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TC1054

50 mA, 100 mA and 150 mA CMOS LDOs with Shutdown and ERROR Output

Microchip Technology 

TC1054/TC1055/TC1186

4.0 DETAILED DESCRIPTION

The TC1054, TC1055 and TC1186 are precision fixed

output voltage regulators (If an adjustable version is

desired, please see the TC1070/TC1071/TC1187 data

sheet (DS21353)). Unlike bipolar regulators, the

TC1054, TC1055 and TC1186 supply current does not

increase with load current.

Figure 4-1 shows a typical application circuit, where 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 0.05 µA

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

circuited.

+

VIN

VOUT

+

1 µF TC1054

TC1055

Battery

TC1186

GND

VOUT

+1 µF

C1

SHDN ERROR

Shutdown Control

(to CMOS Logic or Tie

to VIN if unused)

C2 Required Only

if ERROR is used as a

Processor RESET Signal

(See Text)

V+

R1

1MW

BATTLOW

or RESET

0.2 µF

C2

FIGURE 4-1:

Typical Application Circuit.

4.1 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 threshold is 5%

below rated VOUT, regardless of the programmed

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 4-2.

Note that ERROR is active when VOUT falls to VTH and

inactive when VOUT rises above VTH by VHYS.

As shown in Figure 4-1, ERROR can be used either 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 ms 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).

VOUT

VTH

HYSTERESIS (VH)

ERROR

VIH

VOL

FIGURE 4-2:

tDELAY

Error Output Operation.

4.2 Output Capacitor

A 1 µF (minimum) 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, with a resonant frequency above 1 MHz. A

1 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.

© 2007 Microchip Technology Inc.

DS21350D-page 9

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