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AS1374

Datasheet - A p p l i c a t i o n I n f o r m a t i o n

9 Application Information

Capacitor Selection and Regulator Stability

For normal operation, use a 1µF capacitor at pin VDD and a 1µF capacitor at pin OUT. Larger input capacitor values

and lower ESR provide better noise rejection and line-transient response. Reduce output noise and improve load-tran-

sient response, stability, and power-supply rejection by using large output capacitors.

Note:

Some ceramic dielectrics exhibit large capacitance and ESR variation with temperature. With dielectrics such

as Z5U and Y5V, it may be necessary to use a 2.2µF or larger output capacitor to ensure stability at tempera-

tures below -10°C. With X7R or X5R dielectrics, 1µF is sufficient at all operating temperatures.

Noise, PSRR, and Transient Response

The AS1374 is designed to deliver ultra-low noise and high PSRR, as well as low dropout and low quiescent currents

in battery-powered systems. The power-supply rejection is 85dB at 1kHz and 50dB at 100kHz. (see Figure 8 on page

5).

When operating from sources other than batteries, improved supply-noise rejection and transient response can be

achieved by increasing the values of the input and output capacitors, and through passive filtering techniques.

The Figure 19, Figure 20 on page 7 and Figure 21 on page 8 show the AS1374 Load- and Line- Transient Responses.

Dropout Voltage

The AS1374 minimum dropout voltage determines the lowest usable supply voltage. In battery-powered systems, this

determines the useful end-of-life battery voltage.

Since the AS1374 use a P-channel MOSFET pass transistor, the dropout voltage is a function of drain-to-source on-