© 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

positive terminal of the output capacitor. The positive

side of the output capacitor should be physically

The current flowing out of this pin is equal to the DC

load current.

3.3

Connect the input supply voltage and the positive side

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 0.1

Ω 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

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 10

Ω. 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

Regulated Voltage Output

Unregulated Supply Input