board
trace inductance.
Input Capacitor
For CIN, a 4.7µF capacitor between IN and ground is sufficient. CIN reduces the source impedance of the input supply
and may be smaller than 4.7µF if powered from regulated power supplies or low-impedance batteries. Larger input
capacitor values and lower ESR provide better noise rejection and line-transient response.
Output Capacitor
A 4.7µF low-ESR capacitor between OUT and ground is sufficient for COUT. The output capacitor’s ESR affects stabil-
ity and output noise. An output capacitors with an ESR of 0.5Ω or less is recommended to ensure stability and opti-
mum transient response. Reduced output noise and improve load-transient response, stability, and power-supply
rejection by using large output capacitors with low ESR.
Noise, PSRR, and Transient Response
AS1364 output noise is typically 10µVRMS (100Hz to 100kHz) or 45µVRMS (10Hz to 1MHz) during normal operation.
This is suitably low for most applications (see Figure 10 on page 7).
The AS1364 is designed to achieve extremly low dropout voltage and low quiescent current in battery-powered sys-
tems while still maintaining excellent noise performance, transient response, and PSRR. See the Figure 11 on page 7
for a plot of power-supply rejection ratio (PSRR) versus frequency.
When operating from very noisy sources, the factory preset variants a recommanded since they offer improved noise
performance over the adjustable variants.
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