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TC1279-15ENBTR

P1-P3P4-P6P7-P9P10-P12
TC1278/TC1279
DS21384D-page 4 © 2007 Microchip Technology Inc.
2.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1: PIN FUNCTION TABLE
2.1 RESET (TC1279)
RESET output remains low while V
CC
is below the
reset voltage threshold, and for 350 ms (250 ms min.)
after V
CC
rises above reset threshold. The output stage
of the TC1279 is open-drain.
2.2 RESET (TC1278)
RESET output remains high while V
CC
is below the
reset voltage threshold, and for 350 ms (250 ms min.)
after V
CC
rises above reset threshold. The output stage
of the TC1278 is open-drain.
2.3 V
CC
Supply voltage (1.2V to 5.5V).
2.4 Ground
Device ground.
Pin No. Symbol Function
1 RESET
(TC1279)
RESET
output
1 RESET
(TC1278)
RESET output
2V
CC
Supply voltage (1.2V to 5.5V).
3 GND Ground.
© 2007 Microchip Technology Inc. DS21384D-page 5
TC1278/TC1279
3.0 APPLICATIONS INFORMATION
3.1 Operation – Power Monitor
The TC1278/TC1279 provide the function of detecting
out-of-tolerance power supply conditions and warning
a processor-based system of impending power failure.
When V
CC
is detected as out-of-tolerance, the RESET
signal is asserted. On power-up, RESET is kept active
for approximately 350 ms after the power supply has
reached the selected tolerance. This allows the power
supply and microprocessor to stabilize before RESET
is released.
FIGURE 3-1: TC1279 Power Up Timing
Diagram.
FIGURE 3-2: TC1279 Power-Down
Timing Diagram.
FIGURE 3-3: TC1278 Power-Up Timing
Diagram.
FIGURE 3-4: TC1278 Power-Down
Timing Diagram.
4.75V
4.00V
t
R
V
CCTP
V
CC
RESET
t
RPU1
V
OH
V
CC
RESET
4.75V
V
CCTP
4.00V
V
OL
t
RPD1
t
F
t
R
t
RPU2
V
OL
V
CCTP
V
CC
RESET
V
CCTP(MAX)
V
CCTP(MIN)
t
F
t
RPD2
V
CC
4.74V
V
OH
RESET
V
CCTP
4.00V
RESET SLEWS WITH V
CC
TC1278/TC1279
DS21384D-page 6 © 2007 Microchip Technology Inc.
3.2 V
CC
Transient Rejection
The TC1278/TC1279 provides accurate V
CC
monitor-
ing and reset timing during power-up, power-down,
and brownout/sag conditions. Furthermore, it rejects
negative-going transients (glitches) on the power
supply line. Figure 3-5 shows the maximum transient
duration vs. maximum negative excursion (overdrive)
for glitch rejection. Any combination of duration and
overdrive that lays under the curve will not generate a
reset signal. Combinations above the curve are
detected as a brownout or power-down. Transient
immunity can be improved by adding a capacitor in
close proximity to the V
CC
pin of the TC1278/TC1279.
FIGURE 3-5: Maximum Transient
Duration vs. Overdrive For Glitch Rejection At
+25°C.
RESET COMPARATOR OVERDRIVE,
[V
CCTP
- V
CC
] (mV)
5
3
2
4
1
0
1
5
100
1000
MAXIMUM TRANSIENT DURATION (µsec)
T
A
= +25°C
V
CCTP
Duration
Overdrive
V
CC
TC1278/9
P1-P3P4-P6P7-P9P10-P12

TC1279-15ENBTR

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IC RESET MONITOR 4.125V SOT23B-3
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