TC1174 Microchip, TC1174 Datasheet - Page 4

• Manufacturer Part Number: TC1174
• Description: 300mA CMOS LDO with Shutdown and VREF Bypass
• Manufacturer: Microchip

TC1174
3.0
The TC1174 is an adjustable low drop-out regulator.
Unlike bipolar regulators, the TC1174’s supply current
does not increase with load current. In addition, V
remains stable and within regulation over the entire
0mA to I
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
when SHDN is at or below V
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
FIGURE 3-1:
DS21363B-page 4
V
OUT
470K
470K
R2
R1
DETAILED DESCRIPTION
OUT
OUT
+
MAX
C1
1µF
falls to zero.
operating load current range, (an
1
2
3
4
V
GND
NC
ADJ
OUT
TYPICAL APPLICATION
CIRCUIT
TC1174
IH
, and shutdown (disabled)
Bypass
SHDN
V
NC
IN
IL
8
7
6
5
. SHDN may be
Shutdown
Control
(from Power
Control Logic)
C
470pF
(Optional)
BYPASS
+
C2
1µF
Battery
OUT
+
–
3.1
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.
3.2
A 1µF (min) capacitor from V
The output capacitor should have an effective series
resistance greater than 0.1Ω and less than 5.0Ω. A 1µF
capacitor should be connected from V
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.
3.3
The output voltage setting is determined by the values
of R1 and R2 (Figure 3-1). The ohmic values of these
resistors should be between 470K and 3M to minimize
bleeder current.
The output voltage setting is calculated using the
following equation.
EQUATION 3-1:
The voltage adjustment range of the TC1174 is from
V
REF
to (V
Bypass Input
Output Capacitor
Adjust Input
IN
– 0.05V).
V
OUT
= V
REF
©
2002 Microchip Technology Inc.
x
OUT
[
R1
R2
to ground is required.
+ 1
IN
]
to GND if there