General Description
The MAX803/MAX809/MAX810 are microprocessor (µP)
supervisory circuits used to monitor the power supplies
in µP and digital systems. They provide excellent circuit
reliability and low cost by eliminating external compo-
nents and adjustments when used with +5V, +3.3V,
+3.0V, or +2.5V powered circuits.
These circuits perform a single function: they assert a
reset signal whenever the VCC supply voltage declines
below a preset threshold, keeping it asserted for at
least 140ms after VCC has risen above the reset thresh-
old. Reset thresholds suitable for operation with a vari-
ety of supply voltages are available.
The MAX803 has an open-drain output stage, while the
MAX809/MAX810 have push-pull outputs. The
MAX803’s open-drain RESET output requires a pull-up
resistor that can be connected to a voltage higher than
VCC. The MAX803/MAX809 have an active-low RESET
output, while the MAX810 has an active-high RESET
output. The reset comparator is designed to ignore fast
transients on VCC, and the outputs are guaranteed to
be in the correct logic state for VCC down to 1V.
Low supply current makes the MAX803/MAX809/
MAX810 ideal for use in portable equipment. The
MAX803 is available in a 3-pin SC70 package, and the
MAX809/MAX810 are available in 3-pin SC70 or SOT23
packages.
Applications
Computers
Controllers
Intelligent Instruments
Critical µP and µC Power Monitoring
Portable/Battery-Powered Equipment
Automotive
____________________________Features
♦Precision Monitoring of +2.5V, +3V, +3.3V, and
+5V Power-Supply Voltages
♦Fully Specified Over Temperature
♦Available in Three Output Configurations
Open-Drain RESET Output (MAX803)
Push-Pull RESET Output (MAX809)
Push-Pull RESET Output (MAX810)
♦140ms min Power-On Reset Pulse Width
♦12µA Supply Current
♦Guaranteed Reset Valid to VCC = +1V
♦Power Supply Transient Immunity
♦No External Components
♦3-Pin SC70 and SOT23 Packages
MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
3-Pin Microprocessor Reset Circuits
________________________________________________________________ Maxim Integrated Products 1
TOP VIEW
RESET (RESET)
1
GND
VCC
MAX803
MAX809
MAX810
SC70-3/SOT23-3
2
3
( ) ARE FOR MAX810.
MAX803 AVAILABLE IN SC70-3 ONLY.
MAX803
MAX809
VCC
VCC
RPULL-UP*
RESET RESET
INPUT
GND
VCC
GND
*MAX803 ONLY
µP
Pin Configuration
Typical Operating Circuit
19-0344; Rev 6; 12/05
Note: These parts are offered in 2.5k or 10k reels, and must be
ordered in 2.5k or 10k increments. Order MAX803_EXR-T for
2.5k reels and MAX803_EXR-T10 for 10k reels. Insert the
desired suffix letter from the Selector Guide into the blank to
complete the part number. All versions of these products may
not be available at the time of announcement. Contact factory for
availability.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
3 SC70-3-40°C to +125°CMAX803_EXR-T10
3 SC70-3
PIN-PACKAGETEMP. RANGE
-40°C to +125°C
MAX803_EXR-T
PART
3 SC70-3-40°C to +125°CMAX809_EXR-T10
3 SC70-3-40°C to +125°C
MAX809_EXR-T
3 SOT23-3-40°C to +105°CMAX809_EUR-T10
3 SOT23-3-40°C to +105°CMAX809_EUR-T
3 SC70-3-40°C to +125°CMAX810_EXR-T10
3 SC70-3-40°C to +125°C
MAX810_EXR-T
3 SOT23-3-40°C to +105°CMAX810_EUR-T10
3 SOT23-3-40°C to +105°CMAX810_EUR-T
Ordering Information
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.
MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
3-Pin Microprocessor Reset Circuits
2_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC = full range, TA= -40°C to +105°C (SOT23) or TA= -40°C to +125°C (SC70), unless otherwise noted. Typical values are at TA=
+25°C, VCC = 5V for L/M/J versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, and VCC = 2.5V for Z version.) (Note 1)
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.
Terminal Voltage (with respect to GND)
VCC ....................................................................-0.3V to +6.0V
RESET, RESET (push-pull) .....................-0.3V to (VCC + 0.3V)
RESET (open drain)...........................................-0.3V to +6.0V
Input Current, VCC ..............................................................20mA
Output Current, RESET, RESET ..........................................20mA
Rate of Rise, VCC ............................................................100V/µs
Continuous Power Dissipation (TA= +70°C)
3-Pin SC70 (derate 2.17mW/°C above +70°C)............174mW
3-Pin SOT23 (derate 4mW/°C above +70°C)...............320mW
Operating Temperature Range
3-Pin SC70.....................................................-40°C to +125°C
3-Pin SOT23...................................................-40°C to +105°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX
UNITS
TA = 0°C to +70°C 1.0 5.5
TA = -40°C to +105°C (MAX8_ _ _EUR) 1.2 5.5
VCC Range
TA = -40°C to +125°C (MAX8_ _ _EXR) 1.2 5.5
V
VCC < 5.5V, MAX8_ _L/M 24 60
TA = -40°C
to +85°C VCC < 3.6V, MAX8_ _R/S/T/Z 17 50
VCC < 5.5V, MAX8_ _L/M 100
Supply Current (SOT23) ICC TA = +85°C
to +105°C VCC < 3.6V, MAX8_ _R/S/T/Z 100
VCC < 5.5V, MAX8_ _L/M 24 35
TA = -40°C
to +85°CVCC < 3.6V, MAX8_ _R/S/T/Z 17 30
VCC < 5.5V, MAX8_ _L/M 60
Supply Current (SC70) ICC TA = +85°C
to +125°C VCC < 3.6V, MAX8_ _R/S/T/Z 60
µA
TA = +25°C
4.56 4.63 4.70
TA = -40°C to +85°C
4.50 4.75
MAX8_ _L
TA = -40°C to +125°C
4.40 4.86
TA = +25°C
4.31 4.38 4.45
TA = -40°C to +85°C
4.25 4.50
MAX8_ _M
TA = -40°C to +125°C
4.16 4.56
TA = +25°C
3.93 4.00 4.06
TA = -40°C to +85°C
3.89 4.10
MAX809J
(SOT only)
TA = -40°C to +125°C
3.80 4.20
TA = +25°C
3.04 3.08 3.11
TA = -40°C to +85°C
3.00 3.15
MAX8_ _T
TA = -40°C to +125°C
2.92 3.23
TA = +25°C
2.89 2.93 2.96
TA = -40°C to +85°C
2.85 3.00
MAX8_ _S
TA = -40°C to +125°C
2.78 3.08
TA = +25°C
2.59 2.63 2.66
TA = -40°C to +85°C
2.55 2.70
Reset Threshold
(SOT only) VTH
MAX8_ _R
TA = -40°C to +125°C
2.50 2.76
V
MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
3-Pin Microprocessor Reset Circuits
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC = full range, TA= -40°C to +105°C (SOT23) or TA= -40°C to +125°C (SC70), unless otherwise noted. Typical values are at TA=
+25°C, VCC = 5V for L/M/J versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, and VCC = 2.5V for Z version.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX
UNITS
TA = +25°C
4.56 4.63 4.70
TA = -40°C to +85°C
4.50 4.75
MAX8_ _L
TA = -40°C to +125°C
4.44 4.82
TA = +25°C
4.31 4.38 4.45
TA = -40°C to +85°C
4.25 4.50MAX8_ _M
TA = -40°C to +125°C
4.20 4.56
TA = +25°C
3.04 3.08 3.11
TA = -40°C to +85°C
3.00 3.15
MAX8_ _T
TA = -40°C to +125°C
2.95 3.21
TA = +25°C
2.89 2.93 2.96
TA = -40°C to +85°C
2.85 3.00
MAX8_ _S
TA = -40°C to +125°C
2.81 3.05
TA = +25°C
2.59 2.63 2.66
TA = -40°C to +85°C
2.55 2.70
MAX8_ _R
TA = -40°C to +125°C
2.52 2.74
TA = +25°C
2.28 2.32 2.35
TA = -40°C to +85°C
2.25 2.38
Reset Threshold
(SC70 only) VTH
MAX8_ _Z
(SC70 only)
TA = -40°C to +125°C
2.22 2.42
V
Reset Threshold Tempco 30
ppm/°C
VCC to Reset Delay (Note 2) VCC = VTH to (VTH - 100 mV) 20 µs
TA = -40°C to +85°C
140
240 560
Reset Active Timeout Period
(SOT23) TA = +85°C to +105°C
100
840 ms
TA = -40°C to +85°C
140
240 460
Reset Active Timeout Period
(SC70) TA = +85°C to +125°C
100
840 ms
VCC = VTH min, ISINK = 1.2mA,
MAX803R/S/T/Z, MAX809R/S/T/Z 0.3
VCC = VTH min, ISINK = 3.2mA,
MAX803L/M, MAX809J/L/M 0.4
RESET Output Voltage Low (push-
pull active low and open-drain
active low, MAX803 and MAX809)
VOL
VCC > 1.0V, ISINK = 50µA 0.3
V
VCC > VTH max, ISOURCE = 500µA,
MAX803R/S/T/Z, MAX809R/S/T/Z
0.8VCC
RESET Output Voltage High
(push-pull active low MAX809) VOH VCC > VTH max, ISOURCE = 800µA,
MAX803L/M, MAX809J/L/M VCC - 1.5
V
VCC = VTH max, ISINK = 1.2mA,
MAX810R/S/T/Z 0.3
RESET Output Voltage Low (push-
pull active high, MAX810) VOL VCC = VTH max, ISINK = 3.2mA,
MAX810L/M 0.4
V
MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
3-Pin Microprocessor Reset Circuits
4_______________________________________________________________________________________
225
POWER-UP RESET TIMEOUT
vs. TEMPERATURE
245
250
MAX803-TOC5
TEMPERATURE (°C)
POWER-UP RESET TIMEOUT (ms)
235
230
240
-40 85
20
-20 060
40
MAX8_ _R/S/T/Z
MAX8_ _J/L/M
0.997
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
1.001
1.002
1.003
MAX803-TOC6
TEMPERATURE (°C)
NORMALIZED THRESHOLD
0.999
0.998
1.000
-40 85
20
-20 060
40
0
POWER-DOWN RESET DELAY vs.
TEMPERATURE (MAX8_ _J/L/M)
80
100
120
140
MAX803-TOC4
TEMPERATURE (°C)
POWER-DOWN RESET DELAY (µs)
40
20
60
-40 85
20
-20 060
40
VOD = VTH - VCC
VOD = 10mV
VOD = 100mV
VOD = 200mV
VOD = 20mV
0
POWER-DOWN RESET DELAY vs.
TEMPERATURE (MAX8_ _R/S/T/Z)
80
100
MAX803-TOC3
TEMPERATURE (°C)
POWER-DOWN RESET DELAY (µs)
40
20
60
-40 85
20
-20 060
40
VOD = VTH - VCC
VOD = 20mV
VOD = 10mV
VOD = 200mV
VOD = 100mV
Typical Operating Characteristics
(VCC = full range, TA= -40°C to +105°C, unless otherwise noted. Typical values are at TA= +25°C, VCC = +5V for L/M/J versions,
VCC = +3.3V for T/S versions, VCC = +3V for R version, and VCC = +2.5V for Z version.)
ELECTRICAL CHARACTERISTICS (continued)
(VCC = full range, TA= -40°C to +105°C (SOT23) or TA= -40°C to +125°C (SC70), unless otherwise noted. Typical values are at TA=
+25°C, VCC = 5V for L/M/J versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, and VCC = 2.5V for Z version.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX
UNITS
RESET Output Voltage High
(push-pull active high, MAX810) VOH 1.8V < VCC < VTH min, ISOURCE = 150µA
0.8VCC
V
RESET Open-Drain Output
Leakage Current (MAX803)
(Note 3)
VCC > VTH, RESET deasserted 1 µA
Note 1: Production testing done at TA= +25°C; limits over temperature guaranteed by design only.
Note 2: RESET output for MAX803/MAX809; RESET output for MAX810.
Note 3: Guaranteed by design, not production tested.
MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
_______________________________________________________________________________________ 5
Detailed Description
A microprocessor’s (µP’s) reset input starts the µP in a
known state. The MAX803/MAX809/MAX810 assert
reset to prevent code-execution errors during power-
up, power-down, or brownout conditions. They assert a
reset signal whenever the VCC supply voltage declines
below a preset threshold, keeping it asserted for at
least 140ms after VCC has risen above the reset thresh-
old. The MAX803 uses an open-drain output, and the
MAX809/MAX810 have a push-pull output stage.
Connect a pull-up resistor on the MAX803’s RESET out-
put to any supply between 0 and 6V.
Applications Information
Negative-Going VCC Transients
In addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, the MAX803/
MAX809/MAX810 are relatively immune to short-duration
negative-going VCC transients (glitches).
Figure 1 shows typical transient duration vs. reset com-
parator overdrive, for which the MAX803/MAX809/
MAX810 do not generate a reset pulse. The graph was
generated using a negative-going pulse applied to VCC,
starting 0.5V above the actual reset threshold and end-
ing below it by the magnitude indicated (reset compara-
tor overdrive). The graph indicates the maximum pulse
width a negative-going VCC transient can have without
causing a reset pulse. As the magnitude of the transient
increases (goes farther below the reset threshold), the
maximum allowable pulse width decreases. Typically, for
the MAX8__L and MAX8__M, a VCC transient that goes
100mV below the reset threshold and lasts 20µs or less
will not cause a reset pulse. A 0.1µF bypass capacitor
mounted as close as possible to the VCC pin provides
additional transient immunity.
Ensuring a Valid Reset Output
Down to VCC = 0
When VCC falls below 1V, the MAX809 RESET output
no longer sinks current—it becomes an open circuit.
3-Pin Microprocessor Reset Circuits
2
RESET
(MAX803/
MAX809)
RESET Output remains low while VCC
is below the reset threshold, and for at
least 140ms after VCC rises above the
reset threshold.
1GND Ground
PIN NAME FUNCTION
RESET
(MAX810)
RESET Output remains high while VCC
is below the reset threshold, and for at
least 140ms after VCC rises above the
reset threshold.
3 VCC Supply Voltage (+5V, +3.3V, +3.0V, or
+2.5V)
Selector Guide
TOP MARK
PART/SUFFIX
RESET THRESHOLD (V)
OUTPUT TYPE SOT SC70
MAX803L 4.63 OPEN-DRAIN RESET AAZ
MAX803M 4.38 OPEN-DRAIN RESET ABA
MAX803T 3.08 OPEN-DRAIN RESET ABB
MAX803S 2.93 OPEN-DRAIN RESET ABC
MAX803R 2.63 OPEN-DRAIN RESET ABD
MAX803Z 2.32 OPEN-DRAIN RESET ABE
MAX809L 4.63 PUSH-PULL RESET AAAA AAN
MAX809M 4.38 PUSH-PULL RESET ABAA AAO
MAX809J 4.00 PUSH-PULL RESET CWAA
MAX809T 3.08 PUSH-PULL RESET ACAA AAP
MAX809S 2.93 PUSH-PULL RESET ADAA AAQ
MAX809R 2.63 PUSH-PULL RESET AFAA AAR
MAX809Z 2.32 PUSH-PULL RESET AAS
MAX810L 4.63 PUSH-PULL RESET AGAA AAT
MAX810M 4.38 PUSH-PULL RESET AHAA AAU
MAX810T 3.08 PUSH-PULL RESET AJAA AAV
MAX810S 2.93 PUSH-PULL RESET AKAA AAX
MAX810R 2.63 PUSH-PULL RESET ALAA AAW
MAX810Z 2.32 PUSH-PULL RESET AAY
Pin Description
MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
Therefore, high-impedance CMOS logic inputs con-
nected to RESET can drift to undetermined voltages.
This presents no problem in most applications since
most µP and other circuitry is inoperative with VCC
below 1V. However, in applications where RESET must
be valid down to 0V, adding a pull-down resistor to
RESET causes any stray leakage currents to flow to
ground, holding RESET low (Figure 2). R1’s value is not
critical; 100kΩis large enough not to load RESET and
small enough to pull RESET to ground.
A 100kΩpull-up resistor to VCC is also recommended
for the MAX810 if RESET is required to remain valid for
VCC < 1V.
Interfacing to µPs with
Bidirectional Reset Pins
Since the RESET output on the MAX803 is open drain,
this device interfaces easily with µPs that have bidirec-
tional reset pins, such as the Motorola 68HC11.
Connecting the µP supervisor’s RESET output directly
to the microcontroller’s (µC’s) RESET pin with a single
pull-up resistor allows either device to assert reset
(Figure 3).
MAX803 Open-Drain
RESET
Output
Allows Use with Multiple Supplies
Generally, the pull-up connected to the MAX803 will
connect to the supply voltage that is being monitored at
the IC’s VCC pin. However, some systems may use the
open-drain output to level-shift from the monitored sup-
ply to reset circuitry powered by some other supply
(Figure 4). Note that as the MAX803’s VCC decreases
3-Pin Microprocessor Reset Circuits
6_______________________________________________________________________________________
RESET
GND
RESET
INPUT
RPULLUP
MAX803
5V SYSTEM
GND
VCC
+3.3V +5.0V
VCC
Figure 4. MAX803 Open-Drain
RESET
Output Allows Use with
Multiple Supplies
RESET
GND
RESET
INPUT
MAX803 MOTOROLA
68HCXX
µP
GND
VCC
VCC
VCC
Figure 3. Interfacing to µPs with Bidirectional Reset I/O
400
320
0
1100 1000
160
80
240
RESET COMPARATOR OVERDRIVE, VTH - VCC (mV)
MAXIMUM TRANSIENT DURATION (µs)
10
TA = +25°C
MAX8_ _J/L/M
MAX8_ _R/S/T/Z
Figure 1. Maximum Transient Duration Without Causing a
Reset Pulse vs. Reset Comparator Overdrive
R1
100k
VCC
GND
MAX809
RESET
Figure 2.
RESET
Valid to VCC = Ground Circuit
below 1V, so does the IC’s ability to sink current at
RESET. Also, with any pull-up, RESET will be pulled
high as VCC decays toward 0. The voltage where this
occurs depends on the pull-up resistor value and the
voltage to which it is connected.
Benefits of Highly Accurate
Reset Threshold
Most µP supervisor ICs have reset threshold voltages
between 5% and 10% below the value of nominal sup-
ply voltages. This ensures a reset will not occur within
5% of the nominal supply, but will occur when the sup-
ply is 10% below nominal.
When using ICs rated at only the nominal supply ±5%,
this leaves a zone of uncertainty where the supply is
between 5% and 10% low, and where the reset may or
may not be asserted.
The MAX8__L/T/Z use highly accurate circuitry to
ensure that reset is asserted close to the 5% limit, and
long before the supply has declined to 10% below
nominal.
MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
3-Pin Microprocessor Reset Circuits
_______________________________________________________________________________________ 7
TRANSISTOR COUNT: 275 (SOT23)
380 (SC70)
___________________Chip Information
SC70, 3L.EPS
PACKAGE OUTLINE, 3L SC70
21-0075
1
1
C
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
3-Pin Microprocessor Reset Circuits
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
©2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.
SOTPO3L.EPS
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)