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MAX6468US26D3-T-MAX6468US29D3-T
1.575 V, 150/300 ms, microprocessor supervisory reset circuit with edge-triggered, one-shot manual reset
General DescriptionThe MAX6467/MAX6468 microprocessor (µP) supervi-
sory 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 µP
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 accommo-
date 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 µP platforms.
A single, active-low RESEToutput asserts when VCC
drops below its threshold or if the edge-triggered MR
asserts low. RESETremains low for the reset timeout
period after VCCrises above its threshold and for a fixed,
one-shot timeout period after a manual reset input falling
edge. RESETremains 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 (-40°C to
+125°C) temperature range.
ApplicationsCell Phones/PDAs
Embedded Control Systems
Industrial Equipment
Automotive Products
Portable/Battery-Powered Equipment
Medical Devices
DSL Modems
MP3 Players
GPS Systems
Digital Cameras
FeaturesPrecision Factory-Set Reset Threshold Voltages
for +5.0V, +3.3V, +3.0V, +2.5V, and +1.8V SuppliesEdge-Triggered Manual Reset Input with One-
Shot Pulsed Reset OutputTwo Reset Timeout Period Options (150ms or
1200ms min)Immune to Short Voltage TransientsLow Supply Current (3µA at VCC= +1.8V)RESET
Valid to VCC= +1VActive-Low Open-Drain and Push-Pull RESET
Output Options-40°C to +125°C Operating Temperature RangeSmall 4-Pin SC70 and SOT143 PackagesNo External Components RequiredPin Compatible with MAX811, MAX6315,
MAX6384, and MAX6386
MAX6467/MAX6468
Microprocessor Supervisory Reset Circuits
with Edge-Triggered, One-Shot Manual Reset
Ordering Information19-2523; Rev 0; 7/02
Typical Operating Circuit appears at end of data sheet.
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
MAX6467/MAX6468
Microprocessor Supervisory Reset Circuits
with Edge-Triggered, One-Shot Manual Reset
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICSStresses 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.
VCCto GND...........................................................-0.3V to +6.0V
RESETto GND
Open-Drain........................................................-0.3V to +6.0V
Push-Pull.................................................-0.3V to (VCC+ 0.3V)to GND.................................................-0.3V to (VCC+ 0.3V)
Input/Output Current (all pins)............................................20mA
Continuous Power Dissipation (TA= +70°C)
4-Pin SC70 (derate 3.1mW/°C above +70°C)..............245mW
4-Pin SOT143 (derate 4mW/°C above +70°C).............320mW
Operating Temperature Range.........................-40°C to +125°C
Storage Temperature Range.............................-65°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s).................................+300°C
MAX6467/MAX6468
Microprocessor Supervisory Reset Circuits
with Edge-Triggered, One-Shot Manual Reset
ELECTRICAL CHARACTERISTICS (continued)(VCC= +1.2V to +5.5V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
high (after a valid MRreset assertion). This prevents invalid reset assertion due to switch bounce.
Typical Operating Characteristics(VCC= +5V, MAX6468US29D3 device, TA= +25°C, unless otherwise noted.)
MAX6467/MAX6468
Microprocessor Supervisory Reset Circuits
with Edge-Triggered, One-Shot Manual Reset
Typical Operating Characteristics (continued)(VCC= +5V, MAX6468US29D3 device, TA= +25°C, unless otherwise noted.)
Detailed Description
Reset OutputThe MAX6467 provides an active-low open-drain
RESEToutput. The MAX6468 provides an active-low
push-pull RESEToutput. RESETasserts low if VCC
drops below the selected threshold or if a falling edge
occurs on MR. RESETremains low for the VCCreset
timeout period after VCCincreases above the threshold
voltage or is one-shot pulsed low for the MRtimeout
period after a falling edge on MR.
Manual Reset InputMany µP-based products require manual reset capability,
allowing the operator, a test technician, or external logic
circuitry to initiate a reset. A falling edge on MRasserts
RESETlow. RESETis one-shot pulsed low for the MR
timeout period after a falling edge on MR. An internal
1.5kΩpullup resistor to VCCallows MR to be left uncon-
nected if not used. MRcan be driven with TTL or CMOS-
logic 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 MRand
ignore subsequent falling edges within the reset timeout
period and during the MRdebounce period (see Figure
1). After MRgoes high for 150ms (tDEB), the manual reset
one-shot is ready to trigger a reset on the next MRfalling
edge. Connect a 0.1µF capacitor from MRto GND when
using long cables to provide additional noise immunity
(Figure 2).
MAX6467/MAX6468
Microprocessor Supervisory Reset Circuits
with Edge-Triggered, One-Shot Manual ResetFigure 1. Timing Diagram
MAX6467/MAX6468
Applications Information
Falling VCCTransientsIn addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, the MAX6467/
MAX6468 are relatively immune to short-duration falling
VCCtransients (glitches). The Typical Operating
Characteristicssection shows the Maximum Transient
Duration vs. VCCOverdrive for which the MAX6467/
MAX6468 do not generate a reset pulse. This graph was
generated using a falling pulse applied to VCCstarting
above the actual reset threshold and ending below the
threshold by the magnitude indicated (VCCOverdrive).
The graph indicates the typical maximum pulse width a
falling VCCtransient 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 0.1µF bypass capacitor from
VCCto GND provides additional transient immunity.
Ensuring a Valid RESET Output Down
to VCC= 0VThe 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 RESETremains valid while the RESEToutput 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 RESEToutput
when VCCis above the reset threshold. For most appli-
cations, use 100kΩto 1MΩ.
Microprocessor Supervisory Reset Circuits
with Edge-Triggered, One-Shot Manual ResetFigure 3. RESETValid to VCC= 0V
Chip InformationTRANSISTOR COUNT: 748
PROCESS: BiCMOS
Figure 2. Functional Diagram
