TC1275 MICROCHIP [Microchip Technology], TC1275 Datasheet - Page 5

• Manufacturer Part Number: TC1275
• Description: 3-Pin Reset Monitors for 3.3V Systems
• Manufacturer: MICROCHIP [Microchip Technology]

3.2
The TC1275/TC1276/TC1277 provides accurate V
monitoring and reset timing during power-up, power-
down, and brownout/sag conditions, and 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
TC1277.
3.3
The TC1275 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 µP 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
0V, a pull-down resistor must be connected from
RESET to ground to discharge stray capacitances and
hold the output low (Figure 3-6). This resistor value,
though not critical, should be chosen such that it does
not appreciably load RESET under normal operation
(100kΩ will be suitable for most applications). Similarly,
a pull-up resistor to V
ensure a valid high RESET for V
©
2002 Microchip Technology Inc.
V
RESET Signal Integrity During
Power-Down
CC
Transient Rejection
CC
CC
is required for the TC1277 to
pin of the TC1275/TC1276/
CC
below 1.8V.
CC
= 1.2V.
CC
CC
=
TC1275/TC1276/TC1277
FIGURE 3-5:
FIGURE 3-6:
500
400
300
200
100
0
1
V
CC
RESET COMPARATOR OVERDRIVE,
TC1275
V
GND
V
CC
[
10
CC
RESET
MAXIMUM TRANSIENT
DURATION VS.
OVERDRIVE FOR GLITCH
REJECTION AT 25°C
V
ENSURING RESET VALID
TO V
T
CCTP
A
Duration
CC
- V
TC1275/6/7
°C
CC
= 0V
]
100
Overdrive
(mV)
100k
R1
DS21383B-page 5
V
TH
1000