AS1371
Datasheet - Application Information
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 400mA over the entire device temperature
range, use a 1µF (min) ceramic output capacitor with an ESR <0.2Ω. Use large output capacitor values (e.g. 10µF) 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.
Power Supply Rejection Ratio
The AS1371 is designed to deliver low dropout voltages and low quiescent currents. Power-supply rejection is typically
50dB at 10kHz. To improve power supply-noise rejection and transient response, increase the values of the input and
output bypass capacitors, which are shown in Figure 14.
The Section 6 Electrical Characteristics on page 4 show also the device line- and load-transient responses.
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 is calculated by:
VDROPOUT = VIN – VOUT = RDS(ON) × IOUT
(EQ 4)
Where:
RDS(ON) is the drain-to-source on -resistance.
IOUT is the output current.
Figure 14. Application Diagrams
External Voltage Level Detection
(Input Monitoring)
Internal Voltage Level Detection
(Output Monitoring)
Input
1.2V to 3.6V
Input
1.2V to 3.6V
Output
0.6V to 3.3V
Output
0.6V to 3.3V
OUT
IN
OUT
IN
C
1µF
ON /
OFF
C
IN
1µF
C
C
IN
OUT
OUT
R
PU
R
1µF
1µF
PU
AS1371
AS1371
100kΩ
100kΩ
ON /
OFF
EN
POK
EN
POK
GND
SENSE
GND
SENSE
R
R
1
2
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