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19-0344; Rev 4; 12/99
3-Pin Microprocessor Reset Circuits
General Description
The MAX803/MAX809/MAX810 are microprocessor (P) supervisory circuits used to monitor the power supplies in P and digital systems. They provide excellent circuit reliability and low cost by eliminating external components 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 threshold. Reset thresholds suitable for operation with a variety 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.
____________________________Features
o Precision Monitoring of +2.5V, +3V, +3.3V, and +5V Power-Supply Voltages o Fully Specified Over Temperature o Available in Three Output Configurations Open-Drain RESET Output (MAX803) Push-Pull RESET Output (MAX809) Push-Pull RESET Output (MAX810) o 140ms min Power-On Reset Pulse Width o 12A Supply Current o Guaranteed Reset Valid to VCC = +1V o Power Supply Transient Immunity o No External Components o 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
Ordering Information
PART MAX803_EXR-T MAX803_EXR-T10 MAX809_EXR-T MAX809_EXR-T10 MAX809_EUR-T MAX809_EUR-T10 MAX810_EXR-T MAX810_EXR-T10 MAX810_EUR-T MAX810_EUR-T10 TEMP. RANGE -40C to +105C -40C to +105C -40C to +105C -40C to +105C -40C to +105C -40C to +105C -40C to +105C -40C to +105C -40C to +105C -40C to +105C PIN-PACKAGE 3 SC70-3 3 SC70-3 3 SC70-3 3 SC70-3 3 SOT23-3 3 SOT23-3 3 SC70-3 3 SC70-3 3 SOT23-3 3 SOT23-3
Applications
Computers Controllers Intelligent Instruments Critical P and C Power Monitoring Portable/Battery-Powered Equipment Automotive
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.
Typical Operating Circuit
TOP VIEW
VCC GND 1 VCC RPULL-UP* VCC
Pin Configuration
MAX803 MAX809
RESET RESET INPUT
P
MAX803 MAX809 MAX810
3
VCC
RESET (RESET) 2 GND GND ( ) ARE FOR MAX810. MAX803 AVAILABLE IN SC70-3 ONLY.
SC70-3/SOT23-3
*MAX803 ONLY
________________________________________________________________ Maxim Integrated Products
1
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3-Pin Microprocessor Reset Circuits MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
ABSOLUTE MAXIMUM RATINGS
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/s Continuous Power Dissipation (TA = +70C) 3-Pin SC70 (derate 2.17mW/C above +70C) ............174mW 3-Pin SOT23 (derate 4mW/C above +70C)...............320mW Operating Temperature Range .........................-40C to +105C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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
(VCC = full range, TA = -40C to +105C, unless otherwise noted. Typical values are at TA = +25C, 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 VCC Range SYMBOL CONDITIONS TA = 0C to +70C TA = -40C to +105C TA = -40C to +85C Supply Current (SOT23) ICC TA = +85C to +105C TA = -40C to +85C Supply Current (SC70) ICC TA = +85C to +105C MAX8_ _L VCC < 5.5V, MAX8_ _J/L/M VCC < 3.6V, MAX8_ _R/S/T VCC < 5.5V, MAX8_ _L/M VCC < 3.6V, MAX8_ _R/S/T VCC < 5.5V, MAX8_ _L/M VCC < 3.6V, MAX8_ _R/S/T/Z VCC < 5.5V, MAX8_ _L/M VCC < 3.6V, MAX8_ _R/S/T/Z TA = +25C TA = -40C to +85C TA = +85C to +105C TA = +25C MAX8_ _M TA = -40C to +85C TA = +85C to +105C MAX809J (SOT only) TA = +25C TA = -40C to +85C TA = +85C to +105C TA = +25C Reset Threshold VTH MAX8_ _T TA = -40C to +85C TA = +85C to +105C TA = +25C MAX8_ _S TA = -40C to +85C TA = +85C to +105C TA = +25C MAX8_ _R TA = -40C to +85C TA = +85C to +105C MAX8_ _Z (SC70 only) TA = +25C TA = -40C to +85C TA = +85C to +105C 2 4.56 4.50 4.40 4.31 4.25 4.16 3.93 3.89 3.80 3.04 3.00 2.92 2.89 2.85 2.78 2.59 2.55 2.50 2.28 2.25 2.21 2.32 2.63 2.93 3.08 4.00 4.38 4.63 16 12 MIN 1.0 1.2 24 17 TYP MAX 5.5 5.5 60 50 100 100 35 30 75 75 4.70 4.75 4.86 4.45 4.50 4.56 4.06 4.10 4.20 3.11 3.15 3.23 2.96 3.00 3.08 2.66 2.70 2.76 2.35 2.38 2.45 V A UNITS V
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3-Pin Microprocessor Reset Circuits
ELECTRICAL CHARACTERISTICS (continued)
(VCC = full range, TA = -40C to +105C, unless otherwise noted. Typical values are at TA = +25C, 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 Reset Threshold Tempco VCC to Reset Delay (Note 2) Reset Active Timeout Period (SOT23) Reset Active Timeout Period (SC70) RESET Output Voltage Low (push-pull active low and opendrain active-low, MAX803 and MAX809) VCC = VTH to (VTH - 100mV) TA = -40C to +85C TA = +85C to +105C TA = -40C to +85C TA = +85C to +105C VCC = VTH min, ISINK = 1.2mA, MAX803R/S/T/Z, MAX809R/S/T/Z VOL VCC = VTH min, ISINK = 3.2mA, MAX803L/M, MAX809J/L/M VCC > 1.0V, ISINK = 50A RESET Output Voltage High (push-pull active low, MAX809) VCC > VTH max, ISOURCE = 500A, MAX809R/S/T/Z VOH VCC > VTH max, ISOURCE = 800A, MAX809J/L/M VCC = VTH max, ISINK = 1.2mA, MAX810R/S/T/Z VOL VCC = VTH max, ISINK = 3.2mA, MAX810L/M 1.8V < VCC < VTH min, ISOURCE = 150A VCC > VTH, RESET deasserted 0.8VCC 1 0.8VCC V VCC - 1.5 0.3 V 0.4 V A 140 100 140 100 240 SYMBOL CONDITIONS MIN TYP 30 20 240 560 840 460 840 0.3 0.4 0.3 V MAX UNITS ppm/C s ms ms
MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
RESET Output Voltage Low (push-pull active high, MAX810)
RESET Output Voltage High (push-pull active high, MAX810) RESET Open-Drain Output Leakage Current (MAX803)
VOH
Note 1: Production testing done at TA = +25C; limits over temperature guaranteed by design only. Note 2: RESET output for MAX803/MAX809; RESET output for MAX810.
Typical Operating Characteristics
(VCC = full range, TA = -40C to +105C, unless otherwise noted. Typical values are at TA = +25C, 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.)
SUPPLY CURRENT vs. TEMPERATURE (SC70 PACKAGE, NO LOAD)
MAX803 toc01
POWER-DOWN RESET DELAY vs. TEMPERATURE (MAX8_ _R/S/T/Z)
VOD = VTH - VCC VOD = 10mV
MAX803-TOC3
15
100 POWER-DOWN RESET DELAY (s)
MAX8_ _L/M, VCC = 5V SUPPLY CURRENT (A) 10 MAX8_ _R/S/T, VCC = 3.3V MAX8_ _Z, VCC = 2.5V 5
80
60 VOD = 20mV 40
20 0
VOD = 100mV VOD = 200mV -40 -20 20 0 40 TEMPERATURE (C) 60 85
MAX8_ _L/M/R/S/T/Z, VCC = 1V 0 -40 -20 0 20 40 60 85 TEMPERATURE (C)
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3
3-Pin Microprocessor Reset Circuits MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
Typical Operating Characteristics (continued)
(VCC = full range, TA = -40C to +105C, unless otherwise noted. Typical values are at TA = +25C, 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.)
POWER-DOWN RESET DELAY vs. TEMPERATURE (MAX8_ _J/L/M)
MAX803-TOC4
POWER-UP RESET TIMEOUT vs. TEMPERATURE
MAX803-TOC5
NORMALIZED RESET THRESHOLD vs. TEMPERATURE
MAX803-TOC6
140 POWER-DOWN RESET DELAY (s) 120 100 80 60 40 20 0 -40 -20
VOD = VTH - VCC VOD = 10mV
250 POWER-UP RESET TIMEOUT (ms)
1.003 1.002
MAX8_ _J/L/M 240 MAX8_ _R/S/T/Z 235
NORMALIZED THRESHOLD 85
245
VOD = 20mV
1.001 1.000 0.999 0.998 0.997
VOD = 100mV VOD = 200mV 20 0 40 TEMPERATURE (C) 60 85
230 225 -40 -20 0 20 40 60 TEMPERATURE (C)
-40
-20
0
20
40
60
85
TEMPERATURE (C)
Selector Guide
PART/SUFFIX MAX803L MAX803M MAX803T MAX803S MAX803R MAX803Z MAX809L MAX809M MAX809J MAX809T MAX809S MAX809R MAX809Z MAX810L MAX810M MAX810T MAX810S MAX810R MAX810Z 4 RESET THRESHOLD (V) 4.63 4.38 3.08 2.93 2.63 2.32 4.63 4.38 4.00 3.08 2.93 2.63 2.32 4.63 4.38 3.08 2.93 2.63 2.32 OUTPUT TYPE Open-Drain RESET Open-Drain RESET Open-Drain RESET Open-Drain RESET Open-Drain RESET Open-Drain RESET Push-Pull RESET Push-Pull RESET Push-Pull RESET Push-Pull RESET Push-Pull RESET Push-Pull RESET Push-Pull RESET Push-Pull RESET Push-Pull RESET Push-Pull RESET Push-Pull RESET Push-Pull RESET Push-Pull RESET TOP MARK SOT -- -- -- -- -- -- AAAA ABAA CWAA ACAA ADAA AFAA -- AGAA AHAA AJAA AKAA ALAA -- SC70 AAZ ABA ABB ABC ABD ABE AAN AAO -- AAP AAQ AAR AAS AAT AAU AAV AAX AAW AAY
_______________________________________________________________________________________
3-Pin Microprocessor Reset Circuits
_____________________Pin Description
PIN 1 NAME GND RESET (MAX803/ MAX809) 2 RESET (MAX810) Ground RESET Output remains low while VCC is below the reset threshold, and for at least 140ms after VCC rises above the reset threshold. RESET Output remains high while VCC is below the reset threshold, and for at least 140ms after VCC rises above the reset threshold. Supply Voltage (+5V, +3.3V, +3.0V, or +2.5V) FUNCTION
VCC
MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
MAX809
RESET R1 100k
GND
3
VCC
Figure 2. RESET Valid to VCC = Ground Circuit
Applications Information
400 MAXIMUM TRANSIENT DURATION (s) TA = +25C 320
Negative-Going VCC Transients
In addition to issuing a reset to the P 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 comparator 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 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 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 20s or less will not cause a reset pulse. A 0.1F bypass capacitor mounted as close as possible to the VCC pin provides additional transient immunity.
240
160 MAX8_ _J/L/M 80 MAX8_ _R/S/T/Z 0 1 10 100 1000 RESET COMPARATOR OVERDRIVE, VTH - VCC (mV)
Figure 1. Maximum Transient Duration Without Causing a Reset Pulse vs. Reset Comparator Overdrive
Detailed Description
A microprocessor's (P's) reset input starts the P in a known state. The MAX803/MAX809/MAX810 assert reset to prevent code-execution errors during powerup, 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 threshold. 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 output to any supply between 0 and 6V.
When VCC falls below 1V, the MAX809 RESET output no longer sinks current--it becomes an open circuit. Therefore, high-impedance CMOS logic inputs connected to RESET can drift to undetermined voltages. This presents no problem in most applications since most P and other circuitry is inoperative with V CC 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
5
Ensuring a Valid Reset Output Down to VCC = 0
_______________________________________________________________________________________
3-Pin Microprocessor Reset Circuits MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
+3.3V +5.0V
VCC
VCC
VCC
VCC RPULLUP
VCC
MAX803
RESET
P
MOTOROLA RESET 68HCXX INPUT
5V SYSTEM
RESET INPUT
MAX803
RESET
GND
GND
GND
GND
Figure 3. Interfacing to Ps with Bidirectional Reset I/O
Figure 4. MAX803 Open-Drain RESET Output Allows Use with Multiple Supplies
ground, holding RESET low (Figure 2). R1's value is not critical; 100k is large enough not to load RESET and small enough to pull RESET to ground. A 100k pull-up resistor to VCC is also recommended for the MAX810 if RESET is required to remain valid for VCC < 1V.
Benefits of Highly Accurate Reset Threshold
Most P supervisor ICs have reset threshold voltages between 5% and 10% below the value of nominal supply voltages. This ensures a reset will not occur within 5% of the nominal supply, but will occur when the supply 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.
Interfacing to Ps with Bidirectional Reset Pins
Since the RESET output on the MAX803 is open drain, this device interfaces easily with Ps that have bidirectional reset pins, such as the Motorola 68HC11. Connecting the P supervisor's RESET output directly to the microcontroller's (C'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 supply to reset circuitry powered by some other supply (Figure 4). Note that as the MAX803's VCC decreases 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.
___________________Chip Information
TRANSISTOR COUNT: 275 (SOT23) 380 (SC70)
6
_______________________________________________________________________________________
3-Pin Microprocessor Reset Circuits
Package Information
SC70, 3L.EPS
MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
_______________________________________________________________________________________
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3-Pin Microprocessor Reset Circuits MAX803L/M/R/S/T/Z, MAX809J/L/M/R/S/T/Z, MAX810L/M/R/S/T/Z
Package Information (continued)
SOTPO3L.EPS
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 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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