APL5901 Anpec Electronics Corporation, APL5901 Datasheet - Page 10

• Manufacturer Part Number: APL5901
• Description: Low I , Low Dropout 900ma Fixed Voltage Regulator Q
• Manufacturer: Anpec Electronics Corporation

APL5901/2
Copyright
Rev. B.2 - May., 2005
Application Information
Capacitor Selection and Regulator
Stability
The APL5901/2 use at least a 1 F capacitor on the
input, and this capacitor can be Aluminum, Tantalum
or Ceramic capacitor. The input capacitor with larger
value and lower ESR provides better PSRR and line-
transient response. The output capacitor also can use
Aluminum, Tantalum or Ceramic capacitor, and a mini-
mum value of 4.7 F and ESR above 0.02
recommended. A larger output capacitor can reduce
noise and improve load-transient response, stability,
and PSRR. Note that some ceramic dielectrics ex-
hibit large capacitance and ESR variation with
temperature. When using this capacitor, a minimum
10uF or more may be required to ensure the stability
at low temperature operation. Use a bypass capaci-
tor at BP pin for low output nvise. Increasing the ca-
pacitance will slightly decrease the output noise, but
increase the start-up time.
Load-Transient Considerations
The APL5901/2 load-transient response graphs in typi-
cal characteristics show the transient response. A
step change in the load current from 10mA to 900mA
at 10 s will cause a 20mV transient spike. Larger
output capacitor and lower ESR can reduce transient
spike.
Input-Output (Dropout)Voltage
The minimum input-output voltage difference (dropout)
determines the lowest usable supply voltage. In bat-
tery-powered systems, this will determine the useful
end-of-life battery voltage. Because the APL5901/2
use a p-channel MOSFET pass transistor, the drop-
out voltage is a function of drain-to-source on-resis-
tance (R
DS(ON)
ANPEC Electronics Corp.
) multiplied by the load current.
is
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Shutdown/Enable
The APL5901/2 have an active high enable function.
Force EN high (>1.6V) enables the regulator, EN low
(<0.4V) disables the regulator and enter the shutdown
mode. In shutdown mode, the quiescent current can
reduce below 1uA. The EN pin cannot be floating, a
floating EN pin may cause an indeterminate state on
the output. If it is no use, connect to V
operation.
Current Limit
The APL5901/2 have a current limit protection. The
ouptut voltage will drop close to zero volt, when load
current reaches the limit, and then the load current
will be limited at 200mA after output voltage is below
0.7V. When the load current back to the value where
limiting started, the output voltage and current will re-
turn to normal value. When output is shorted to
ground, the APL5901/2 will keep short circuit current
at 200mA .
Reverse Current Protection
The APL5901/2 have an internal reverse protection, it
does not need an external schottky diode to connect
the regulator input and output. If the output voltage is
forced above the input voltage by more than 11mV,
the IC will be shutdown and the ground pin current is
below 0.1uA.
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IN
for normal