TC1277 Datasheet PDF - Microchip Technology
| Part Number | TC1277 | |
| Description | (TC1275 / TC1276 / TC1277) 3-Pin Reset Monitors for 3.3V Systems | |
| Manufacturers | Microchip Technology | |
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TC1275/TC1276/TC1277
3-Pin Reset Monitors for 3.3V Systems
Features
• Precision VCC Monitor for 3.3V Systems
• 100msec Minimum RESET, RESET Output
Duration
• Output Valid to VCC = 1.2V
• VCC Transient Immunity
• Small 3-Pin SOT-23B Package
• No External Components
Applications
• Computers
• Embedded Systems
• Battery Powered Equipment
• Critical µP Power Supply Monitoring
Device Selection Table
Part
Number
Order
Package
Temp.
Range
TC1275-xENB Complimentary 3-Pin SOT-23B -40°C to +85°C
TC1276-xENB Open Drain 3-Pin SOT-23B -40°C to +85°C
TC1277-xENB Complimentary 3-Pin SOT-23B -40°C to +85°C
NOTE: “x” denotes a suffix for VCC threshold (see table below).
Suffix
5
10
20
Package Type
Reset VCC Threshold (V)
3.06
2.88
2.55
3-Pin SOT-23B
General Description
The TC1275/TC1276/TC1277 are cost-effective
system supervisor circuits designed to monitor VCC in
digital systems and provide a reset signal to the host
processor when necessary. No external components
are required.
The reset output is driven active within 20µsec of VCC
falling through the reset voltage threshold. RESET is
maintained active for a minimum of 100msec after VCC
rises above the reset threshold. The TC1277 has an
active-high RESET output while the TC1275 and
TC1276 have an active-low RESET output. TC1275
and TC1277 each have a complimentary output while
the TC1276 has an open drain output. The output of the
TC1275 and TC1276 is valid down to VCC = 1.2V. The
TC1277 is valid down to VCC = 1.8V. All three devices
are available in a 3-Pin SOT-23B package.
The TC1275/TC1276/TC1277 devices are optimized to
reject fast transient glitches on the VCC line.
Typical Operating Circuit
VCC
2
VCC
1
RESET
VCC
Processor
RESET
Input
TC1275
GND
3
GND
RESET 1
*(RESET)
TC1275-xENB
TC1276-xENB 3 GND
TC1277-xENB
VCC 2
NOTE: 3-Pin SOT-23B is equivalent to JEDEC TO-236
*( ) is for TC1277
© 2002 Microchip Technology Inc.
DS21383B-page 1
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TC1275/TC1276/TC1277
3.2 VCC Transient Rejection
The TC1275/TC1276/TC1277 provides accurate VCC
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 VCC pin of the TC1275/TC1276/
TC1277.
3.3 RESET Signal Integrity During
Power-Down
The TC1275 RESET output is valid to VCC = 1.2V.
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 VCC =
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 VCC is required for the TC1277 to
ensure a valid high RESET for VCC below 1.8V.
FIGURE 3-5:
VCC
MAXIMUM TRANSIENT
DURATION VS.
OVERDRIVE FOR GLITCH
REJECTION AT 25°C
VTH
Overdrive
Duration
500
TA °C
400
300
200
100 TC1275/6/7
0
1 10 100 1000
RESET COMPARATOR OVERDRIVE,
[VCCTP - VCC] (mV)
FIGURE 3-6:
ENSURING RESET VALID
TO VCC = 0V
VCC
VCC
TC1275
RESET
GND
R1
100k
© 2002 Microchip Technology Inc.
DS21383B-page 5
Preview 5 Page |
Part DetailsOn this page, you can learn information such as the schematic, equivalent, pinout, replacement, circuit, and manual for TC1277 electronic component. |
| Information | Total 13 Pages | |
| Link URL | [ Copy URL to Clipboard ] | |
| Download | [ TC1277.PDF Datasheet ] | |
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