TC1073 datasheet(6/20 Pages) MICROCHIP

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TC1072/TC1073

DS21354B-page 6

3.0

DETAILED DESCRIPTION

The TC1072 and TC1073 are precision fixed output

voltage regulators. (If an adjustable version is desired,

please see the TC1070/TC1071/TC1187 data sheet.)

Unlike bipolar regulators, the TC1072 and TC1073’s

supply current does not increase with load current. In

addition, VOUT remains stable and within regulation

over the entire 0mA to IOUTMAX 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)isatorabove VIH, and shutdown (disabled)

when SHDN is at or below VIL. 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), VOUT falls to zero volts, and ERROR is open-

circuited.

FIGURE 3-1:

TYPICAL APPLICATION

CIRCUIT

3.1

ERROR Open Drain Output

ERROR is driven low whenever VOUT 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 output voltage

value (e.g. ERROR =VOL at 4.75V (typ.) for a 5.0V

regulator and 2.85V (typ.) for a 3.0V regulator).

ERROR output operation is shown in Figure 3-2.

Note that ERROR is active when VOUT falls to VTH,and

inactive when VOUT rises above VTH by VHYS.

As shown in Figure 3-1, ERROR canbeusedasa

battery low flag, or as a processor RESET signal (with

the addition of timing capacitor C2). R1 x C2 should be

chosen to maintain ERROR below VIH of the processor

RESET input for at least 200 msec to allow time for the

system to stabilize. Pull-up resistor R1 can be tied to

VOUT,VIN or any other voltage less than (VIN +0.3V).

FIGURE 3-2:

ERROR OUTPUT

OPERATION

3.2

Output Capacitor

µF(min) capacitor from VOUT to ground is

recommended. The output capacitor should have an

effective series resistance greater than 0.1

Ω and less

than 5.0

Ω, and a resonant frequency above 1MHz. A

µF capacitor should be connected from VIN 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 approxi-

mately -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

Bypass Input

A 470pF capacitor connected from the Bypass input to

ground

reduces

noise

present

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.

TC1072

TC1073

VOUT

SHDN

GND

ERROR

µF

VIN

VOUT

Shutdown Control

(to CMOS Logic or Tie

to VIN if unused)

µF

Battery

0.2

µF

C2 Required Only

if ERROR is used as a

Processor RESET Signal

(See Text)

V+

BATTLOW

or RESET

Bypass

C3, 470pF

VTH

VOUT

ERROR

VIH

VOL

HYSTERESIS (VH)

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