© 2009 Microchip Technology Inc. DS21663D-page 11
TC2054/2055/2186
4.0 DETAILED DESCRIPTION
The TC2054, TC2055 and TC2186 are precision fixed
output voltage regulators. (If an adjustable version is
desired, refer to the TC1070/TC1071/TC1187 data
sheet (DS21353). Unlike bipolar regulators, the
TC2054, TC2055 and TC2186 supply current does not
increase with load current. In addition, V
OUT
remains
stable and within regulation over the entire 0 mA to
maximum output current operating load range.
Figure 4-1 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 0.05 µA
(typical), V
OUT
falls to zero volts, and ERROR is
open-circuited.
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 as a
battery low flag or as a processor RESET
signal (with
the addition of timing capacitor C
2
). R
1
x C
2
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 R
1
can be tied to
V
OUT
, V
IN
or any other voltage less than (V
IN
+ 0.3V).
The ERROR
pin sink current is self-limiting to
approximately 18 mA.
FIGURE 4-2: Error Output Operation.
4.2 Output Capacitor
A 1 µF (minimum) capacitor from V
OUT
to ground is
required. The output capacitor should have an effective
series resistance of 0.01Ω. to 5Ω for V
OUT
= 2.5V, and
0.05Ω. to 5Ω for V
OUT
< 2.5V. Ceramic, tantalum and
aluminum electrolytic capacitors 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.
4.3 Input Capacitor
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 this AC filter capacitor, or if a battery is
used as the power source. Aluminum electrolytic or
tantalum capacitors can be used (since many
aluminum electrolytic capacitors freeze at
approximately -30°C, solid tantalum 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.
0.2 µF
C
2
R
1
1MΩ
V+
C2 Required Only
if ERROR
is used as a
Processor RESET
Signal
(See Text)
Shutdown Control
(to CMOS Logic or Tie
to V
IN
if unused)
BATTLOW
or RESET
TC2054
TC2055
TC2186
V
IN
BATTERY
V
OUT
GND
1µF
V
OUT
1µF
C
1
ERRORSHDN
V
IH
V
OL
ERROR
V
TH
V
OUT
HYSTERESIS (V
HYS
)
