TC1054_12 Datasheet, PDF (9/20 Pages) Microchip Technology – 50 mA, 100 mA and 150 mA CMOS LDOs with Shutdown and ERROR Output

TC1054/TC1055/TC1186
4.0 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 (DS21353)). Unlike bipolar regulators, the
TC1054, TC1055 and TC1186 supply current does not
increase with load current.
Figure 4-1 shows a typical application circuit, where 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 0.05 µA
(typical), V_OUT falls to zero volts, and ERROR is open-
circuited.
+
V_IN
V_OUT
+ ^{1 µF TC1054}
TC1055
Battery
TC1186
GND
V_OUT
+ _{1 µF}
C₁
Shutdown
SHDN ^ERROR
Control (to
CMOS Logic or
Tie to V_IN if
unused)
C₂ Required Only if
ERROR is used as a
Processor RESET
Signal (see Text)
V+
1R¹MΩ
BATTLOW
or RESET
0.2 µF
C₂
FIGURE 4-1:
Typical Application Circuit.
4.1 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
(typical) for a 5.0V regulator and 2.85V (typical) for a
3.0V regulator). ERROR output operation is shown in
Figure 4-2.
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 4-1, ERROR can be used either 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 ms 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).
V_OUT
V_TH
HYSTERESIS (V_H)
ERROR
V_IH
V_OL
FIGURE 4-2:
t_DELAY
Error Output Operation.
4.2 Output Capacitor
A 1 µF (minimum) capacitor from V_OUT to ground is
recommended. The output capacitor should have an
effective series resistance greater than 0.1 and less
than 10.0, with a resonant frequency above 1 MHz. A
1 µF 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.
 2002-2012 Microchip Technology Inc.
DS21350E-page 9