AS1367
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 the maximum over the entire device temperature
range, use a 3.3µF (min) ceramic output capacitor with an ESR <0.2Ω. 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:
VDROPOUT = VIN – VOUT = RDS(ON) × IOUT
(EQ 3)
Where:
RDS(ON) is the drain-to-source on-resistance.
IOUT is the output current.
Figure 17. Application Diagrams
External Voltage Level Detection
(Input Monitoring)
Internal Voltage Level Detection
(Output Monitoring)
Input
2V to 5.5V
Output
1.2V to 5.0V
Input
2V to 5.5V
Output
1.2V to 5.0V
OUT
IN
IN
OUT
C
C
IN
OUT
C
C
IN
OUT
AS1367
R
1µF
3.3µF
PU
AS1367
R
1µF
PU
3.3µF
100kΩ
100kΩ
IN
POK
IN
POK
C
10nF
BYP
C
10nF
BYP
ON /
OFF
ON /
OFF
BYP
EN
BYP
EN
GND
SET
R
ADJ
GND
SET
270kΩ
www.austriamicrosystems.com
Revision 1.02
11 - 14
AMSCO [ AMS(艾迈斯) ]
