General Description
The MAX809/MAX810 are microprocessor (µP) supervi-
sory circuits used to monitor the power supplies in µP
and digital systems. They provide excellent circuit relia-
bility and low cost by eliminating external components
and adjustments when used with 5V-powered or 3V-
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 threshold.
The only difference between the two devices is that the
MAX809 has an active-low RESET output (which is guar-
anteed to be in the correct state for VCC down to 1V),
while the MAX810 has an active-high RESET output. The
reset comparator is designed to ignore fast transients on
VCC. Reset thresholds suitable for operation with a vari-
ety of supply voltages are available.
Low supply current makes the MAX809/MAX810 ideal
for use in portable equipment. The MAX809/MAX810
come in a 3-pin SOT23 package.
________________________Applications
Computers
Controllers
Intelligent Instruments
Critical µP and µC Power Monitoring
Portable/Battery-Powered Equipment
Automotive
____________________________Features
♦Precision Monitoring of 3V, 3.3V, and 5V
Power-Supply Voltages
♦Fully Specified Over Temperature
♦140ms Min Power-On Reset Pulse Width
RESET Output (MAX809)
RESET Output (MAX810)
♦17µA Supply Current
♦Guaranteed RESET Valid to VCC = 1V (MAX809)
♦Power Supply Transient Immunity
♦No External Components
♦3-Pin SOT23 Package
Ordering Information
MAX809J/L/M/R/S/T, MAX810L/M/R/S/T
3-Pin Microprocessor Reset Circuits
________________________________________________________________
Maxim Integrated Products
1
TOP VIEW
RESET (RESET)
1
GND
VCC
MAX809
MAX810
SOT23-3
2
3
( ) ARE FOR MAX810.
MAX809
VCC
VCC
RESET RESET
INPUT
GND
VCC
GND
µP
__________________Pin Configuration
__________Typical Operating Circuit
PART†
MAX809_EUR-T -40°C to +105°C
TEMP. RANGE PIN-PACKAGE
3 SOT23-3
MAX809_EUR-T10 -40°C to +105°C 3 SOT23-3
SUFFIX
L
M
J*
S
R
19-0344; Rev 3; 3/98
T
Ordering Information continued at end of data sheet.
Note:
These parts are offered in 2.5k or 10k reels, and must be
ordered in 2.5k or 10k increments. Order MAX809_EUR-T for
2.5k reels and MAX809_EUR-T10 for 10k reels.
†
Insert the desired suffix letter (from the table below) into the
blank to complete the part number:
*
J version is available for MAX809 only.
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
RESET
THRESHOLD (V)
4.63
4.38
4.00
2.93
2.63
3.08
AAAA
ABAA
CWAA
ADAA
AFAA
ACAA
SOT TOP MARK
AGAA
AHAA
—
AKAA
ALAA
AJAA
MAX809 MAX810
MAX809J/L/M/R/S/T, MAX810L/M/R/S/T
3-Pin Microprocessor Reset Circuits
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL 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, and VCC = 3V for R 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..........................................-0.3V to (VCC + 0.3V)
Input Current, VCC ..............................................................20mA
Output Current, RESET, RESET ..........................................20mA
Rate of Rise, VCC.......................................................................100V/µs
Continuous Power Dissipation (TA= +70°C)
SOT23 (derate above +70°C by 4mW/°C)...................320mW
Operating Temperature Range .........................-40°C to +105°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
VCC = VTH to (VTH - 100mV)
CONDITIONS
µs20VCC to Reset Delay (Note 2)
3.00 3.15
4.25 4.50
4.56 4.63 4.70
4.50 4.75
4.40 4.86
4.31 4.38 4.45
UNITSMIN TYP MAXSYMBOLPARAMETER
MAX8_ _L
MAX8_ _M
VTH
Reset Threshold (Note 2)
MAX809J
V
3.04 3.08 3.11
4.16 4.56
3.93 4.00 4.06
3.89 4.10
3.80 4.20
TA= +25°C
TA= -40°C to +85°C
TA= +85°C to +105°C
TA= +25°C
TA= -40°C to +85°C
TA= +85°C to +105°C
TA= +25°C
TA= -40°C to +85°C
TA= +85°C to +105°C
TA= +25°C
VCC = VTH min, ISINK = 1.2mA, MAX809R/S/T 0.3
VCC = VTH min, ISINK = 3.2mA, MAX809L/M 0.4
VCC > 1.0V, ISINK = 50µA V
0.3
VOL
RESET Output Voltage Low
(MAX809)
TA= -40°C to +105°C 1.2 5.5
TA= 0°C to +70°C V
1.0 5.5
VCC Range
TA= -40°C to
+85°C µA
17 50
ICC
Supply Current
24 60
ppm/°C30Reset Threshold Tempco
2.92 3.23
TA= -40°C to +85°C
TA= +85°C to +105°C
TA= +85°C to
+105°C 100
100VCC < 5.5V, MAX8_ _ L/M
TA= -40°C to +85°C
TA= +85°C to +105°C 100 840
Reset Active Timeout Period ms
140 240 560
MAX8_ _S TA= +25°C
TA= -40°C to +85°C
TA= +85°C to +105°C
TA= +25°C
TA= -40°C to +85°C
TA= +85°C to +105°C
MAX8_ _R 2.50 2.76
2.55 2.70
2.89 2.93 2.96
2.85 3.00
2.78 3.08
2.59 2.63 2.66
MAX8_ _T
VCC < 5.5V, MAX8_ _ L/M
VCC < 3.6V, MAX8_ _ R/S/T
VCC < 3.6V, MAX8_ _ R/S/T
MAX809J/L/M/R/S/T, MAX810L/M/R/S/T
3-Pin Microprocessor Reset Circuits
_______________________________________________________________________________________
3
35
0-40 85
SUPPLY CURRENT vs. TEMPERATURE
(NO LOAD, MAX8_ _R/S/T)
20
25
30
MAX809/10-TOC1
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
20
10
5
-20 060
15
40
VCC = 5V
VCC = 3V
VCC = 1V
0
SUPPLY CURRENT vs. TEMPERATURE
(NO LOAD, MAX8_ _L/M)
20
25
30
MAX809/10-TOC2
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
10
5
15
-40 85
20
-20 060
40
VCC = 5V
VCC = 3V
VCC = 1V
0
POWER-DOWN RESET DELAY vs.
TEMPERATURE (MAX8_ _R/S/T)
80
100
MAX809/10-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
0
POWER-DOWN RESET DELAY vs.
TEMPERATURE (MAX8_ _L/M)
80
100
120
140
MAX809/10-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
225
POWER-UP RESET TIMEOUT
vs. TEMPERATURE
245
250
MAX809/10-TOC5
TEMPERATURE (°C)
POWER-UP RESET TIMEOUT (ms)
235
230
240
-40 85
20
-20 060
40
MAX8_ _R/S/T
MAX8_ _L/M
0.997
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
1.001
1.002
1.003
MAX809/10-TOC6
TEMPERATURE (°C)
NORMALIZED THRESHOLD
0.999
0.998
1.000
-40 85
20
-20 060
40
__________________________________________Typical Operating Characteristics
ELECTRICAL CHARACTERISTICS (continued)
(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, and VCC = 3V for R version.) (Note 1)
Note 1: Production testing done at TA= +25°C, over temperature limits guaranteed by design only.
Note 2: RESET Output for MAX809, RESET Output for MAX810.
VCC = VTH max, ISINK = 1.2mA, MAX810R/S/T
VCC > VTH max, ISOURCE = 500µA,
MAX809R/S/T
CONDITIONS
V
VCC - 1.5
VOH
RESET Output Voltage High
(MAX809)
V
V0.8VCC
VOH
RESET Output Voltage High
(MAX810)
0.4
VCC > VTH max, ISOURCE = 800µA,
MAX809L/M
VOL
RESET Output Voltage Low
(MAX810) VCC = VTH max, ISINK = 3.2mA, MAX810L/M 0.3
0.8VCC
1.8V < VCC < VTH min, ISOURCE = 150µA
UNITSMIN TYP MAXSYMBOLPARAMETER
MAX809J/L/M/R/S/T, MAX810L/M/R/S/T
__________Applications Information
Negative-Going V
CC
Transients
In addition to issuing a reset to the microprocessor (µP)
during power-up, power-down, and brownout condi-
tions, the 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 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 ending
below it by the magnitude indicated (reset comparator
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 tran-
sient increases (goes farther below the reset threshold),
the maximum allowable pulse width decreases.
Typically, for the MAX809L and MAX810M, a VCC tran-
sient 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 V
CC
= 0V
When VCC falls below 1V, the MAX809 RESET output
no longer sinks current—it becomes an open circuit.
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.
3-Pin Microprocessor Reset Circuits
4 _______________________________________________________________________________________
2
RESET
(MAX809)
RESET Output remains low while VCC
is below the reset threshold, and for
240ms after VCC rises above the reset
threshold.
1 GND Ground
PIN NAME FUNCTION
RESET
(MAX810)
RESET Output remains high while VCC
is below the reset threshold, and for
240ms after VCC rises above the reset
threshold.
_____________________Pin Description
400
320
01 100 1000
160
80
240
RESET COMPARATOR OVERDRIVE , VTH - VCC (mV)
MAXIMUM TRANSIENT DURATION (µs)
10
TA = +25°C
MAX8_ _L/M
MAX8_ _R/S/T
Figure 1. Maximum Transient Duration without Causing a
Reset Pulse vs. Reset Comparator Overdrive
3 VCC Supply Voltage (+5V, +3.3V, or +3.0V)
Interfacing to µPs with
Bidirectional Reset Pins
µPs with bidirectional reset pins (such as the Motorola
68HC11 series) can connect to the MAX809 reset out-
put. If, for example, the MAX809 RESET output is
asserted high and the µP wants to pull it low, indetermi-
nate logic levels may result. To correct this, connect a
4.7kΩresistor between the MAX809 RESET output and
the µP reset I/O (Figure 3). Buffer the MAX809 RESET
output to other system components.
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 MAX809L/T and MAX810L/T 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.
MAX809J/L/M/R/S/T, MAX810L/M/R/S/T
3-Pin Microprocessor Reset Circuits
_______________________________________________________________________________________ 5
R1
100k
VCC
GND
MAX809
RESET
Figure 2. RESET Valid to VCC = Ground Circuit
4.7k
VCC
GND
RESET
MAX809
RESET
VCC
GND
µP
BUFFER BUFFERED RESET
TO OTHER SYSTEM
COMPONENTS
Figure 3. Interfacing to µPs with Bidirectional Reset I/O
TRANSISTOR COUNT: 275
___________________Chip Information
PART†
MAX810_EUR-T -40°C to +105°C
TEMP. RANGE PIN-PACKAGE
3 SOT23-3
MAX810_EUR-T10 -40°C to +105°C 3 SOT23-3
Ordering Information (continued)
Note:
These parts are offered in 2.5k or 10k reels, and must be
ordered in 2.5k or 10k increments. Order MAX809_EUR-T for
2.5k reels and MAX809_EUR-T10 for 10k reels.
†
Insert the desired suffix letter (from the table below) into the
blank to complete the part number:
SUFFIX
L
M
J*
RESET
THRESHOLD (V)
4.63
4.38
4.00
2.93
2.63
3.08
AAAA
ABAA
S
R
CWAA
ADAA
AFAA
ACAA
SOT TOP MARK
AGAA
T
AHAA
—
AKAA
ALAA
AJAA
MAX809 MAX810
*
J version is available for MAX809 only.
MAX809J/L/M/R/S/T, MAX810L/M/R/S/T
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.
6
_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
________________________________________________________Package Information
SOTPO3L.EPS
