TC1107
DS21356C-page 4 2002-2012 Microchip Technology Inc.
3.0 DETAILED DESCRIPTION
The TC1107 is a precision regulator available in fixed
voltages. Unlike bipolar regulators, the TC1107’s
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 0.05A
(typical), V
OUT
falls to zero.
FIGURE 3-1: TYPICAL APPLICATION
CIRCUIT
3.1 Output Capacitor
A 1F (min) capacitor from V
OUT
to ground is required.
The output capacitor should have an effective series
resistance greater than 0.1 and less than 5.0. A 1F
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 Bypass Input
A 470pF capacitor connected from the Bypass input to
ground reduces noise present on the internal
reference, which in turn significantly reduces output
noise. If output noise is not a concern, this input may be
left unconnected. Larger capacitor values may be
used, but results in a longer time period to rated output
voltage when power is initially applied.
TC1107
1
2
3
4
5
6
7
8
V
OUT
V
OUT
C
BYPASS
Shutdown Control
(from Power Control Logic)
C2
1μF
GND
NC
Bypass
V
IN
NC
NC
SHDN
C1
1μF
Battery
+
++
–
470pF
(Optional)
