APL5538 Anpec Electronics Corporation, APL5538 Datasheet - Page 11

• Manufacturer Part Number: APL5538
• Description: Dual Channel 300ma Regulator + Reset Ic
• Manufacturer: Anpec Electronics Corporation

APL5538
Capacitor Selection and Regulator Stabil-
ity
The APL5538 uses at least a 1uF capacitor on the
input. This capacitor can use Aluminum, Tantalum or
Ceramic capacitors. Input capacitor with large value
and low ESR provides better PSRR and line-transient
response. The output capacitor also can use
Aluminum, Tantalum or Ceramic capacitors, and it’ s
minimum values is recommended 2.2uF, ESR muse
be above 0.01 . Large output capacitor values can
reduce noise and improve load-transient response,
stability, and PSRR. Note that some ceramic dielec-
trics exhibit large capacitance and ESR variation with
Temperature. If use this capacitor, it may be neces-
sary to use 2.2uF or more to ensure stability at tem-
perature below -10 C.
Load-Transient Considerations
The APL5538 load-transient response graphs in Typi-
cal Characteristics show the transient response. A
step change in the load current from 1mA to 300mA
at 1u second will cause less than 200mV transient
spike. Large output capacitor’ s value and low ESR
can reduce transient spike.
Shutdown/Enable
The APL5538 has an active high enable function. Force
CONT high (>1.6V) enables the V
4V) disables the V
by CONT. Enter the shutdown mode, it also causes
the output voltage to discharge through a 500
tance to ground. In shutdown mode, the quiescent
current can reduce to 100uA. The CONT pin cannot
be floating, a floating CONT pin may cause an inde-
terminate state on the output. If it is no use, connect
to V
Copyright
Rev. A.6 - Jul., 2006
Application Information
IN
for normal operation.
ANPEC Electronics Corp.
OUT1
and V
OUT2
OUT1
can not be affected
, CONT low (<0.
resis-
11
RESET
The RESET pin is asserted whenever V
the reset threshold voltage or if CONT is forced low at
some special IC(refer timing chart and pin description).
The reset function ensures the microprocessor is prop-
erly reset and powers up into a known condition after
a power failure. RESET will remain valid with V
low as 0.95V. The RESET output is a simple open-
drain N channel MOSET structure. A pull-up resistor
must be used to pull this output up to some voltage.
For most application, this voltage will be the same
power supply that supplies V
APL5538 is relatively immune to negative-going
glitches below the reset threshold. Typically reset delay
time is 13ms while using o.1uF at Cd pin. If more
transient immunity is needed, a Cd capacitor can be
placed as larger as possible.
The minimun input-output voltage differential (dropout)
determines the lowest usable supply voltage. The drop-
out voltage is a function of drain-to-source on resis-
tance multiplied by the load current.
Current Limit
APL5538 includes two separate current-limit circuitry
for each linear regulator. The current limit protection,
which sense the current flows the P-channel MOSFET,
and controls the output voltage. The point where limit-
ing occurs is I
to ground for an indefinite amount of time without dam-
aging to the part.
Input-Output (Dropout)Voltage
OUT
=950mA. The output can be shorted
IN
to the APL5538. The
www.anpec.com.tw
DET
falls below
IN
as