19-2243; Rev 1;
12/05
Low-Power μP Reset Circuits in 3-Pin
SC70/SOT23
MXD1810–MXD1813/MXD1815–MXD1818*
General Description
The MXD1810–MXD1813/MXD1815–MXD1818 family of
microprocessor (μP) reset circuits monitor power sup-
plies in μP and digital systems. These devices provide
excellent circuit reliability and low cost by eliminating
external components and adjustments when used with
+2.5V/+3.0V/+3.3V (MXD1815–MXD1818), and +5V
(MXD1810–MXD1813) systems.
These circuits assert a reset signal whenever the V
CC
supply voltage declines below a preset threshold,
keeping reset asserted for at least 100ms after V
CC
rises above the reset threshold. The MXD1813/
MXD1818 also keep reset asserted for at least 100ms
after the output is momentarily pulled to GND by an
external push-button switch.
The MXD1812/MXD1817 have an active-high push-pull
RESET output. The MXD1810/MXD1815 (push-pull) and
MXD1811/MXD1813/MXD1816/MD1818 (open-drain)
have an active-low
RESET
output. The open-drain
devices (MXD1811/MXD1813/MXD1816/MXD1818)
have an internal pullup resistor to V
CC
. The MXD1813/
MXD1818 feature a debounced manual reset feature
that asserts a reset if the
RESET
pin is pulled low for
more than 1.5μs. When used to initiate manual reset,
RESET
debounces signals from devices such as
mechanical switches. For devices with this feature, the
release of the external switch triggers the reset period.
The MXD1810–MXD1813/MXD1815–MXD1818 are
guaranteed to output the correct logic state for V
CC
down to +1V. These ICs provide a reset comparator
designed to ignore fast transients on V
CC
. Reset
thresholds are available between +2.18V and +4.62V.
These small, low-power (4μA) devices are ideal for use
in portable equipment. All are available in space-saving
3-pin SC70 and SOT23 packages, and are specified
from -40°C to +105°C.
Features
o
Precision Monitoring of +2.5V, +3V, +3.3V, and
+5V Power-Supply Voltages
o
Available in Four Reset Output Configurations
o
Factory-Set Reset Threshold Voltages: 2.18V,
2.31V, 2.55V, 2.88V, 3.06V, 4.12V, 4.37V, 4.62V
o
±2.5% Reset Threshold Accuracy Over
Temperature
o
Fixed Reset Timeout Period: 100ms (min)
o
Guaranteed RESET/RESET Valid to V
CC
= +1V
o
Debounced Manual Reset
Detect (MXD1813/MXD1818)
o
Power-Supply Transient Immunity
o
No External Components
o
Low Power Consumption (4μA)
o
Pin Compatible with DS181_ Products (SOT23)
o
3-Pin SC70 and SOT23 Packages
Ordering Information
PART
†
MXD1810UR_
_-T
MXD1810XR_ _-T
†
The
TEMP RANGE
-40 C to +105 C
-40
o
C to +105
o
C
o
o
PIN-PACKAGE
3 SOT23-3
3 SC70-3
MXD1810–MXD1813/MXD1815–MXD1818 are available
with factory-set V
CC
reset thresholds from +2.18V to +3.06V
(MXD1815–MXD1818) and +4.12V to +4.62V (MXD1810–
MXD1813). Choose the desired reset-threshold suffix from the
Reset Threshold Table and insert it in place of the “_ _” follow-
ing “R” in the part number. All devices are available in tape-
and-reel only in 2500 unit increments. Other threshold
voltages may be available. Contact factory for availability.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
Ordering Information continued at end of data sheet.
Applications
Computers and Controllers
Intelligent Instruments
Set-Top Boxes
Printers
Automotive Systems
Critical μP and μC Monitoring
Portable/Battery-Powered Equipment
Pin Configurations
TOP VIEW
V
CC
1
RESET
1
(RESET)
MXD181_X
RESET
2
(RESET)
3
GND
V
CC
2
MXD181_U
3
GND
SC70-3
SOT23-3
() ARE FOR THE MXD1812/MXD1817
*Patent
pending
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Low-Power μP Reset Circuits in 3-Pin
SC70/SOT23
MXD1810–MXD1813/MXD1815–MXD1818
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ...........................................................-0.3V to +6.0V
Push-Pull
RESET
(MXD1810/MXD1815),
RESET (MXD1812/MXD1817) to GND.....-0.3V to (V
CC
+ 0.3V)
Open-Drain
RESET
(MXD1811/MXD1816)
to GND................................................................-0.3V to +6.0V
Open-Drain
RESET
(MXD1813/MXD1818)
to GND ....................................................-0.3V to (V
CC
+ 0.3V)
Input Current (V
CC
,
RESET)
................................................20mA
Output Current (RESET, RESET).........................................20mA
Continuous Power Dissipation (T
A
= +70°C)
3-Pin SC70 (derate 2.17mW above +70°C) ..................174mW
3-Pin SOT23 (derate 4mW/°C above +70°C) ...............320mW
Operating Temperature Range .........................-40°C to +105°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond 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 beyond 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.
ELECTRICAL CHARACTERISTICS
(V
CC
= full range, T
A
= -40°C to +105°C, unless otherwise specified. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Supply Voltage Range
Supply Current
SYMBOL
V
CC
I
CC
CONDITIONS
T
A
= 0°C to +105°C
T
A
= -40°C to +105°C
V
CC
= +5.5V, V
CC
> V
TH
, no load
V
CC
= +3.6V, V
CC
> V
TH
, no load
MXD181_ _ R46
MXD181_ _ R44
MXD181_ _ R41
Reset Threshold
V
TH
MXD181_ _ R31
MXD181_ _ R29
MXD181_ _ R26
MXD181_ _ R23
MXD181_ _ R22
Active Reset Timeout Period
V
CC
to Reset Delay
Push-Button Detect to Reset
Push-Button Reset Timeout Period
Input Low Voltage
Input High Voltage
RESET
Output Source Current
RESET Output Source Current
t
RP
t
RD
t
PB
t
PBRST
V
IL
V
IH
I
OH
I
OH
V
CC
rising
V
CC
= (V
TH
+ 100mV) falling to (V
TH
- 200mV)
V
CC
rising, t
R
= 5μs
MXD1813/MXD1818 only
MXD1813/MXD1818 only
MXD1813/MXD1818
only
T
A
= +25°C to +105°C
T
A
= -40°C to +25°C
0.7
×
V
CC
350
350
100
1.5
100
150
250
0.34
0.15
4.50
4.25
4.00
2.98
2.80
2.47
2.25
2.12
100
MIN
1.0
1.2
9
4
4.62
4.37
4.12
3.06
2.88
2.55
2.31
2.18
150
2
150
TYP
MAX
5.5
5.5
16
10
4.75
4.49
4.24
3.15
2.97
2.64
2.37
2.25
250
5
250
ms
μs
ms
μs
ms
V
V
μA
μA
V
UNITS
V
μA
MXD1813/MXD1818 only
V
CC
≥
V
TH(MAX)
, reset not asserted,
MXD1810/MXD1815
V
CC
≤
V
TH(MIN)
, reset asserted,
MXD1812/MXD1817
V
CC
≥
2.7V, reset asserted, V
OUT
= 0.4V
MXD1810/MXD1811/MXD1813/MXD1815/
MXD1816/MXD1818
(Note 2)
V
CC
≥
2.7V, reset not asserted, , V
OUT
= 0.4V
MXD1812/MXD1817
RESET
Output Sink Current
I
OL
10
mA
RESET Output Sink Current
I
OL
10
mA
2
_______________________________________________________________________________________
Low-Power μP Reset Circuits in 3-Pin
SC70/SOT23
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= full range, T
A
= -40°C to +105°C, unless otherwise specified. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Output High Voltage
Output Capacitance (Note 2)
Internal Pullup Resistor
Open-Drain
SYMBOL
V
OH
C
OUT
R
P
MXD1811/MXD1816
MXD1813/MXD1818
3.5
3.1
5.5
5.5
CONDITIONS
0 < I
OH
< 500μA
MIN
V
CC
-
0.5
TYP
V
CC
-
0.1
10
7.5
7.5
MAX
UNITS
V
pF
kΩ
MXD1810–MXD1813/MXD1815–MXD1818
Note 1:
Production testing done at T
A
= +25°C; limits over temperature guaranteed by design.
Note 2:
The MXD1811/MXD1813/MXD1816/MXD1818 have an internal pullup resistor which may deliver 1mA of sink current.
Note 3:
Guaranteed by design.
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
MXD1810-13/15-18 toc01
RESET TIMEOUT PERIOD
vs. TEMPERATURE (V
CC
RISING)
MXD1810-13/15-18 toc02
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE (V
CC
FALLING)
MXD1810-13/15-18 toc03
10
RESET/RESET NOT ASSERTED
8
SUPPLY CURRENT (μA)
V
CC
= +5V
1.010
NORMALIZED RESET THRESHOLD
160
TIMEOUT PERIOD (ms)
156
152
148
144
140
V
CC
= +2.5V
V
CC
= +5V
1.005
V
TH
= +4.62V
1.000
V
TH
= +2.18V
0.995
6
4
V
CC
= +3.3V
2
V
CC
= +2.5V
0
-40
-10
20
50
80
110
TEMPERATURE (°C)
0.990
-40
-10
20
50
80
110
-40
-10
20
50
80
110
TEMPERATURE (°C)
TEMPERATURE (°C)
POWER-DOWN RESET DELAY
vs. TEMPERATURE
MXD1810-13/15-18 toc04
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
MXD1810-13/15 toc05
OUTPUT VOLTAGE
vs. OUTPUT SINK CURRENT
MXD1810-13/15-18 toc06
3.0
POWER-DOWN RESET DELAY (μs)
2.5
V
TH
= +4.62V
2.0
1.5
1.0
0.5
0
-40
-10
20
50
80
110
TEMPERATURE (°C)
100
MAXIMUM TRANSIENT DURATION (μs)
90
80
70
60
50
40
30
20
10
0
RESET OCCURS
ABOVE THIS LINE
200
160
OUTPUT VOLTAGE (mV)
120
80
V
TH
= +2.18V
40
0
10
100
1000
RESET THRESHOLD OVERDRIVE, V
TH
- V
CC
(mV)
0
3
6
9
12
15
OUTPUT CURRENT (mA)
_______________________________________________________________________________________
3
Low-Power μP Reset Circuits in 3-Pin
SC70/SOT23
MXD1810–MXD1813/MXD1815–MXD1818
Typical Operating Characteristics (continued)
(T
A
= +25°C, unless otherwise noted.)
OUTPUT VOLTAGE
vs. OUTPUT SOURCE CURRENT
MXD1810-13/15-18 toc07
INPUT LOW VOLTAGE
vs. V
CC
AND TEMPERATURE
MXD1810-13/15 toc08
0.5
0.8
INPUT LOW VOLTAGE (V)
0.4
V
CC
- V
OUT
(V)
V
CC
= +5.5V
0.6
0.3
0.2
0.4
V
CC
= +2.2V
0.1
0
0
0.5
1.0
1.5
2.0
2.5
3.0
OUTPUT CURRENT (mA)
0.2
-40
-10
20
50
80
110
TEMPERATURE (°C)
Pin Descriptions
MXD1810/MXD1815
PIN
SC70
2
1
3
SOT23
1
2
3
RESET
V
CC
GND
Push-Pull, Active-Low Reset Output.
RESET
changes from high to low when V
CC
drops
below the selected reset threshold.
RESET
remains low for the reset timeout period after
VCC exceeds the device reset threshold.
Supply Voltage and Input for Reset Threshold Monitor
Ground
NAME
FUNCTION
MXD1811/MXD1816
PIN
SC70
2
1
3
SOT23
1
2
3
NAME
FUNCTION
Open-Drain, Active-Low Reset Output.
RESET
changes from high to low when V
CC
drops
below the selected reset threshold.
RESET
remains low for the reset timeout period after
V
CC
exceeds the device reset threshold.
RESET
has an internal 5.5kΩ pullup resistor.
Supply Voltage and Input for Reset Threshold Monitor
Ground
RESET
V
CC
GND
4
_______________________________________________________________________________________
Low-Power μP Reset Circuits in 3-Pin
SC70/SOT23
Pin Descriptions (continued)
MXD1812/MXD1817
PIN
SC70
2
1
3
SOT23
1
2
3
NAME
FUNCTION
Push-Pull, Active-High Reset Output. RESET changes from low to high when V
CC
drops
below the selected reset threshold. RESET remains high for the reset timeout period after
V
CC
exceeds the device reset threshold.
Supply Voltage and Input for Reset Threshold Monitor
Ground
MXD1810–MXD1813/MXD1815–MXD1818
RESET
V
CC
GND
MXD1813/MXD1818
PIN
SC70
SOT23
NAME
FUNCTION
Open-Drain, Active-Low Reset Output with Manual Reset Detect.
RESET
changes from
high to low when V
CC
drops below the selected reset threshold, or
RESET
is externally
pulled low for at least 1.5μs.
RESET
remains low for the reset timeout period after V
CC
exceeds the device reset threshold or after the external manual reset is released.
RESET
has an internal 5.5kΩ pullup resistor.
Supply Voltage and Input for Reset Threshold Monitor
Ground
2
1
RESET
1
3
2
3
V
CC
GND
Detailed Description
RESET
/RESET Output
A microprocessor’s (μP’s) reset input starts the micro-
processor in a known state. The MXD1810–MXD1813/
MXD1815–MXD1818 μP supervisory circuits assert
reset to prevent code-execution errors during power-
up, power-down, and brownout conditions (Figure 4).
Whenever V
CC
falls below the reset threshold, the reset
output asserts. Once V
CC
exceeds the reset threshold,
an internal timer keeps the reset output asserted for the
specified reset timeout period (t
RP
). Reset is also trig-
gered by an externally initiated rising edge on the
RESET
pin (MXD1813/MXD1818), following a low signal
of 1.5μs minimum duration.
(t
PBRST
). A manual reset input shorter than 1.5μs may
release
RESET
without the 100ms minimum reset time-
out delay. To facilitate use with mechanical switches,
the MXD1813/MXD1818 contain internal debouncing
circuitry. A debounced waveform is shown in Figure 6.
Applications Information
Since the
RESET
output on the MXD1811/MXD1816 is
open drain, these devices interface easily with μPs that
have bidirectional reset pins, such as the Motorola
68HC11. Connecting the μP supervisor’s
RESET
output
directly to the microcontroller’s (μC’s)
RESET
pin allows
either device to assert reset (Figure 7). No external
pullup resistor is required, as it is contained within the
MXD1811/MXD1816.
Interfacing to μPs with Bidirectional
Reset Pins
Push-Button Reset (MXD1813/MXD1818)
Many μP-based products require push-button reset
capability (Figure 5), allowing the operator, a test tech-
nician, or external logic circuitry to initiate reset. On the
MXD1813/MXD1818, a logic-low on
RESET
held for
greater than 1.5μs asserts a reset.
RESET
deasserts
following a 100ms minimum reset timeout delay
Negative-Going V
CC
Transients
In addition to issuing a reset to the μP during power-up,
power-down, and brownout conditions, these devices
are relatively immune to short-duration, negative-going
V
CC
transients (glitches).
5
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