© 2005 Microchip Technology Inc. DS21435F-page 9
TC55
3.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1: PIN FUNCTION TABLE
3.1 Ground Terminal (GND)
Regulator ground. Tie GND to the negative side of the
output and the negative side of the input capacitor.
Only the LDO bias current (1 µA typical) flows out of
this pin, there is no high current. The LDO output regu-
lation is referenced to this pin. Minimize voltage drops
between this pin and the minus side of the load.
3.2 Regulated Voltage Output (V
OUT
)
Connect V
OUT
to the positive side of the load and the
positive terminal of the output capacitor. The positive
side of the output capacitor should be physically
located as close to the LDO V
OUT
pin as is practical.
The current flowing out of this pin is equal to the DC
load current.
3.3 Unregulated Supply Input (V
IN
)
Connect the input supply voltage and the positive side
of the input capacitor to V
IN
. The input capacitor should
be physically located as close as is practical to V
IN
. The
current flow into this pin is equal to the DC load current,
plus the LDO bias current (1 µA typical.)
4.0 DETAILED DESCRIPTION
The TC55 is a low quiescent current, precision, fixed-
output voltage LDO. Unlike bipolar regulators, the
TC55 supply current does not increase proportionally
with load current.
4.1 Output Capacitor
A minimum of 1 µF output capacitor is required. The
output capacitor should have an effective series resis-
tance (esr) greater than 0.1Ω and less than 5Ω, plus a
resonant frequency above 1 MHz. Larger output
capacitors can be used to improve supply noise rejec-
tion and transient response. Care should be taken
when increasing C
OUT
to ensure that the input imped-
ance is not high enough to cause high input impedance
oscillation.
4.2 Input Capacitor
A 1 µF input capacitor is recommended for most
applications when the input impedance is on the order
of 10Ω. Larger input capacitance may be required for
stability when operating off of a battery input, or if there
is a large distance from the input source to the LDO.
When large values of output capacitance are used, the
input capacitance should be increased to prevent high
source impedance oscillations.
Pin No. Symbol Description
1 GND Ground Terminal
2V
OUT
Regulated Voltage Output
3V
IN
Unregulated Supply Input
