PRELIMINARY INFORMATION
50mA CMOS LDO WITH SHUTDOWN
AND ERROR OUTPUT
TC1054
Pull-up resistor R1 can be tied to VOUT, VIN or any other
voltage less than (VIN = 0.3V).
DETAILED DESCRIPTION
The TC1054 is a precision fixed output voltage regula-
tor. (If an adjustable version is desired, please see the
TC1070 or TC1071 data sheets.) Unlike the bipolar regula-
tors, the TC1054 supply current does not increase with load
current. In addition, VOUT remains stable and within regula-
tion at very low load currents (an important consideration in
RTC and CMOS RAM battery back-up applications).
Figure 1 shows a typical application circuit. The regula-
tor 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) and VOUT falls to zero volts and ERROR is open
circuited.
VOUT
HYSTERESIS (VHYS
)
VTH
ERROR
VIH
VOL
Figure 2. ERROR Output Operation
Output Capacitor
A 1µF(min) capacitor from VOUT to ground is recom-
mended. The output capacitor should have an effective
series resistance of 5Ω or less, 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 tanta-
lum capacitor types can be used. (Since many aluminum
electrolytic capacitors freeze at approximately – 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 tech-
niques.
V
V
V
OUT
OUT
IN
1µF
1µF
C1
BATTERY
GND
TC1054VCT
+
V
SHDN
ERROR
R1
1M
Shutdown Control
(to CMOS Logic or Tie
C2 Requires Only
if ERROR is used as a
Processor RESET Signal
(See Text)
BATTLOW
or RESET
to V if unused)
IN
0.2µF
C2
Figure 1. Typical Application Circuit
Thermal Considerations
ERROR Open Drain Output
Thermal Shutdown
ERROR is driven low whenever VOUT falls out of regu-
lation 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 4.75 (typ.) for a 5.0V regulator and
2.85V (typ.) for a 3.0V regulator). ERROR output operation
is shown in Figure 2.
Integrated thermal protection circuitry shuts the regula-
tor off when die temperature exceeds 160°C. The regulator
remains off until the die temperature drops to approximately
150°C.
Power Dissipation
The amount of power the regulator dissipates is prima-
rilyafunctionofinputandoutputvoltage,andoutputcurrent.
The following equation is used to calculate worst case
actual power dissipation:
Note that ERROR is active when VOUT falls to VTH, and
inactive when VOUT rises above VTH = VHYS
.
As shown in Figure 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 200msec to allow time for the system to stabilize.
TC1054-01 6/12/97
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