19-1421; Rev 2; 4/01
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 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 (V
CC
) 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
RESET
output; the MAX6807
features an active-high, push-pull RESET output; and the
MAX6808 features an active-low, open-drain
RESET
out-
put.
RESET
is valid for V
CC
down to 1V (MAX6806/
MAX6808), and RESET (MAX6807) is guaranteed for V
CC
down to 1.2V.
The MAX6806/MAX6807/MAX6808 are available in
3-pin SC70, 3-pin SOT23, 8-pin µMAX, 8-pin SO, 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 V
CC
= 1.0V (MAX6806/MAX6808)
o
35µA 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
o
8 Lead µMAX and 8 Lead SO Packages are Pin
Compatible with the MC33064/MC33164/
MC34064/MC34164
MAX6806/MAX6807/MAX6808
Applications
Computers
Automotive
Controllers
Bar-Code Scanners
Intelligent Instruments
Critical µP and µC Power Monitoring
Portable/Battery-Powered Equipment
Selector Guide and Pin Configurations appear at end of data
sheet.
Ordering Information
PART
MAX6806XR_
_ -T
MAX6806UR_ _ -T
MAX6806US_ _ -T
MAX6806UA_ _
MAX6806SA_ _
MAX6807XR_
_ -T
MAX6807UR_ _ -T
MAX6807US_ _ -T
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
3 SC70
3 SOT23
4 SOT143
8 µMAX
8 SO
3 SC70
3 SOT23
4 SOT143
8 µMAX
8 SO
3 SC70
3 SOT23
4 SOT143
8 µMAX
8 SO
Typical Operating Circuit
V
CC
V
CC
V
CC
MAX6807UA_ _
MAX6807SA_ _
MAX6808XR_
_ -T
MAX6806
MAX6807
MAX6808
(RESET)/RESET
RESET
INPUT
µP
MAX6808UR_ _ -T
MAX6808US_ _ -T
MAX6808UA_ _
MAX6808SA_ _
GND
GND
* SOT23, SOT143, and SC70s are 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 for SOT23
1
( ) ARE FOR MAX6807
________________________________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Voltage Detectors
MAX6806/MAX6807/MAX6808
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ..........................................................-0.3V to +6.0V
RESET,
RESET
to GND
(MAX6806/MAX6807) ................................-0.3V to (V
CC
+ 0.3V)
RESET
to GND (MAX6808)...................................-0.3V to + 6.0V
MR to GND (SOT143 package only) ....................-0.3V to + 6.0V
Input Current, V
CC
...........................................................±20mA
Output Current, RESET,
RESET
.......................................±20mA
Rate of Rise, V
CC
...........................................................100V/µs
Continuous Power Dissipation (T
A
= +70°C)
SOT23, SOT143 (derate 4mW/°C above +70°C) .........320mW
SC70 (derate 2.17mW/°C above +70°C) .....................174mW
µMAX (derate 4.5mW/°C above +70°C) ......................362mW
SO (derate 5.9mW/°C above +70°C) ...........................471mW
Operating Temperature Range ..........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10s) .................................+300°C
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
(V
CC
= +5V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Supply Voltage Range
Supply Current
SYMBOL
V
CC
I
CC
CONDITIONS
T
A
= 0°C to +70°C
T
A
= -40°C to +85°C
V
CC
= +3.6V, no load
V
CC
= +5.5V, no load
MAX680_ _ _46
Reset Threshold
V
TH-
T
A
= +25°C,
V
CC
falling
MAX680_ _ _32
MAX680_ _ _26
MAX680_ _ _23
Reset Threshold Hysteresis
V
HYST
V
OL
V
OH
RESET
Output Leakage Current
RESET Output Voltage
(MAX6807)
V
CC
to Reset Delay (Note 2)
Reset Threshold Tempco
MR Pull-Down Resistance
MR Input Threshold
R
MR
V
IL
V
IH
V
CC
> V
TH+
40
0.7V
CC
I
OH
V
OH
V
OL
T
A
= +25°C, Figure 2
I
SINK
= 20µA, V
CC
= 1.0V
I
SINK
= 1.0mA, V
CC
= 2.0V
I
SOURCE
= 2.0mA, V
CC
= 5.0V
(MAX6806 only)
V
CC
= 5.5V,
RESET
deasserted
(MAX6808 only)
I
SOURCE
= 20µA, V
CC
= 1.2V
I
SOURCE
= 400µA, V
CC
= 2.0V
I
SINK
= 3.2mA, V
CC
= 5.0V
V
CC
falling at 1mV/µs
30
30
80
120
0.6
0.8V
CC
0.8V
CC
0.4
µs
ppm/°C
kΩ
V
V
0.8V
CC
1
µA
4.508
3.136
2.548
2.254
MIN
1.0
1.2
35
50
4.60
3.20
2.60
2.30
0.02
V
TH-
TYP
MAX
5.5
5.5
60
80
4.692
3.264
2.652
2.346
0.03
V
TH-
0.3
0.4
V
V
V
UNITS
V
µA
RESET
Output Voltage
(MAX6806/MAX6808)
Note1:
All devices are 100% production tested at T
A
= +25°C, and are guaranteed by design for T
A
= T
MIN
to T
MAX
, as specified.
Note 2:
RESET
output for MAX6806/MAX6808, RESET output for MAX6807.
2
_______________________________________________________________________________________
Voltage Detectors
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
POWER-DOWN RESET DELAY
vs. TEMPERATURE
43
41
RESET DELAY (µs)
39
37
35
33
31
V
CC
= 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)
V
OD
= V
TH-
- V
CC
= 100mV
V
CC
FALLING AT 1mV/µS
MAX6806/7/8toc02
MAX6806/7/8-01
MAX6806/MAX6807/MAX6808
SUPPLY CURRENT vs. TEMPERATURE
50
45
40
SUPPLY CURRENT (µA)
35
30
25
20
15
10
5
0
V
CC
= 1.8V
V
CC
= 3.3V
V
CC
= 5.0V
45
POWER-UP RESET DELAY vs. TEMPERATURE
V
OD
= V
CC
- V
TH
+
11
10
DELAY TIME (µs)
9
8
7
6
5
4
-60
-30
0
30
60
90
120
TEMPERATURE (°C)
V
OD
= 200mV
V
OD
= 50mV
V
OD
= 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)
V
CC
FALLING (V
TH-
)
V
CC
RISING (V
TH+
)
MAX6806/7/8-04
12
1.0100
Pin Description
PIN
NAME
SOT23/SC70
SOT143
µMAX/SO
RESET
1
1
1
RESET
2
3
—
—
4
3
2
—
4
2
—
3, 5–8
GND
V
CC
MR
N.C.
Active-Low Reset Output (MAX6806/MAX6808).
RESET
remains low while V
CC
is below the reset-threshold voltage or while MR is held high.
Active-High Reset Output (MAX6807). RESET remains high while V
CC
is below
the reset-threshold voltage or while MR is held high.
Ground
Supply Voltage Input
Active-High Manual Reset Input. Internal 80kΩ resistor to GND.
Not Internally Connected
3
FUNCTION
_______________________________________________________________________________________
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 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 V
CC
exceeds the reset threshold. If a brownout
occurs (V
CC
falls below the reset threshold),
RESET
goes low and RESET goes high.
RESET
is guaranteed
to be a logic low for V
CC
≥
1V and RESET is guaran-
teed to be a logic high for V
CC
≥
1.2V.
The MAX6808 features an active-low, open-drain
RESET
output. The output sinks current when V
CC
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 100kΩ 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
sec-
tion).
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 80kΩ pull-down resistor, so the input may be left
unconnected if not used. Connect a normally open
momentary switch from MR to V
CC
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.
Hysteresis
The 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 V
CC
is near the reset threshold.
Reset Threshold Accuracy
The 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.
+3.3V
+5.0V
V
TH+
HYST
V
HYST
= V
TH+
- V
TH-
V
CC
V
CC
V
TH-
100kΩ
MAX6808
5V SYSTEM
RESET
(MAX6806/MAX6808)
V
OH
RESET
V
OL
V
OH
GND
GND
RESET
(MAX6807)
V
OL
Figure 1. The MAX6808 open-drain
RESET
output allows use
with multiple supplies.
4
Figure 2. Input and Output Waveforms with V
CC
Varied
_______________________________________________________________________________________
Voltage Detectors
Applications Information
Negative-Going V
CC
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, neg-
ative-going V
CC
transients.
Figure 3 displays typical transient durations vs. reset-
comparator overdrive for which the MAX6806/MAX6807/
MAX6808 do
not
generate a reset pulse. The graph was
generated using a negative-going pulse applied to V
CC
,
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 V
CC
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 0.1µF
capacitor mounted as close as possible to V
CC
pro-
vides additional transient immunity.
Ensuring a Valid Reset Output Down to
V
CC
= 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 applica-
tions, since most circuitry is inoperative when V
CC
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, 100kΩ 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
T
A
= +25°C
MAXIMUM TRANSIENT DURATION (µs)
70
60
50
40
MAX680
30
20
10
100
1000
GND
RESET COMPARATOR OVERDRIVE, V
TH-
- V
CC
(mV)
R1
100kΩ
GND
46
RESET
RESET
R1
100kΩ
V
CC
V
CC
MAX6806
MAX6807
Figure 3. Maximum Transient Duration without Causing a
Reset Pulse vs. Reset Comparator Overdrive
Figure 4.
RESET
/ RESET Valid to V
CC
= Ground Circuit
_______________________________________________________________________________________
5
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