Obsolete Device
TC1275/TC1276/TC1277
3-Pin Reset Monitors for 3.3V Systems
Features
• Precision V
CC
Monitor for 3.3V Systems
• 100 ms Minimum RESET, RESET Output
Duration
• Output Valid to V
CC
= 1.2V
• V
CC
Transient Immunity
• Small 3-Pin SOT-23 Package
• No External Components
General Description
The TC1275/TC1276/TC1277 are cost-effective
system supervisor circuits designed to monitor V
CC
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 20 µs of V
CC
falling through the reset voltage threshold. RESET is
maintained active for a minimum of 100 ms after V
CC
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 V
CC
= 1.2V. The
TC1277 is valid down to V
CC
= 1.8V. All three devices
are available in a 3-Pin SOT-23 package.
Temp.
Range
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
Applications
•
•
•
•
Computers
Embedded Systems
Battery Powered Equipment
Critical µP Power Supply Monitoring
Device Selection Table
Part
Number
TC1275-xENB
TC1276-xENB
TC1277-xENB
Order
Complimentary
Open-Drain
Complimentary
Package
3-Pin SOT-23
3-Pin SOT-23
3-Pin SOT-23
The TC1275/TC1276/TC1277 devices are optimized to
reject fast transient glitches on the V
CC
line.
Typical Operating Circuit
VCC
2
VCC
1
RESET
VCC
Processor
RESET
Input
NOTE:
“x” denotes a suffix for V
CC
threshold (see table below).
Suffix
5
10
20
Reset V
CC
Threshold (V)
3.06
2.88
2.55
TC1275
GND
3
GND
Package Type
3-Pin SOT-23
RESET
*(RESET)
1
TC1275
TC1276
TC1277
V
CC
2
3
GND
*( ) is for TC1277
©
2007 Microchip Technology Inc.
DS21383C-page 1
TC1275/TC1276/TC1277
1.0
ELECTRICAL
CHARACTERISTICS
*Stresses above those listed under "Absolute Maximum
Ratings" may cause permanent damage to the device. These
are stress ratings only and functional operation of the device
at these or any other conditions above those indicated in the
operation sections of the specifications is not implied.
Exposure to Absolute Maximum Rating conditions for
extended periods may affect device reliability.
Absolute Maximum Ratings*
Supply Voltage (V
CC
to GND) .............................+6.0V
RESET, RESET.......................... -0.3V to (V
CC
+ 0.3V)
Input Current, V
CC
..............................................20 mA
Output Current, RESET, RESET ........................20 mA
Power Dissipation (T
A
≤
70°C)
3-Pin SOT-23 (derate 4 mW/°C above +70°C)
................................................................230 mW
Operating Temperature Range.............-40°C to +85°C
Storage Temperature Range ..............-65°C to +150°C
TC1275/TC1276/TC1277 ELECTRICAL SPECIFICATIONS
Recommended DC Operating Conditions:
T
A
= -40°C to +85°C unless otherwise noted. Typical values are at T
A
= +25°C.
Symbol
V
CC
Parameter
Supply Voltage
Min
1.2
1.8
Min
Typ
—
—
Typ
Max
5.5
5.5
Max
—
—
—
—
35
35
700
3.15
2.97
2.64
—
9.0
Max
300
50
50
—
—
300
300
V
V
V
pF
kΩ
Units
ms
µs
µs
µs
ns
ms
ms
TC1275, TC1276 V
CC(LOW)
= 1V,
Figure 3-2
TC1277
V
CC(LOW)
= 1V,
Figure 3-4
Figure 3-2, Figure 3-4
Figure 3-1, Figure 3-3
TC1275, TC1276 Note 4,
Figure 3-1
TC1277
Note 4,
Figure 3-3
TC1276
Test Conditions
mA
µA
—
—
—
2.98
2.80
2.47
—
3.0
Min
100
—
—
300
0
100
100
20
20
350
3.06
2.88
2.55
9
6.0
Typ
200
20
20
—
—
200
200
TC1275, TC1277
Note 3
Note 3
TC1276
Note 3
TC1276
Note 1
Note 1
Note 1
Units
V
Device
Test Conditions
TC1275, TC1276
Note 1
TC1277
Test Conditions
TC1275, TC1277
Note 1
TC1275
TC1277
Note 2
Note 2, Note 5
DC Electrical Characteristics:
T
A
= -40°C to +85°C unless otherwise noted. Typical values are at T
A
= +25°C.
Symbol
V
OH
I
OH
Parameter
Output Voltage @ 0-500μA
Output Current @ 2.4 Volts
V
CC
= 5V
V
CC
= 2.7V
Output Current @ 0.4 Volts
Operating Current
V
CC
< 5.5V
V
CCTP
< V
CC
< 5.5V
V
CC
< V
CCTP
V
CC
Trip Point (TC1275/6/7-5)
Units
V
mA
—
—
+10
13
1.3
30
V
CC
– 0.5V V
CC
– 0.1V
I
OL
I
CC
V
CCTP-5
V
CCTP-10
V
CC
Trip Point (TC1275/6/7-10)
V
CCTP-20
V
CC
Trip Point (TC1275/6/7-20)
C
OUT
R
P
Symbol
t
RST
t
RPD1
t
RPD2
t
F
t
R
t
RPU1
t
RPU2
Note
1:
2:
3:
4:
5:
Output Capacitance
Internal Pull-Up Resistor
Parameter
RESET Active Time
V
CC
Detect to RESET
V
CC
Detect to RESET
V
CC
Slew Rate
(V
CCTP
(MAX) to V
CCTP
(MIN))
V
CC
Slew Rate
(V
CCTP
(MIN) to V
CCTP
(MAX))
V
CC
Detect to RESET
V
CC
Detect to RESET
AC Electrical Characteristics:
T
A
= -40°C to +85°C unless otherwise noted. Typical values are at T
A
= +25°C.
All voltages referenced to ground.
Measured with V
CC
≥
2.7 volts.
Measured with RESET output open for TC1275/TC1276; measured with RESET output open for TC1277.
t
R
= 5 µs.
A 1 kΩ external resistor may be required in some applications for proper operation of the microprocessor reset control circuit when using
the TC1276.
DS21383C-page 2
©
2007 Microchip Technology Inc.
TC1275/TC1276/TC1277
2.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
Pin No.
(3-Pin SOT-23)
PIN FUNCTION TABLE
Symbol
Description
1
RESET
(TC1275/
TC1276)
RESET
RESET output remains low while V
CC
is below the reset voltage threshold, and
for 200 ms (100 ms minimum) after V
CC
rises above reset threshold. The output
stage of the TC1275 is complimentary. The output stage of the TC1276 is open-
drain.
RESET output remains high while V
CC
is below the reset voltage threshold, and
for 200 ms (100 ms minimum) after V
CC
rises above reset threshold. The output
stage of the TC1277 is complimentary.
Supply voltage (1.2V to 5.5V TC1275 and TC1276, 1.8V to 5.5V TC1277).
Ground.
1
(TC1277)
V
CC
GND
2
3
©
2007 Microchip Technology Inc.
DS21383C-page 3
TC1275/TC1276/TC1277
3.0
3.1
APPLICATIONS INFORMATION
Operation – Power Monitor
t
R
The TC1275/TC1276/TC1277 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 200 ms after
the power supply has reached the selected tolerance.
This allows the power supply and microprocessor to
stabilize before RESET is released.
V
CCTP
(MAX)
V
CCTP
(MIN)
V
CCTP
V
CC
t
RPU2
t
R
RESET
V
OL
V
CCTP
(MAX)
V
CCTP
(MIN)
V
CCTP
FIGURE 3-3:
Timing Diagram –
Power Up (TC1277).
t
F
V
CC
V
CC
t
RPU
1
V
CCTP
(MAX)
V
CCTP
V
OH
V
CCTP
(MIN)
RESET
FIGURE 3-1:
Timing Diagram – Power Up
(TC1275/TC1276).
t
F
V
CC
V
CCTP
(MAX)
V
CCTP
V
CCTP
(MIN)
RESET
V
OH
t
RPD2
RESET SLEWS WITH V
CC
FIGURE 3-4:
Timing Diagram –
Power Down (TC1277).
t
RPD1
RESET
V
OL
FIGURE 3-2:
Timing Diagram – Power
Down (TC1275/TC1276).
DS21383C-page 4
©
2007 Microchip Technology Inc.
TC1275/TC1276/TC1277
3.2
V
CC
Transient Rejection
The TC1275/TC1276/TC1277 provides accurate V
CC
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
CC
pin of the TC1275/TC1276/
TC1277.
V
CC
V
TH
Overdrive
Duration
MAXIMUM TRANSIENT DURATION (μsec)
500
T
A
400
°C
3.3
RESET Signal Integrity During
Power-Down
300
The TC1275 RESET output is valid to V
CC
= 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
V
CC
= 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
(100 kΩ will be suitable for most applications). Simi-
larly, a pull-up resistor to V
CC
is required for the
TC1277 to ensure a valid high RESET for V
CC
below
1.8V.
200
TC1275/6/7
100
0
1
10
1000
100
RESET COMPARATOR OVERDRIVE,
[
V
CCTP
- V
CC
]
(mV)
FIGURE 3-5:
Maximum Transient
Duration Vs. Overdrive For Glitch Rejection At
+25°C.
V
CC
V
CC
TC1275
RESET
R1
100k
GND
FIGURE 3-6:
TO V
CC
= 0V.
ENSURING RESET VALID
©
2007 Microchip Technology Inc.
DS21383C-page 5
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