TC1054 Datasheet, PDF (6/18 Pages) TelCom Semiconductor, Inc – 50mA CMOS LDO WITH SHUTDOWN AND ERROR OUTPUT

TC1054/TC1055/TC1186
3.0 DETAILED DESCRIPTION
The TC1054, TC1055 and TC1186 are precision fixed
output voltage regulators. (If an adjustable version is
desired, please see the TC1070/TC1071/TC1187 data
sheet.) Unlike bipolar regulators, the TC1054, TC1055
and TC1186 supply current does not increase with load
current. In addition, V_OUT remains stable and within
regulation over the entire 0mA to I_OUTMAX operating
load current range, (an important consideration in RTC
and CMOS RAM battery back-up applications).
Figure 3-1 shows a typical application circuit. The
regulator is enabled any time the shutdown input
(SHDN) is at or above V_IH, and shutdown (disabled)
when SHDN is at or below V_IL. SHDN may be
controlled by a CMOS logic gate, or I/O port of a
microcontroller. If the SHDN input is not required, it
should be connected directly to the input supply. While
in shutdown, supply current decreases to 0.05µA
(typical), V_OUT falls to zero volts, and ERROR is open-
circuited.
FIGURE 3-1:
TYPICAL APPLICATION
CIRCUIT
+
1µF
+
Battery
V_IN
V_OUT
TC1054
TC1055
TC1186
GND
V_OUT
+
1µF
C1
Shutdown Control
(to CMOS Logic or Tie
to V_IN if unused)
SHDN ERROR
C2 Required Only
if ERROR is used as a
Processor RESET Signal
(See Text)
V+
R1
1M
0.2µF
C2
BATTLOW
or RESET
3.1 ERROR Open Drain 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 falls to V_TH, and
inactive when V_OUT rises above V_TH by V_HYS.
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 C2). R1 x C2 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:
ERROR OUTPUT
OPERATION
V_OUT
V_TH
HYSTERESIS (V_H)
ERROR
V_IH
V_OL
3.2 Output Capacitor
A 1µF (min) capacitor from V_OUT to ground is
recommended. The output capacitor should have an
effective series resistance greater than 0.1Ω and less
than 5.0Ω, 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 approxi-
mately -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.
DS21350B-page 6
© 2002 Microchip Technology Inc.