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19-1421; Rev 1; 4/99
Voltage Detectors
General Description
The MAX6806/MAX6807/MAX6808 precision voltage detectors are ideal for accurate monitoring of power supplies in digital systems. They provide circuit reliability and reduce total cost by eliminating external components and adjustments. The MAX6806/MAX6807/MAX6808 assert a reset signal whenever the supply voltage (VCC) falls below the factorypreset, 2% accurate threshold. Internal hysteresis ensures stable switching. The MAX6806/MAX6807/ MAX6808 are available in 4.6V and 2.6V thresholds (2.3V is also available for the MAX6806 only). The MAX6806 features an active-low, push-pull RESET output; the MAX6807 features an active-high, push-pull RESET output; and the MAX6808 features an active-low, open-drain RESET output. RESET is valid for V CC down to 1V (MAX6806/ MAX6808), and RESET (MAX6807) is guaranteed for VCC down to 1.2V. The MAX6806/MAX6807/MAX6808 are available in 3-pin SC70, 3-pin SOT23, and 4-pin SOT143 packages. The SOT143 package includes a manual-reset input.
Features
o Preset Reset Thresholds: 4.6V and 2.6V (2.3V also available for MAX6806 only) o 2% Accurate Reset Thresholds o Reset Output Available in Active-Low (MAX6806), Active-High (MAX6807), and Open-Drain (MAX6808) Versions o Immune to Power-Supply Transients o RESET Valid to VCC = 1.0V (MAX6806/MAX6808) o 35A Supply Current o No External Components o Manual Reset Available with 4-Pin SOT143 Package o Miniature 3-Pin SC70, 3-Pin SOT23, and 4-Pin SOT143 Packages
MAX6806/MAX6807/MAX6808
Ordering Information
PART MAX6806XR_ _-T MAX6806UR_ _-T MAX6806US_ _-T MAX6807XR_ _-T MAX6807UR_ _-T MAX6807US_ _-T MAX6808XR_ _-T MAX6808UR_ _-T MAX6808US_ _-T TEMP. RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 3 SC70 3 SOT23 4 SOT143 3 SC70 3 SOT23 4 SOT143 3 SC70 3 SOT23 4 SOT143
Applications
Computers Controllers Intelligent Instruments Critical P and C Power Monitoring Portable/Battery-Powered Equipment Automotive Bar-Code Scanners
Typical Operating Circuit and Pin Configurations appear at end of data sheet.
* All devices available in tape-and-reel only, 2500 piece minimum order quantity. Note: Insert the desired number from the Selector Guide into the blank to complete the part number. Also see Selector Guide for top mark.
Selector Guide
PART RESET OUTPUT TOP MARK FZDP FZDQ FZDR KABT KABU KABV NOMINAL VTH- (V) 4.6 2.6 2.3 4.6 2.6 2.3
MAX6806UR46-T MAX6806UR26-T MAX6806UR23-T Active-Low, Push-Pull MAX6806US46-T MAX6806US26-T MAX6806US23-T Other reset thresholds may be available. Contact factory for availability.
Selector Guide continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
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.
Voltage Detectors MAX6806/MAX6807/MAX6808
ABSOLUTE MAXIMUM RATINGS
VCC to GND ..........................................................-0.3V to +6.0V RESET, RESET to GND (MAX6806/MAX6807) ................................-0.3V to (VCC + 0.3V) RESET to GND (MAX6808)...................................-0.3V to + 6.0V MR to GND (SOT143 package only) ....................-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) SOT23, SOT143 (derate 4mW/C above +70C) .........320mW SC70 (derate 2.17mW/C above +70C) .....................174mW 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, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Supply Voltage Range Supply Current SYMBOL VCC ICC CONDITIONS TA = 0C to +70C TA = -40C to +85C VCC = +3.6V, no load VCC = +5.5V, no load MAX680_ _ _46 Reset Threshold VTHTA = +25C, VCC falling TA = +25C, Figure 2 ISINK = 20A, VCC = 1.0V ISINK = 1.0mA, VCC = 2.0V ISOURCE = 2.0mA, VCC = 5.0V (MAX6806 only) VCC = 5.5V, RESET deasserted (MAX6808 only) ISOURCE = 20A, VCC = 1.2V ISOURCE = 400A, VCC = 2.0V ISINK = 3.2mA, VCC = 5.0V VCC falling at 1mV/s RMR VIL VIH VCC > VTH+ 40 0.7VCC 30 30 80 120 0.6 0.8VCC 0.8VCC 0.4 s ppm/C k V V 0.8VCC A MAX680_ _ _26 MAX680_ _ _23 4.508 2.548 2.254 MIN 1.0 1.2 35 50 4.60 2.60 2.30 0.02 VTHTYP MAX 5.5 5.5 60 80 4.692 2.652 2.346 0.03 VTH0.3 0.4 V V V UNITS V A
Reset Threshold Hysteresis
VHYST VOL VOH
RESET Output Voltage (MAX6806/MAX6808)
RESET Output Leakage Current RESET Output Voltage (MAX6807) VCC to Reset Delay (Note 2) Reset Threshold Tempco MR Pull-Down Resistance MR Input Threshold
IOH VOH VOL
Note1: All devices are 100% production tested at TA = +25C, and are guaranteed by design for TA = TMIN to TMAX, as specified. Note 2: RESET output for MAX6806/MAX6808, RESET output for MAX6807.
2
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Voltage Detectors
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
POWER-DOWN RESET DELAY vs. TEMPERATURE
43 41 RESET DELAY (s) 39 37 35 33 31 VCC = 1.0V 29 27 25 -60 -30 0 30 60 90 120 -60 -45 -30-15 0 15 30 45 60 75 90 105 120135 TEMPERATURE (C) TEMPERATURE (C) VOD = VTH- - VCC = 100mV VCC FALLING AT 1mV/S
MAX6806/7/8toc02 MAX6806/7/8-01
MAX6806/MAX6807/MAX6808
SUPPLY CURRENT vs. TEMPERATURE
50 45 40 SUPPLY CURRENT (A) 35 30 25 20 15 10 5 0 VCC = 1.8V VCC = 3.3V VCC = 5.0V 45
POWER-UP RESET DELAY vs. TEMPERATURE
VOD = VCC - VTH+ 11 10 DELAY TIME (s) 9 8 7 6 5 4 -60 -30 0 30 60 90 120 TEMPERATURE (C) VOD = 200mV VOD = 50mV VOD = 100mV
MAX6806/7/8-03
NORMALIZED RESET THRESHOLD vs. TEMPERATURE
1.0080 NORMALIZED RESET THRESHOLD 1.0060 1.0040 1.0020 1.0000 0.9980 0.9960 0.9940 0.9920 0.9900 -40 -30 -15 0 15 30 45 60 75 85 TEMPERATURE (C) VCC FALLING (VTH-) VCC RISING (VTH+)
MAX6806/7/8-04
12
1.0100
Pin Description
PIN NAME SOT23/SC70 SOT143 RESET 1 1 RESET 2 3 -- 4 3 2 GND VCC MR Active-Low Reset Output (MAX6806/MAX6808). RESET remains low while VCC is below the reset-threshold voltage or while MR is held high. Active-High Reset Output (MAX6807). RESET remains high while VCC is below the reset-threshold voltage or while MR is held high. Ground Supply Voltage Input Active-High Manual Reset Input. Internal 80k resistor to GND. FUNCTION
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Voltage Detectors MAX6806/MAX6807/MAX6808
_______________Detailed Description
Reset Output
The MAX6806 voltage detector features an active-low, push-pull RESET output, while the MAX6807 features an active-high, push-pull RESET output. Unlike microprocessor (P) supervisory circuits that offer a reset timeout period, the MAX6806 and MAX6807 RESET goes high and RESET goes low virtually immediately once VCC exceeds the reset threshold. If a brownout occurs (VCC falls below the reset threshold), RESET goes low and RESET goes high. RESET is guaranteed to be a logic low for VCC 1V and RESET is guaranteed to be a logic high for VCC 1.2V. The MAX6808 features an active-low, open-drain RESET output. The output sinks current when VCC falls below the reset threshold. Connect a pull-up resistor from RESET to any supply voltage up to 6V (Figure 1). Select a resistor value large enough to provide a logic low and small enough to provide a logic high while supplying all input and leakage currents connected to the RESET line. A 100k resistor is sufficient in applications driving high-impedance loads. The manual reset input (MR, 4-pin SOT143 package) can also initiate a reset (see Manual Reset Input section).
Manual Reset Input
Many applications require manual-reset capabilities, allowing an operator, a test technician, or external logic circuitry to initiate a reset. A logic high on MR asserts a reset and remains asserted while MR is high. This input has an 80k pull-down resistor, so the input may be left unconnected if not used. Connect a normally open momentary switch from MR to VCC to create a manualreset function. 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 noise immunity.
Hysteresis
The MAX6806/MAX6807/MAX6808 feature internal hysteresis that creates two trip points: one for the rising supply voltage and one for the falling supply voltage (Figure 2). The hysteresis prevents the output from oscillating (chattering) when VCC is near the reset threshold.
Reset Threshold Accuracy
The MAX6806/MAX6807/MAX6808 are ideal for systems using a 5V 5%, 3V 5%, or 2.5V 5% power supply with ICs specified for 5V 10%, 3V 10%, or 2.5V 10%, respectively. 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.
+3.3V
+5.0V VTH+ HYST VHYST = VTH+ - VTH-
VCC
VCC
VTH-
100k
MAX6808
5V SYSTEM RESET (MAX6806/MAX6808)
VOH
RESET
VOL
VOH GND GND RESET (MAX6807)
VOL
Figure 1. The MAX6808 open-drain RESET output allows use with multiple supplies.
4
Figure 2. Input and Output Waveforms with VCC Varied
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Voltage Detectors
Applications Information
Negative-Going VCC Transients In addition to asserting a reset signal during power-up, power-down, and brown-out conditions, the MAX6806/ MAX6807/MAX6808 are immune to short-duration, negative-going VCC transients. Figure 3 displays typical transient durations vs. resetcomparator overdrive for which the MAX6806/MAX6807/ MAX6808 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 further below the reset threshold), the maximum allowable pulse width decreases. A 0.1F capacitor mounted as close as possible to VCC provides additional transient immunity. Ensuring a Valid Reset Output Down to VCC = Ground
When V CC falls below 1V, the MAX6806/MAX6808 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 circuitry is inoperative when VCC is below 1V. In applications where RESET must be valid down to ground, add a pull-down resistor to RESET so any stray leakage currents flow to ground, holding RESET low (Figure 4). Select R1 to be large enough not to load RESET and small enough to pull RESET to ground. For most applications, 100k will not load RESET and will pull RESET to ground. Similarly, if RESET (MAX6807) must be valid below 1.2V, add a pull-up resistor to RESET.
MAX6806/MAX6807/MAX6808
80 TA = +25C MAXIMUM TRANSIENT DURATION (s) 70 60 50 40 MAX680 30 20 10 100 1000 GND RESET COMPARATOR OVERDRIVE, VTH- - VCC (mV) R1 100k GND 46 RESET RESET R1 100k VCC VCC
MAX6806
MAX6807
Figure 3. Maximum Transient Duration without Causing a Reset Pulse vs. Reset Comparator Overdrive
Figure 4. RESET / RESET Valid to VCC = Ground Circuit
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5
Voltage Detectors MAX6806/MAX6807/MAX6808
Interfacing to Ps with Bidirectional Reset Pins
Ps with bidirectional reset pins (such as the Motorola 68HC11 series) can contend with push-pull RESET outputs, resulting in indeterminate logic levels. Use the MAX6808 with the open-drain RESET when interfacing to this type of controller.
VCC VCC VCC
4.7k
MAX6808
P
RESET
RESET
GND
GND
Figure 5. Interfacing to Ps with Bidirectional Reset I/O
Selector Guide (continued)
PART* MAX6806XR46-T MAX6806XR26-T MAX6806XR23-T MAX6807UR46-T MAX6807UR26-T MAX6807US46-T MAX6807US26-T MAX6807XR46-T MAX6807XR26-T MAX6808UR46-T MAX6808UR26-T MAX6808US46-T MAX6808US26-T MAX6808XR46-T MAX6808XR26-T Other reset thresholds may be available. Contact factory for availability. 6 _______________________________________________________________________________________ RESET OUTPUT TOP MARK AAA AAB AAC FZDS FZDT KABW KABX AAD AAE FZDU FZDV KABY KABZ AAF AAG NOMINAL VTH- (V) 4.6 2.6 2.3 4.6 2.6 4.6 2.6 4.6 2.6 4.6 2.6 4.6 2.6 4.6 2.6
Active-Low, Push-Pull
Active-High, Push-Pull
Active-Low, Open-Drain
Voltage Detectors
Pin Configurations
TOP VIEW
MAX6806/MAX6807/MAX6808
(RESET)/RESET (RESET)/RESET 1
1
4
GND
GND 2
MAX6806 MAX6807 MAX6808
3
VCC
MAX6806 MAX6807 MAX6808
MR 2 3 VCC
SOT23/SC70 SOT143
( ) ARE FOR MAX6807
Typical Operating Circuit
VCC VCC VCC
MAX6806 MAX6807 MAX6808
(RESET)/RESET RESET INPUT
P
GND
GND
( ) ARE FOR MAX6807
___________________Chip Information
TRANSISTOR COUNT: 72
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7
Voltage Detectors MAX6806/MAX6807/MAX6808
Package Information
SC70, 3L.EPS
8
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Voltage Detectors
Package Information (continued)
SOTPO3L.EPS
MAX6806/MAX6807/MAX6808
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9
Voltage Detectors MAX6806/MAX6807/MAX6808
Package Information (continued)
SOT1434.EPS
10
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Voltage Detectors
NOTES
MAX6806/MAX6807/MAX6808
11
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Voltage Detectors MAX6806/MAX6807/MAX6808
NOTES
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.
12 ____________________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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