TC1275
TC1276
TC1277
3-PIN RESET MONITORS FOR 3.3V SYSTEMS
FEATURES
s
s
s
s
s
s
Precision V
CC
Monitor for 3.3V Systems
System Supplies
100 msec Guaranteed Minimum RESET, RESET
Output Duration
Output Guaranteed to V
CC
= 1.2V
V
CC
Transient Immunity
3-Pin SOT-23B Package
No External Components
GENERAL DESCRIPTION
The TC1275, TC1276 and 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
µsec
of V
CC
falling through the reset voltage threshold. Reset is main-
tained active for a minimum of 100msec 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. The TC1275 and TC1277 each
have a complimentary output while the TC1276 has an open
drain output. The output of the TC1275 and TC1276 is
guaranteed valid down to V
CC
= 1.2V. The TC1277 is
guaranteed valid down to V
CC
= 1.8V. All three devices are
available in a 3-Pin SOT-23B package.
The TC1275/6/7 are optimized to reject fast transient
glitches on the V
CC
line.
TYPICAL APPLICATIONS
s
s
s
s
Computers
Embedded Systems
Battery Powered Equipment
Critical
µ
P Power Supply Monitoring
TYPICAL OPERATING CIRCUIT
V
CC
2
V
CC
1
V
CC
PROCESSOR
RESET
INPUT
GND
ORDERING INFORMATION
Part No.
TC1275-xENB
TC1276-xENB
TC1277-xENB
Order
Complimentary
Open Drain
Complimentary
Package
Temp. Range
RESET
TC1275
GND
3
3-Pin SOT-23B – 40°C to +85°C
3-Pin SOT-23B – 40°C to +85°C
3-Pin SOT-23B – 40°C to +85°C
NOTE: The "x" denotes a suffix for V
CC
threshold - see table below.
Suffix
PIN CONFIGURATION
*3-Pin SOT-23B
5
10
20
Reset V
CC
Threshold (V)
3.06
2.88
2.55
RESET **(RESET)
1
TC1275-xENB
TC1276-xENB
TC1277-xENB
3
GND
VCC
2
NOTES: *3-Pin SOT-23B is equivalent to JEDEC TO-236
** () is for TC1277
TC1275/6/7-1 9/9/99 TelCom reserves the right to make changes in the circuitry and specifications of its devices.
3-PIN MONITORS FOR 3.3V SYSTEMS
TC1275
TC1276
TC1277
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage (V
CC
to GND)................................... +6.0V
RESET, RESET ............................ – 0.3V to (V
CC
+ 0.3V)
Input Current, V
CC
.....................................................20mA
Output Current, RESET, RESET .............................20mA
Operating Temperature Range ............... – 40°C to +85°C
Power Dissipation (T
A
≤
70°C)
3-Pin SOT-23B (derate 4mW/°C above +70°C)......230mW
Storage Temperature Range ................ – 65°C to +150°C
Lead Temperature (Soldering, 10 sec) ................. +260°C
*This is a stress rating only and functional operation of the device at these
or any other conditions above those indicated in the operational sections of
the specifications is not implied. Exposure to Absolute Maximum Rating
Conditions for extended periods may affect device reliability.
RECOMMENDED DC OPERATING CONDITIONS:
T
A
= -40°C to + 85°C unless otherwise specified.
Typical values apply at T
A
=+25°C.
Symbol Parameter
V
CC
Test Conditions
Min
1.2
1.8
Typ
—
—
Max
5.5
5.5
Unit
V
V
Supply Voltage(TC1275, TC1276) (note 1)
(TC1277)
Typical values apply at T
A
=+25°C.
DC ELECTRICAL CHARACTERISTICS:
T
A
= -40°C to + 85°C unless otherwise specified.
Symbol
V
OH
I
OH
Parameter
Output Voltage @ 0-500
µA
(TC1275, TC1277)
Output Current @2.4 volts
V
CC
= 5V (TC1275)
V
CC
= 2.7V (TC1277)
Output Current @0.4 volts
Operating Current
V
CC
<5.5V (TC1275, TC1277)
V
CCTP
< V
CC
< 5.5V (TC1276)
V
CC
<V
CCTP
(TC1276)
V
CC
Trip Point (TC1275/6/7-5)
V
CC
Trip Point (TC1275/6/7-10)
V
CC
Trip Point (TC1275/6/7-20)
Output Capacitance
Test Conditions
(note 1)
Min
Typ
Max
—
Unit
V
V
CC
-0.5V V
CC
-0.1V
(note 2)
(notes 2,5)
(note 3)
(note 3)
(note 3)
(note 1)
(note 1)
(note 1)
I
OL
I
CC
—
—
+10
—
—
—
2.98
2.80
2.47
—
3.0
13
1.3
30
20
20
350
3.06
2.88
2.55
9
6.0
—
—
—
35
35
700
3.15
2.97
2.64
—
9.0
mA
mA
mA
µA
µA
µA
V
V
V
pF
kΩ
V
CCTP
-
5
V
CCTP
-
10
V
CCTP
-
20
C
OUT
R
P
Internal Pull-Up Resistor (TC1276)
Typical values apply at T
A
=+25°C.
AC ELECTRICAL CHARACTERISTICS:
T
A
= -40°C to + 85°C unless otherwise specified.
Symbol
t
RST
t
RPD1
t
RPD2
t
F
t
R
t
RPU1
t
RPU2
NOTES:
Parameter
RESET Active Time
V
CC
Detect to RESET
(TC1275, TC1276)
V
CC
Detect to RESET
(TC1277)
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
(TC1275, TC1276)
V
CC
Detect to RESET
(TC1277)
Test Conditions
V
CC(LOW)
= 1V(figure 2)
V
CC(LOW)
= 1V(figure 4)
(figures 2, 4)
(figures 1, 3)
(note 4, figure 1)
(note 4, figure 3)
Min
100
—
—
300
0
100
100
Typ
200
20
20
—
—
200
200
Max
300
50
50
—
—
300
300
Unit
ms
µs
µs
µs
ns
ms
ms
1. All voltages are referenced to ground.
2. Measured with V
CC
≥
2.7 volts.
3. Measured with RESET output open for TC1275/6; measured with RESET output open for TC1277.
4. t
R
= 5
µs.
5. A 1kΩ external resistor may be required in some applications for proper operation of the microprocessor reset control circuit
when using the TC1276.
2
TC1275/6/7-1 9/9/99
3-PIN MONITORS FOR 3.3V SYSTEMS
TC1275
TC1276
TC1277
PIN DESCRIPTION
Pin No.
(3-Pin SOT-23B)
1
Symbol
RESET
(TC1275, TC1276)
Description
RESET output remains low while V
CC
is below the reset voltage threshold, and
for 200msec (100msec min.) 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 200msec (100msec min.) after V
CC
rises above reset threshold. The
ouput stage of the TC1277 is complimentary.
Supply voltage (1.2V to 5.5V TC1275/76, 1.8 to 5.5V TC1277)
Ground
1
RESET
(TC1277)
V
CC
GND
2
3
APPLICATION INFORMATION
Operation - Power Monitor
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
t
R
V
CCTP(MAX)
V
CCTP(MIN)
V
CC
t
RPU
1
V
OH
RESET
Figure 1. Timing Diagram: Power Up (TC1275, TC1276)
t
F
V
CC
V
CCTP
(MAX)
V
CCTP
V
CCTP
(MIN)
t
R
V
CCTP(MAX)
V
CCTP(MIN)
V
CCTP
t
RPD1
RESET
VCC
t
RPU
2
V
OL
RESET
V
OL
Figure 2. Timing Diagram: Power Down (TC1275, TC1276)
Figure 3. Timing Diagram: Power Up (TC1277)
TC1275/6/7-1
9/9/99
3
3-PIN MONITORS FOR 3.3V SYSTEMS
TC1275
TC1276
TC1277
V
CC
Transient Rejection
t
F
V
CC
V
CCTP(MAX)
V
CCTP
V
CCTP(MIN)
t
RPD2
The TC1275/6/7 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 5 shows the maximum transient
duration vs. maximum negative excursion (overdrive) for glitch
rejection. Any combination of duration and overdrive which lies
under
the curve will
not
generate a reset signal. Combina-
tions 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 TC1275/6/7.
V
CC
V
OH
RESET SLEWS WITH V
CC
RESET
V
CC
TC1275
RESET
Figure 4. Timing Diagram: Power Down (TC1277)
V
CC
GND
R1
100k
V
TH
Overdrive
Figure 6. Ensuring RESET Valid to V
CC
= 0V
Duration
MAXIMUM TRANSIENT DURATION (µsec)
500
T
A
= +25°C
400
RESET Signal Integrity During Power-Down
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 undetermined voltage. Most
digital systems are completely shutdown well above this
voltage. However, in situations 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 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
CC
is required for the
TC1277 to ensure a valid high RESET for V
CC
below 1.8V.
300
200
TC1275/6/7
100
0
1
10
1000
100
RESET COMPARATOR OVERDRIVE,
[
VCCTP - VCC
]
(mV)
Figure 5. Maximum Transient Duration vs.
Overdrive for Glitch Rejection at 25
°
C
TC1275/6/7-1 9/9/99
4
3-PIN MONITORS FOR 3.3V SYSTEMS
TC1275
TC1276
TC1277
TYPICAL CHARACTERISTICS
V
CC
DETECT TO RESET (RESET)
T
A
= 25°C
300
RESET DELAYS vs.
COMPARATOR OVERDRIVE
T
A
= 25°C
V
CC
TO RESET DELAY (µsec)
100000
V
OD
= 20mV
V
OD
= 100mV
V
OD
= 200mV
V
OD
= 1V
V
OD
= 2V
V
CC
TO RESET DELAY (µsec)
200
10000
1000
100
100
10
0
1
10
100
1000
10000
100000
0
1
2
3
4
5
V
CC
SLEW RATE (V/µsec)
Figure 7
COMPARATOR OVERDRIVE (V)
Figure 8
MARKINGS
PART NUMBERS AND PART MARKINGS
3-Pin SOT-23B
&
= part number code + temperature range and voltage
TC1275 (V)
2.55
2.88
3.06
TC1276 (V)
2.55
2.88
3.06
TC1277 (V)
2.55
2.88
3.06
D A
ex: 1275-20=
kkkk
Code
DA
DB
DC
Code
EA
EB
EC
Code
FA
FB
FC
represents year and quarter code
represents lot ID number
TC1275/6/7-1
9/9/99
5
Microcontroller MCU
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