TC1274 Microchip Technology, TC1274 Datasheet - Page 6

• Manufacturer Part Number: TC1274
• Description: (TC1272 / TC1273 / TC1274) 3-Pin Reset Monitors for 5V Systems
• Manufacturer: Microchip Technology

TC1272/TC1273/TC1274
4.2
The TC1272/TC1273/TC1274 provides accurate V
monitoring and reset timing during power-up, power-
down and brownout/sag conditions, and rejects
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 condition.
Transient immunity can be improved by adding a
capacitor in close proximity to the V
TC1272/TC1273/TC1274.
4.3
The TC1272 RESET output is valid to V
Below this voltage the output becomes an "open
circuit" and does not sink current. This means CMOS
logic inputs to the P will be floating at an undeter-
mined voltage. Most digital systems are completely
shut down well above this voltage. However, in situa-
tions where RESET must be maintained valid to
V
RESET to ground to discharge stray capacitances and
hold the output low (Figure 4-6). This resistor value,
though not critical, should be chosen such that it does
not appreciably load RESET under normal operation
(100 k
larly, a pull-up resistor to V
TC1274 to ensure a valid high RESET for V
1.8V.
DS21382B-page 6
negative-going transients (glitches) on the power
supply line. Figure 4-5 shows the maximum transient
CC
= 0V, a pull-down resistor must be connected from
will be suitable for most applications). Simi-
V
RESET Signal Integrity During
Power-Down
CC
Transient Rejection
CC
is required for the
CC
CC
pin of the
CC
= 1.2V.
below
CC
FIGURE 4-5:
Duration vs. Overdrive For Glitch Rejection At
+25°C.
FIGURE 4-6:
V
cc
= 0V.
500
400
300
200
100
0
V
1
CC
RESET COMPARATOR OVERDRIVE,
TC1272
GND
V
V
CC
CC
RESET
10
Maximum Transient
Ensuring Reset Valid To
T
[V
A
Duration
CCTP
2003 Microchip Technology Inc.
= +25°C
-V
TC1272/3/4
CC
] (mV)
Overdrive
100
R
100 k
1
V
TH
1000