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19-2523; Rev 0; 7/02
Microprocessor Supervisory Reset Circuits with Edge-Triggered, One-Shot Manual Reset
General Description
The MAX6467/MAX6468 microprocessor (P) supervisory circuits monitor single power-supply voltages from +1.8V to +5.0V and assert a reset if the supply voltage drops below its preset threshold. An edge-triggered, one-shot manual reset function ensures that the P enters the reset mode for a fixed timeout period only, even in the event of a continuously asserted manual reset. The MAX6467/MAX6468 significantly improve system reliability compared to traditional manual reset supervisory circuits. A variety of factory-trimmed threshold options accommodate different supply voltages and tolerances, eliminating external components. The factory-set thresholds range from +1.575V to +4.625V to monitor +5.0V, +3.3V, +3.0V, +2.5V, and +1.8V supplies with various tolerances. Reset timeout periods of 150ms (min) and 1200ms (min) are available to accommodate different P platforms. A single, active-low RESET output asserts when VCC drops below its threshold or if the edge-triggered MR asserts low. RESET remains low for the reset timeout period after VCC rises above its threshold and for a fixed, one-shot timeout period after a manual reset input falling edge. RESET remains valid as long as VCC remains above +1V. Open-drain (MAX6467) and push-pull (MAX6468) output options provide additional flexibility in the system design. The MAX6467/MAX6468 are offered in the space-saving 4-pin SOT143 package and the ultra-small 4-pin SC70 package and are specified over the automotive (-40C to +125C) temperature range.
Features
o Precision Factory-Set Reset Threshold Voltages for +5.0V, +3.3V, +3.0V, +2.5V, and +1.8V Supplies o Edge-Triggered Manual Reset Input with OneShot Pulsed Reset Output o Two Reset Timeout Period Options (150ms or 1200ms min) o Immune to Short Voltage Transients o Low Supply Current (3A at VCC = +1.8V) o RESET Valid to VCC = +1V o Active-Low Open-Drain and Push-Pull RESET Output Options o -40C to +125C Operating Temperature Range o Small 4-Pin SC70 and SOT143 Packages o No External Components Required o Pin Compatible with MAX811, MAX6315, MAX6384, and MAX6386
MAX6467/MAX6468
Ordering Information
PART MAX6467XS_ _D_-T MAX6467US_ _D_-T MAX6468XS_ _D_-T MAX6468US_ _D_-T TEMP RANGE -40C to +125C -40C to +125C -40C to +125C -40C to +125C PIN-PACKAGE 4 SC70-4 4 SOT143-4 4 SC70-4 4 SOT143-4
Applications
Cell Phones/PDAs Embedded Control Systems Industrial Equipment Automotive Products Portable/Battery-Powered Equipment Medical Devices DSL Modems MP3 Players GPS Systems Digital Cameras
Note: Insert reset threshold suffix (see Reset Threshold table) after XS or US. Insert reset timeout delay (see Reset Timeout Delay table) after D to complete the part number. Sample stock is generally held on standard versions only (see Standard Versions table). Standard versions have an order increment requirement of 2500 pieces. Nonstandard versions have an order increment requirement of 10,000 pieces. Contact factory for availability.
Pin Configurations
TOP VIEW
GND 1 4 VCC MR
RESET 2
MAX6467XS MAX6468XS
SC70
3
Typical Operating Circuit appears at end of data sheet.
Pin Configurations continued at end of data sheet. 1
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Microprocessor Supervisory Reset Circuits with Edge-Triggered, One-Shot Manual Reset MAX6467/MAX6468
ABSOLUTE MAXIMUM RATINGS
VCC to GND ...........................................................-0.3V to +6.0V RESET to GND Open-Drain........................................................-0.3V to +6.0V Push-Pull.................................................-0.3V to (VCC + 0.3V) MR to GND .................................................-0.3V to (VCC + 0.3V) Input/Output Current (all pins) ............................................20mA Continuous Power Dissipation (TA = +70C) 4-Pin SC70 (derate 3.1mW/C above +70C) ..............245mW 4-Pin SOT143 (derate 4mW/C above +70C).............320mW Operating Temperature Range .........................-40C to +125C Storage Temperature Range .............................-65C to +150C Junction Temperature ......................................................+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 = +1.2V to +5.5V, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Operating Voltage Range SYMBOL VCC CONDITIONS TA = 0C to +125C TA = -40C to 0C VCC = +5.5V, no load Supply Current ICC VCC = +3.6V, no load VCC = +2.5V, no load VCC = +1.8V, no load VCC Reset Threshold (See the Reset Threshold Table) VCC Reset Delay VCC Reset Timeout Period MR Timeout Period MR Rising Debounce Period (Note 2) TA = +25C VTH TA = -40C to +85C TA = +85C to +125C tRD tRP tMRP tDEB VIL MR Input Voltage VIH VIL VIH MR Minimum Input Pulse MR Glitch Rejection MR to RESET Delay MR Pullup Resistance RESET Output High (MAX6468 Only) MR to VCC VCC +2.5V, ISOURCE = 500A, RESET not asserted VOH VCC +4.5V, ISOURCE = 800A, RESET not asserted 750 0.8 x VCC V 0.8 x VCC VCC falling at 10mV/s from VTH + 100mV to VTH - 100mV D3 option D7 option D3 and D7 options D3 and D7 options VTH < +4V VTH +4V 150 1200 150 150 -1.5% -2.5% -3% 35 225 1800 225 225 300 2400 300 300 0.3 x VCC 0.7 x VCC 0.8 2.4 1 100 200 1500 2250 s ns ns V MIN 1.0 1.2 7 6 4 3 VTH TYP MAX 5.5 5.5 13 11 8 7.5 +1.5% +2.5% +3% s ms ms ms V A UNITS V
2
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Microprocessor Supervisory Reset Circuits with Edge-Triggered, One-Shot Manual Reset
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +1.2V to +5.5V, TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER SYMBOL CONDITIONS VCC +1V, ISINK = 80A, RESET asserted RESET Output Low VOL VCC +2.5V, ISINK = 1.2mA, RESET asserted VCC +4.5V, ISINK = 3.2mA, RESET asserted RESET Output Leakage Current (MAX6467 Only) ILKG RESET not asserted MIN TYP MAX 0.3 0.3 0.3 1 A V UNITS
MAX6467/MAX6468
Note 1: Specifications over temperature are guaranteed by design. Production testing at TA = +25C only. Note 2: The MR input ignores falling edges that occur within the MR rising debounce period (tDEB) after MR first rises from low to high (after a valid MR reset assertion). This prevents invalid reset assertion due to switch bounce.
Typical Operating Characteristics
(VCC = +5V, MAX6468US29D3 device, TA = +25C, unless otherwise noted.)
VCC TO RESET DELAY vs. TEMPERATURE
VCC = VTH + 100mV TO VTH - 100mV
MAX6467 toc03
SUPPLY CURRENT vs. TEMPERATURE
MAX6467 toc01
SUPPLY CURRENT vs. SUPPLY VOLTAGE
9 8 SUPPLY CURRENT (A) 7 6 5 4 3 2 1 0 16 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V)
MAX6467 toc02
10 9 8 SUPPLY CURRENT (A) 7 6 5 4 3 2 1 0 VCC = +2.5V VCC = +1.8V VCC = +5.5V VCC = +3.6V
10
26
VCC TO RESET DELAY (s)
24
22
20
18
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
RESET TIMEOUT PERIOD vs. TEMPERATURE
MAX6467 toc04
NORMALIZED RESET THRESHOLD vs. TEMPERATURE
MAX6467 toc05
OUTPUT VOLTAGE LOW vs. SINK CURRENT
VCC = 5.0V
MAX6467 toc06
210 209 RESET TIMEOUT PERIOD (ms) 208 207 206 205 204 203 202 201 200
1.010 NORMALIZED RESET THRESHOLD (V)
600 550 500 450 VOL (mV) 400 350 300 250 200 150 100 50 0
1.005
1.000
0.995
0.990 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
0
1
2
3
4
5
6
7
8
9
10
ISINK (mA)
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3
Microprocessor Supervisory Reset Circuits with Edge-Triggered, One-Shot Manual Reset MAX6467/MAX6468
Typical Operating Characteristics (continued)
(VCC = +5V, MAX6468US29D3 device, TA = +25C, unless otherwise noted.)
OUTPUT VOLTAGE HIGH vs. SOURCE CURRENT
MAX6467 toc07
MAXIMUM TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE
MAXIMUM TRANSIENT DURATION (s)
MAX6467 toc08
5.5 5.0 4.5 4.0 3.5 VOH (V) 3.0 2.5 2.0 1.5 1.0 0.5 0 0 1 2 3 4 5
VCC = +5.0V
600 500 400 300 200 100 0 RESET ASSERTS ABOVE THIS LINE
6
7
8
0
10
20
30
40
50
60
ISOURCE (mA)
RESET THRESHOLD OVERDRIVE (mV)
MR TO RESET DELAY vs. TEMPERATURE
MAX6467 toc09
PROPAGATION DELAY (WITH 100mV OVERDRIVE)
MAX6467 toc10
120 115 110 MR TO RESET DELAY (ns) 105 100 95 90 85 80 75 70 65 60
3.0V VCC 100mV/div AC-COUPLED 2.8V 3V RESET 1V/div
0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) 4s/div
RESET PULLUP AND PULLDOWN RESPONSE
MAX6467 toc11
RESET TIMEOUT PERIOD
MAX6467 toc12
CRESET = 47pF, RPULLUP = 100k, VPULLUP = 1.6V
1.675V VCC 200mV/div 1.475V
3.3V VCC 2V/div 0
1.6V RESET 500mV/div
3.3V RESET 2V/div 0
0 MAX6467_S16D3-T 40s/div 40ms/div
4
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Microprocessor Supervisory Reset Circuits with Edge-Triggered, One-Shot Manual Reset
Pin Description
PIN 1 NAME GND Ground Reset Output. RESET is an active-low open-drain (MAX6467) or push-pull (MAX6468) output. RESET asserts low when VCC drops below the selected threshold and remains low for the VCC reset timeout period after VCC rises above the threshold. The RESET one-shot asserts low for a fixed MR reset timeout period on the falling edge of the manual reset input. The open-drain output requires an external pullup resistor. Manual Reset Input. Drive MR low to initiate a reset output. MR controls an edge-triggered one-shot that asserts RESET low for a fixed MR timeout period when MR is driven low. Internal timing circuitry ignores switch close and open bounce to ensure proper one-shot reset timing. Power-Supply Input. VCC provides power to the device and is also a monitored voltage. When VCC drops below the selected threshold, RESET asserts low and remains low for the reset timeout period after VCC rises above the threshold. For better noise immunity, bypass VCC to GND with a 0.1F capacitor. FUNCTION
MAX6467/MAX6468
2
RESET
3
MR
4
VCC
VCC VTH GND
MR
SWITCH BOUNCE
SWITCH BOUNCE
SWITCH BOUNCE
GND
RESET tRP GND tMRP tDEB tMRP
Figure 1. Timing Diagram
Detailed Description
Reset Output
The MAX6467 provides an active-low open-drain RESET output. The MAX6468 provides an active-low push-pull RESET output. RESET asserts low if V CC drops below the selected threshold or if a falling edge occurs on MR. RESET remains low for the VCC reset timeout period after VCC increases above the threshold voltage or is one-shot pulsed low for the MR timeout period after a falling edge on MR.
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 falling edge on MR asserts
RESET low. RESET is one-shot pulsed low for the MR timeout period after a falling edge on MR. An internal 1.5k pullup resistor to VCC allows MR to be left unconnected if not used. MR can be driven with TTL or CMOSlogic levels, or with open-drain/collector outputs. Connect a normally open momentary pushbutton switch from MR to GND to realize a manual reset function. External debounce circuitry is not required, as the MAX6467/ MAX6468 respond to the first falling edge on MR and ignore subsequent falling edges within the reset timeout period and during the MR debounce period (see Figure 1). After MR goes high for 150ms (tDEB), the manual reset one-shot is ready to trigger a reset on the next MR falling edge. Connect a 0.1F capacitor from MR to GND when using long cables to provide additional noise immunity (Figure 2).
5
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Microprocessor Supervisory Reset Circuits with Edge-Triggered, One-Shot Manual Reset MAX6467/MAX6468
Reset Timeout Delay*
RESET TIMEOUT SUFFIX D3 D7 VCC RESET TIMEOUT PERIOD (min/max) (ms) 150/300 1200/2400 MR TIMEOUT PERIOD (min/max) (ms) 150/300 150/300 MR RISING DEBOUNCE PERIOD (min/max) (ms) 150/300 150/300
*Additional reset timeout options may be available. Contact factory for availability.
Applications Information
Falling VCC Transients In addition to issuing a reset to the P during power-up, power-down, and brownout conditions, the MAX6467/ MAX6468 are relatively immune to short-duration falling V CC transients (glitches). The Typical Operating Characteristics section shows the Maximum Transient Duration vs. V CC Overdrive for which the MAX6467/ MAX6468 do not generate a reset pulse. This graph was generated using a falling pulse applied to VCC starting above the actual reset threshold and ending below the threshold by the magnitude indicated (VCC Overdrive). The graph indicates the typical maximum pulse width a falling VCC transient can have without initiating a reset pulse. As the magnitude of the transient increases (goes
farther below the reset threshold), the maximum allowable pulse width decreases. A 0.1F bypass capacitor from VCC to GND provides additional transient immunity.
Ensuring a Valid RESET Output Down to VCC = 0V
The MAX6467/MAX6468 guarantee proper operation down to VCC = +1V. In applications that require valid reset levels down to VCC = 0V, a pulldown resistor to active-low outputs (MAX6468 only, Figure 3) ensures that RESET remains valid while the RESET output can no longer sink current. This scheme does not work with the open-drain outputs of the MAX6467. Ensure that the resistor value used does not overload the RESET output when VCC is above the reset threshold. For most applications, use 100k to 1M.
VCC 1.5k MR VCC MR ONE-SHOT/ DEBOUNCE MAX6467 MAX6468 VCC
MAX6468
RESET R1 100k
RESET TIMEOUT PERIOD VCC 1.23V
RESET OUTPUT
RESET GND
Figure 3. RESET Valid to VCC = 0V
GND
Chip Information
Figure 2. Functional Diagram
TRANSISTOR COUNT: 748 PROCESS: BiCMOS
6
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Microprocessor Supervisory Reset Circuits with Edge-Triggered, One-Shot Manual Reset MAX6467/MAX6468
Standard Versions
PART MAX6467XS16D3 MAX6467XS22D3 MAX6467XS26D3 MAX6467XS29D3 MAX6467XS46D3 MAX6467US16D3 MAX6467US22D3 MAX6467US26D3 MAX6467US29D3 MAX6467US46D3 MAX6468XS16D3 MAX6468XS22D3 MAX6468XS26D3 MAX6468XS29D3 MAX6468XS46D3 MAX6468US16D3 MAX6468US22D3 MAX6468US26D3 MAX6468US29D3 MAX6468US46D3 TOP MARK AGL AGM AGN AGO AGP KAFN KAFO KAFP KAFQ KAFR AGQ AGR AGS AGC AGB KAFS KAFT KAFU KAEW KAFV
Reset Threshold (-40C to +85C)
SUFFIX 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 VTH (min) 4.509 4.388 4.266 4.193 4.095 3.998 3.900 3.803 3.705 3.608 3.510 3.413 3.315 3.218 3.120 2.998 2.925 2.852 2.730 2.633 2.559 2.438 2.340 2.255 2.133 2.048 1.950 1.853 1.755 1.623 1.536 VTH (typ) 4.625 4.500 4.375 4.300 4.200 4.100 4.000 3.900 3.800 3.700 3.600 3.500 3.400 3.300 3.200 3.075 3.000 2.925 2.800 2.700 2.625 2.500 2.400 2.313 2.188 2.100 2.000 1.900 1.800 1.665 1.575 VTH (max) 4.741 4.613 4.484 4.408 4.305 4.203 4.100 3.998 3.895 3.793 3.690 3.588 3.485 3.383 3.280 3.152 3.075 2.998 2.870 2.768 2.691 2.563 2.460 2.370 2.242 2.153 2.050 1.948 1.845 1.707 1.614
Typical Operating Circuit
+1.0V TO +5.5V
VCC
VCC
MAX6467 MAX6468
MR RESET
RESET INPUT
P
17 16
Pin Configurations (continued)
GND GND
TOP VIEW
GND 1 RESET 2 4 VCC MR
MAX6467US MAX6468US SOT143
3
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7
Microprocessor Supervisory Reset Circuits with Edge-Triggered, One-Shot Manual Reset MAX6467/MAX6468
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.)
8
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Microprocessor Supervisory Reset Circuits with Edge-Triggered, One-Shot Manual Reset
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.)
SC70, 4L.EPS
MAX6467/MAX6468
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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