AS1367 datasheet(11/14 Pages) AMSCO

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AS1367

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

Ceramic capacitors are highly recommended as they offer distinct advantages over their tantalum and aluminum

electrolytic components. For stable operation with load currents up to the maximum over the entire device temperature

range, use a 3.3µF (min) ceramic output capacitor with an ESR <0.2

Ω. Use large output capacitor values (10µF max)

to reduce noise and improve load transient-response, stability and power-supply rejection.

Note: Some ceramic capacitors exhibit large capacitance and ESR variations with variations in temperature. Z5U

and Y5V capacitors may be required to ensure stability at temperatures below TAMB = -10ºC. With X7R or X5R

capacitors, a 3.3µF capacitor should be sufficient at all operating temperatures.

Power Supply Rejection Ratio

The AS1367 are designed to deliver low dropout voltages and low quiescent currents. Power-supply rejection is

typically 60dB at 10kHz. To improve power supply-noise rejection and transient response, increase the values of the

input and output bypass capacitors.

The Electrical Characteristics on page 4 show also the device line- and load-transient responses. For further details

see the Power-Supply Rejection Ratio vs. Frequency graph in the Figure 9 on page 7.

Dropout Voltage

For standard products with output voltage greater than the minimum VIN (1.2V), the minimum input-output voltage

differential (dropout voltage) determines the lowest usable supply voltage. This determines the useful end-of-life

battery voltage in battery-powered systems. The dropout voltage is a function of the P-MOSFET drain-to-source on-

resistance multiplied by the load current, and it is calculated by:

Where:

RDS(ON) is the drain-to-source on-resistance.

IOUT is the output current.

Figure 17. Application Diagrams

(EQ 3)

DROPOUT

OUT

–

DS ON

()

OUT

270k

RADJ

External Voltage Level Detection

(Input Monitoring)

Internal Voltage Level Detection

(Output Monitoring)

Input

2V to 5.5V

CIN

1µF

COUT

3.3µF

BYP

OUT

AS1367

POK

GND

SET

ON /

OFF

CBYP

10nF

Input

2V to 5.5V

CIN

µF

COUT

3.3µF

Output

1.2V to 5.0V

BYP

OUT

AS1367

POK

GND

SET

ON /

OFF

CBYP

10nF

Output

1.2V to 5.0V

RPU

100k

RPU

100k

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