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MAX6806UR26-T-MAX6806US23-T
Voltage Detectors
General DescriptionThe MAX6806/MAX6807/MAX6808 precision voltage
detectors are ideal for accurate monitoring of power
supplies in digital systems. They provide circuit reliabili-
ty and reduce total cost by eliminating external compo-
nents and adjustments.
The MAX6806/MAX6807/MAX6808 assert a reset signal
whenever the supply voltage (VCC) falls below the factory-
preset, ±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 fea-
tures an active-low, push-pull RESEToutput; the MAX6807
features an active-high, push-pull RESET output; and the
MAX6808 features an active-low, open-drain RESETout-
put. RESETis valid for VCCdown 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.
ApplicationsComputers
Controllers
Intelligent Instruments
Critical µP and µC Power Monitoring
Portable/Battery-Powered Equipment
Automotive
Bar-Code Scanners
FeaturesPreset Reset Thresholds: 4.6V and 2.6V
(2.3V also available for MAX6806 only)±2% Accurate Reset ThresholdsReset Output Available in Active-Low (MAX6806),
Active-High (MAX6807), and Open-Drain
(MAX6808) VersionsImmune to Power-Supply TransientsRESET
Valid to VCC= 1.0V (MAX6806/MAX6808)35µA Supply CurrentNo External ComponentsManual Reset Available with 4-Pin SOT143
PackageMiniature 3-Pin SC70, 3-Pin SOT23, and 4-Pin
SOT143 Packages
MAX6806/MAX6807/MAX6808
Voltage Detectors19-1421; Rev 1; 4/99
Selector Guide
Ordering InformationOther reset thresholds may be available. Contact factory for availability.
Typical Operating Circuit and Pin Configurations appear at
end of data sheet.All devices available in tape-and-reel only, 2500 piece mini-
mum 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.
MAX6806/MAX6807/MAX6808
Voltage Detectors
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VCC= +5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
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.
Note1:All devices are 100% production tested at TA = +25°C, and are guaranteed by design for TA= TMINto TMAX, as specified.
Note 2:RESEToutput for MAX6806/MAX6808, RESET output for MAX6807.
VCCto GND ..........................................................-0.3V to +6.0V
RESET, RESETto GND
(MAX6806/MAX6807) ................................-0.3V to (VCC+ 0.3V)
RESETto 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/µs
Continuous Power Dissipation (TA= +70°C)
SOT23, SOT143 (derate 4mW/°C above +70°C) .........320mW
SC70 (derate 2.17mW/°C above +70°C) .....................174mW
Operating Temperature Range ..........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
MAX6806/MAX6807/MAX6808
Voltage Detectors
Typical Operating Characteristics(TA = +25°C, unless otherwise noted.)
Pin Description
MAX6806/MAX6807/MAX6808
Voltage Detectors
_______________Detailed Description
Reset OutputThe MAX6806 voltage detector features an active-low,
push-pull RESEToutput, while the MAX6807 features
an active-high, push-pull RESET output. Unlike micro-
processor (µP) 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. RESETis guaranteed
to be a logic low for VCC ‡1V and RESET is guaran-
teed 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
RESETto 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 100kΩresistor 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 Inputsec-
tion).
Manual Reset InputMany 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 80kΩpull-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 manual-
reset function. If MR is driven from long cables or if the
device is used in a noisy environment, connecting a
0.1µF capacitor from MR to ground provides noise
immunity.
HysteresisThe MAX6806/MAX6807/MAX6808 feature internal hys-
teresis 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 oscil-
lating (chattering) when VCC is near the reset threshold.
Reset Threshold AccuracyThe MAX6806/MAX6807/MAX6808 are ideal for sys-
tems 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 oper-
ating voltage range for the system ICs.
Figure 1. The MAX6808 open-drain RESEToutput allows use
with multiple supplies.
Figure 2. Input and Output Waveforms with VCCVaried
Applications Information
Negative-Going VCCTransientsIn addition to asserting a reset signal during power-up,
power-down, and brown-out conditions, the MAX6806/
MAX6807/MAX6808 are immune to short-duration, neg-
ative-going VCCtransients.
Figure 3 displays typical transient durations vs. reset-
comparator overdrive for which the MAX6806/MAX6807/
MAX6808 do notgenerate a reset pulse. The graph was
generated using a negative-going pulse applied to VCC,
starting 0.5V above the actual reset threshold and end-
ing below it by the magnitude indicated (reset-compara-
tor overdrive). The graph indicates the maximum pulse
width a negative-going VCCtransient 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 0.1µF
capacitor mounted as close as possible to VCCpro-
vides additional transient immunity.
Ensuring a Valid Reset Output Down to
VCC= GroundWhen VCCfalls below 1V, the MAX6806/MAX6808
RESEToutput no longer sinks current—it becomes an
open circuit. Therefore, high-impedance CMOS logic
inputs connected to RESETcan drift to undetermined
voltages. This presents no problem in most applica-
tions, since most circuitry is inoperative when VCCis
below 1V. In applications where RESETmust be valid
down to ground, add a pull-down resistor to RESETso
any stray leakage currents flow to ground, holding
RESETlow (Figure 4). Select R1 to be large enough not
to load RESETand small enough to pull RESETto
ground. For most applications, 100kΩwill not load
RESETand will pull RESETto ground. Similarly, if
RESET (MAX6807) must be valid below 1.2V, add a
pull-up resistor to RESET.
MAX6806/MAX6807/MAX6808
Voltage DetectorsFigure 3. Maximum Transient Duration without Causing a
Reset Pulse vs. Reset Comparator Overdrive
Figure 4. RESET/ RESET Valid to VCC= Ground Circuit
MAX6806/MAX6807/MAX6808
Interfacing to µPs with
Bidirectional Reset PinsµPs with bidirectional reset pins (such as the Motorola
68HC11 series) can contend with push-pull RESETout-
puts, resulting in indeterminate logic levels. Use the
MAX6808 with the open-drain RESETwhen interfacing
to this type of controller.
Voltage DetectorsFigure 5. Interfacing to µPs with Bidirectional Reset I/O
Selector Guide (continued)Other reset thresholds may be available. Contact factory for availability.
