4.0 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, VOUT
remains stable and within regulation over the entire
0 mA to ILOADMAX load current range (an important
consideration in RTC and CMOS RAM battery back-up
Figure 4-1 shows a typical application circuit.
+ 1 µF
(to CMOS Logic or Tie
to VIN, if unused)
C3 Required Only
if ERROR is used as a
Processor RESET Signal
Typical Application Circuit.
4.1 Output Capacitor
A 1 µF (min.) capacitor from VOUT to ground is
required. The output capacitor should have an Effective
Series Eesistance (ESR) greater than 0.1 and less
than 5. A 1 µF capacitor should be connected from
VIN to GND if there is either more than 10 inches of wire
between the regulator and the AC filter capacitor or 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 by employing passive filtering
4.2 ERROR Output
ERROR is driven low whenever VOUT falls out of
regulation by more than – 5% (typ.). This condition may
be caused by low input voltage, output current limiting
or thermal limiting. The ERROR threshold is 5% below
rated VOUT, regardless of the programmed output
voltage value (e.g., ERROR = VOL 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 4-2.
Note that ERROR is active when VOUT is at or below
VTH, and inactive when VOUT is above VTH + VHYS.
As shown in Figure 4-1, 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 VIH of the processor
RESET input for at least 200 ms to allow time for the
system to stabilize. Pull-up resistor R1 can be tied to
VOUT, VIN or any other voltage less than (VIN + 0.3V).
ERROR Output Operation.
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