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TC1073-28VCH

50mA and 100mA CMOS LDOs with Shutdown, ERROR Output and VREF Bypass

Microchip Technology 

TC1072/TC1073

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) is at or above 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 0.05µA

(typical), VOUT falls to zero volts, and ERROR is open-

circuited.

FIGURE 3-1:

TYPICAL APPLICATION

CIRCUIT

+

1µF

+

Battery

VIN

VOUT

TC1072

TC1073

GND

Bypass

VOUT

+

1µF

C1

C3, 470pF

Shutdown Control

(to CMOS Logic or Tie

to VIN if unused)

SHDN ERROR

C2 Required Only

if ERROR is used as a

Processor RESET Signal

(See Text)

V+

R1

1M

0.2µF

C2

BATTLOW

or RESET

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 can be used as a

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:

VOUT

VTH

ERROR OUTPUT

OPERATION

HYSTERESIS (VH)

ERROR

VIH

VOL

3.2 Output Capacitor

A 1µF (min) capacitor from VOUT to ground is

recommended. The output capacitor should have an

effective series resistance greater than 0.1Ω and less

than 5.0Ω, and a resonant frequency above 1MHz. A

1µF 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 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.

DS21354B-page 6

© 2002 Microchip Technology Inc.

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