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19-0411; Rev 3; 3/99
4-Pin P Voltage Monitors with Manual Reset Input MAX811/MAX812
________________General Description
The MAX811/MAX812 are low-power microprocessor (P) supervisory circuits used to monitor power supplies in P and digital systems. They provide excellent circuit reliability and low cost by eliminating external components and adjustments when used with 5Vpowered or 3V-powered circuits. The MAX811/MAX812 also provide a debounced manual reset input. These devices perform a single function: They assert a reset signal whenever the V CC supply voltage falls 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 MAX811 has an active-low RESET output (which is guaranteed to be in the correct state for VCC down to 1V), while the MAX812 has an active-high RESET output. The reset comparator is designed to ignore fast transients on VCC. Reset thresholds are available for operation with a variety of supply voltages. Low supply current makes the MAX811/MAX812 ideal for use in portable equipment. The devices come in a 4-pin SOT143 package.
____________________________Features
o Precision Monitoring of 3V, 3.3V, and 5V Power-Supply Voltages o 6A Supply Current o 140ms Min Power-On Reset Pulse Width; RESET Output (MAX811), RESET Output (MAX812) o Guaranteed Over Temperature o Guaranteed RESET Valid to VCC = 1V (MAX811) o Power-Supply Transient Immunity o No External Components o 4-Pin SOT143 Package
_______________Ordering Information
PART* MAX811_EUS-T TEMP. RANGE -40C to +85C PIN-PACKAGE 4 SOT143
________________________Applications
Computers Controllers Intelligent Instruments Critical P and C Power Monitoring Portable/Battery-Powered Equipment
MAX812_EUS-T -40C to +85C 4 SOT143 * This part offers a choice of five different reset threshold voltages. Select the letter corresponding to the desired nominal reset threshold voltage, and insert it into the blank to complete the part number. RESET THRESHOLD SUFFIX L M T S R VOLTAGE (V) 4.63 4.38 3.08 2.93 2.63
___________ Typical Operating Circuit
VCC VCC VCC
___________________Pin Configuration
TOP VIEW
GND 1 4 VCC
MAX811 MAX812
MR GND RESET (RESET)
P
RESET INPUT (RESET) RESET GND 2
MAX811 MAX812
3
MR
PUSHBUTTON SWITCH
SOT143
( ) ARE FOR MAX812 ( ) ARE FOR MAX812 NOTE: SEE LAST PAGE FOR MARKING INFORMATION.
________________________________________________________________ Maxim Integrated Products
1
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4-Pin P Voltage Monitors with Manual Reset Input MAX811/MAX812
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND) VCC ......................................................................-0.3V to 6.0V All Other Inputs.......................................-0.3V to (VCC + 0.3V) Input Current, VCC, MR .......................................................20mA Output Current, RESET or RESET .......................................20mA Continuous Power Dissipation (TA = +70C) SOT143 (derate 4mW/C above +70C) 320mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10sec) .............................+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 = 5V for L/M versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Operating Voltage Range Supply Current SYMBOL VCC ICC CONDITIONS TA = 0C to +70C TA = -40C to +85C MAX81_L/M, VCC = 5.5V, IOUT = 0 MAX81_R/S/T, VCC = 3.6V, IOUT = 0 MAX81_L MAX81_M Reset Threshold VTH MAX81_T MAX81_S MAX81_R Reset Threshold Tempco VCC to Reset Delay (Note 2) Reset Active Timeout Period MR Minimum Pulse Width MR Glitch Immunity (Note 3) MR to Reset Propagation Delay (Note 2) tMD VIH MR Input Threshold VIL VIH VIL MR Pull-Up Resistance VOH RESET Output Voltage (MAX812) ISOURCE = 150A, 1.8V < VCC < VTH(MIN) MAX812R/S/T only, ISINK = 1.2mA, VCC = VTH(MAX) MAX812L/M only, ISINK = 3.2mA, VCC = VTH(MAX) VCC > VTH(MAX), MAX81_L/M VCC > VTH(MAX), MAX81_R/S/T 2.3 0.8 0.7 x VCC 0.25 x VCC 10 0.8VCC 0.3 0.4 V 20 30 k V tRP tMR VOD = 125mV, MAX81_L/M VOD = 125mV, MAX81_R/S/T VCC = VTH(MAX) 140 10 100 0.5 TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C 4.54 4.50 4.30 4.25 3.03 3.00 2.88 2.85 2.58 2.55 30 40 20 560 2.63 2.93 3.08 4.38 MIN 1.0 1.2 6 2.7 4.63 15 10 4.72 4.75 4.46 4.50 3.14 3.15 2.98 3.00 2.68 2.70 ppm/C s ms s ns s V TYP MAX 5.5 UNITS V A
VOL
2
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4-Pin P Voltage Monitors with Manual Reset Input
ELECTRICAL CHARACTERISTICS (continued)
(VCC = 5V for L/M versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL CONDITIONS MAX811R/S/T only, ISINK = 1.2mA, VCC = VTH(MIN) VOL RESET Output Voltage (MAX811) VOH MAX811L/M only, ISINK = 3.2mA, VCC = VTH(MIN) ISINK = 50A, VCC > 1.0V MAX811R/S/T only, ISOURCE = 500A, VCC > VTH(MAX) MAX811L/M only, ISOURCE = 800A, VCC > VTH(MAX) 0.8VCC VCC - 1.5 MIN TYP MAX 0.3 0.4 0.3 V UNITS
MAX811/MAX812
Note 1: Production testing done at TA = +25C, over temperature limits guaranteed by design using six sigma design limits. Note 2: RESET output for MAX811, RESET output for MAX812. Note 3: "Glitches" of 100ns or less typically will not generate a reset pulse.
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3
4-Pin P Voltage Monitors with Manual Reset Input MAX811/MAX812
__________________________________________Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE (MAX81_R/S/T)
MAX811/12-TOC1
SUPPLY CURRENT vs. TEMPERATURE (MAX81_L/M)
MAX811/12-TOC2
POWER-DOWN RESET DELAY vs. TEMPERATURE (MAX81_R/S/T)
VOD = VTH - VCC VOD = 20mV POWER-DOWN RESET DELAY (s)
MAX811/12-TOC3
3.0 2.5 SUPPLY CURRENT (A) 2.0 1.5 1.0 0.5 0 -40 -15 10 35 60 VCC = 3.6V VCC = 3.3V
8
100
SUPPLY CURRENT (A)
6
VCC = 5.5V
80
60
4
40 VOD = 125mV 20 VOD = 200mV 0
2
VCC = 3V VCC = 1V
VCC = 1V 0 85 -40 -15 TEMPERATURE (C)
10 35 TEMPERATURE (C)
60
85
-40
-15
10
35
60
85
TEMPERATURE (C)
POWER-DOWN RESET DELAY vs. TEMPERATURE (MAX81_L/M)
MAX811/12-TOC4
POWER-UP RESET TIMEOUT vs. TEMPERATURE
POWER-UP RESET TIMEOUT (ms) MAX81_R/S/T 220
MAX811/12-TOC5
RESET THRESHOLD DEVIATION vs. TEMPERATURE
MAX811/12-TOC6
200 POWER-DOWN RESET DELAY (s)
VOD = VTH - VCC VOD = 20mV
230
1.0005 NORMALIZED THRESHOLD (V) 1.0000
150
0.9995
100
210
0.9990
50
VOD = 125mV VOD = 200mV -40 -15 10 35 60 85 TEMPERATURE (C)
200
MAX81_L/M
0.9985 0.9980
0
190 -40 -15 10 35 60 85 TEMPERATURE (C)
-40
-15
10
35
60
85
TEMPERATURE (C)
4
_______________________________________________________________________________________
4-Pin P Voltage Monitors with Manual Reset Input
______________________________________________________________ Pin Description
PIN NAME MAX811 1 2 MAX812 1 -- GND RESET Ground Active-Low Reset Output. RESET remains low while VCC is below the reset threshold or while MR is held low. RESET remains low for the Reset Active Timeout Period (tRP) after the reset conditions are terminated. Active-High Reset Output. RESET remains high while VCC is below the reset threshold or while MR is held low. RESET remains high for Reset Active Timeout Period (tRP) after the reset conditions are terminated. Manual Reset Input. A logic low on MR asserts reset. Reset remains asserted as long as MR is low and for 180ms after MR returns high. This active-low input has an internal 20k pull-up resistor. It can be driven from a TTL or CMOS-logic line, or shorted to ground with a switch. Leave open if unused. +5V, +3.3V, or +3V Supply Voltage FUNCTION
MAX811/MAX812
--
2
RESET
3
3
MR
4
4
VCC
_______________ Detailed Description
Reset Output
A microprocessor's (P's) reset input starts the P in a known state. These P supervisory circuits assert reset to prevent code execution errors during power-up, power-down, or brownout conditions. RESET is guaranteed to be a logic low for VCC > 1V. Once V CC exceeds the reset threshold, an internal timer keeps RESET low for the reset timeout period; after this interval, RESET goes high. If a brownout condition occurs (VCC dips below the reset threshold), RESET goes low. Any time VCC goes below the reset threshold, the internal timer resets to zero, and RESET goes low. The internal timer starts after VCC returns above the reset threshold, and RESET remains low for the reset timeout period. The manual reset input (MR) can also initiate a reset. See the Manual Reset Input section. The MAX812 has an active-high RESET output that is the inverse of the MAX811's RESET output.
Manual Reset Input
Many P-based products require manual reset capability, allowing the operator, a test technician, or external logic circuitry to initiate a reset. A logic low on MR asserts reset. Reset remains asserted while MR is low, and for the Reset Active Timeout Period (tRP) after MR returns high. This input has an internal 20k pull-up resistor, so it can be left open if it is not used. MR can be driven with TTL or CMOS-logic levels, or with opendrain/collector outputs. Connect a normally open momentary switch from MR to GND to create a manualreset function; external debounce circuitry is not required. If MR is driven from long cables or if the device is used in a noisy environment, connecting a 0.1F capacitor from MR to ground provides additional noise immunity.
Reset Threshold Accuracy
The MAX811/MAX812 are ideal for systems using a 5V 5% or 3V 5% power supply with ICs specified for 5V 10% or 3V 10%, respectively. They are designed to meet worst-case specifications over temperature. The reset is guaranteed to assert after the power supply falls out of regulation, but before power drops below the minimum specified operating voltage range for the system ICs. The thresholds are pre-trimmed and exhibit tight distribution, reducing the range over which an undesirable reset may occur.
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4-Pin P Voltage Monitors with Manual Reset Input MAX811/MAX812
8 MAXIMUM TRANSIENT DURATION (ms) TA = +25C 7 6 5 4 3 2 1 0 1 10 100 1000 RESET COMPARATOR OVERDRIVE , VTH - VCC (mV) GND MAX81 _R/S/T MAX81 _L/M VCC
MAX811
RESET R1
Figure 1. Maximum Transient Duration without Causing a Reset Pulse vs. Comparator Overdrive
Figure 2. RESET Valid to VCC = Ground Circuit
__________ Applications Information
Negative-Going VCC Transients In addition to issuing a reset to the P during power-up, power-down, and brownout conditions, the MAX811/ MAX812 are relatively immune to short duration negative-going VCC transients (glitches). Figure 1 shows typical transient durations vs. reset comparator overdrive, for which the MAX811/MAX812 do not generate a reset pulse. This graph was generated using a negative-going pulse applied to VCC, starting above the actual reset threshold and ending below it by the magnitude indicated (reset comparator overdrive). The graph indicates the typical maximum pulse width a negative-going VCC transient may have without causing a reset pulse to be issued. As the magnitude of the transient increases (goes farther below the reset threshold), the maximum allowable pulse width decreases. Typically, a VCC transient that goes 125mV below the reset threshold and lasts 40s or less (MAX81_L/M) or 20s or less (MAX81_T/S/R) will not cause a reset pulse to be issued. A 0.1F capacitor mounted as close as possible to VCC provides additional transient immunity.
When VCC falls below 1V, the MAX811 RESET output no longer sinks current--it becomes an open circuit. Therefore, high-impedance CMOS-logic inputs connected to the RESET output can drift to undetermined voltages. This presents no problem in most applications, since most P and other circuitry is inoperative with VCC below 1V. However, in applications where the RESET output must be valid down to 0V, adding a pulldown resistor to the RESET pin will cause any stray leakage currents to flow to 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 MAX812 if RESET is required to remain valid for VCC < 1V.
Ensuring a Valid RESET Output Down to VCC = 0V
6
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4-Pin P Voltage Monitors with Manual Reset Input
Interfacing to Ps with Bidirectional Reset Pins
Ps with bidirectional reset pins (such as the Motorola 68HC11 series) can contend with the MAX811/MAX812 reset outputs. If, for example, the MAX811 RESET output is asserted high and the P wants to pull it low, indeterminate logic levels may result. To correct such cases, connect a 4.7k resistor between the MAX811 RESET (or MAX812 RESET) output and the P reset I/O (Figure 3). Buffer the reset output to other system components.
BUFFER BUFFERED RESET TO OTHER SYSTEM COMPONENTS
MAX811/MAX812
VCC
VCC P RESET
MAX811
RESET
4.7k
___________________Chip Information
TRANSISTOR COUNT: 341
GND GND
Figure 3. Interfacing to Ps with Bidirectional Reset I/O
_______________________________________________________________________________________
7
4-Pin P Voltage Monitors with Manual Reset Input MAX811/MAX812
________________________________________________________Package Information
4.0 0.1 o1.5 0.1 2.0 0.05 1.75 0.1
8.0 0.2
4.0 0.1
3.5 0.05 o1.1 0.1
MARKING INFORMATION LOT SPECIFIC CODE XX XX
NOTE: DIMENSIONS ARE IN MM. AND FOLLOW EIA481-1 STANDARD.
ICs MAY ALSO BE MARKED WITH FULL PART NAME: 811L, 811M_...
AMAA or KABB = MAX811L ANAA or KABC = MAX811M APAA or KABD = MAX811T AQAA or KABE = MAX811S ARAA or KABF = MAX811R ASAA or KABG = MAX812L ATAA or KABH = MAX812M AVAA or KABI = MAX812T AWAA or KABJ = MAX812S AXAA or KABK = MAX812R
SOT1434.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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