TC1263 Datasheet, PDF (4/14 Pages) Microchip Technology – 500mA Fixed Output CMOS LDO with Shutdown

TC1263
3.0 DETAILED DESCRIPTION
The TC1263 is a precision, fixed output LDO. Unlike
bipolar regulators, the TC1263’s supply current does
not increase with load current. In addition, V_OUT
remains stable and within regulation over the entire
0mA to I_LOADMAX load current range (an important
consideration in RTC and CMOS RAM battery back-up
applications).
Figure 3-1 shows a typical application circuit.
FIGURE 3-1:
TYPICAL APPLICATION
CIRCUIT
+
+
1µF
C2
Battery
V_IN
V_OUT
TC1263
GND
+
1µF
C1
V_OUT
Shutdown Control
(to CMOS Logic or Tie
to V_IN if unused)
SHDN
ERROR
C3 Required Only
if ERROR is used as a
Processor RESET Signal
(See Text)
V⁺
R1
1M
+
C3 0.2µF
BATTLOW
or RESET
3.1 Output Capacitor
A 1µF (min) capacitor from V_OUT to ground is required.
The output capacitor should have an effective series
resistance greater than 0.1Ω and less than 5Ω, and a
resonant frequency above 1MHz. A 1µF capacitor
should be connected from V_IN to GND if there is more
than 10 inches of wire between the regulator and the
AC filter capacitor, or if a battery is used as the power
source. Aluminum electrolytic or tantalum capacitor
types can be used. (Since many aluminum electrolytic
capacitors freeze at approximately -30°C, solid
tantalums are recommended for applications operating
below -25°C.) When operating from sources other than
batteries, supply-noise rejection and transient
response can be improved by increasing the value of
the input and output capacitors and employing passive
filtering techniques.
3.2 ERROR Output
ERROR is driven low whenever V_OUT falls out of
regulation by more than – 5% (typical). This condition
may be caused by low input voltage, output current
limiting, or thermal limiting. The ERROR threshold is
5% below rated V_OUT regardless of the programmed
output voltage value (e.g., ERROR = V_OL at 4.75V
(typ.) for a 5.0V regulator and 2.85V (typ.) for a 3.0V
regulator). ERROR output operation is shown in
Figure 3-2.
Note that ERROR is active when V_OUT is at or below
V_TH, and inactive when V_OUT is above V_TH + V_H.
As shown in Figure 3-1, ERROR can be used as a
battery low flag, or as a processor RESET signal (with
the addition of timing capacitor C3). R1 x C3 should be
chosen to maintain ERROR below V_IH of the processor
RESET input for at least 200 msec to allow time for the
system to stabilize. Pull-up resistor R1 can be tied to
V_OUT, V_IN or any other voltage less than (V_IN + 0.3V).
FIGURE 3-2:
V_OUT
ERROR OUTPUT
OPERATION
V_TH
HYSTERESIS (V_H)
ERROR
V_IH
V_OL
DS21374B-page 4
© 2002 Microchip Technology Inc.