19-1933 Rev 1; 2/01
3-Pin, Low-Power
µP Reset Circuits
General Description
The MAX6800/MAX6801/MAX6802 microprocessor (µP)
supervisory circuits monitor the power supplies in 2.85V
to 5.0V µP and digital systems. They increase circuit
reliability and reduce cost by eliminating external com-
ponents and adjustments.
These devices perform a single function—they assert a
reset signal whenever the V
CC
supply voltage declines
below a preset threshold, keeping it asserted for a preset
timeout period after V
CC
has risen above the reset
threshold. The only difference among the three devices
is their output. The MAX6801 (push/pull) and MAX6802
(open-drain) have an active-low
RESET
output, while the
MAX6800 (push/pull) has an active-high RESET output.
The MAX6800/MAX6801 are guaranteed to be in the cor-
rect state for V
CC
down to 0.7V. The MAX6802 is guaran-
teed to be in the correct state for V
CC
down to 1.0V.
The reset comparator in these ICs is designed to ignore
fast transients on V
CC
. Reset thresholds are factory-
trimmable between 2.63V and 4.80V, in approximately
100mV increments. These devices are available with a
1ms (min), 20ms (min), or 100ms (min) reset pulse
width. Ideal for space-critical applications, the
MAX6800/MAX6801/MAX6802 come packaged in a 3-
pin SOT23. For a lower threshold voltage version, see
the MAX6332/MAX6333/MAX6334.
o
Low 4.0µA Supply Current
o
Precision Monitoring of 2.85V to 5.0V Power-
Supply Voltages
o
Reset Thresholds Available from 2.63V to 4.80V,
in Approximately 100mV Increments
o
Fully Specified over Temperature
o
Three Power-On Reset Timeout Periods Available
(1ms min, 20ms min, 100ms min)
o
Low Cost
o
Three Available Output Structures: Push/Pull
RESET, Push/Pull
RESET,
Open-Drain
RESET
o
Guaranteed RESET/RESET Valid to V
CC
= 0.7V
(MAX6800/MAX6801)
o
Power-Supply Transient Immunity
o
No External Components Required
o
3-Pin SOT23 Package
o
Pin Compatible with MAX809/MAX810,
MAX6326/MAX6327/MAX6328, and
MAX6346/MAX6347/MAX6348
Features
o
Ultra-Low 0.7V Operating Supply Voltage
MAX6800/MAX6801/MAX6802
Applications
Computers
Controllers
Intelligent Instruments
Critical µP/µC Power Monitoring
Portable/Battery-Powered Equipment
Automotive
Ordering Information
PART*
MAX6800UR_
_D_-T
MAX6801UR_
_D_-T
MAX6802UR_
_D_-T
TEMP. RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
3 SOT23-3
3 SOT23-3
3 SOT23-3
Typical Operating Circuit and Pin Configuration appear
at end of data sheet.
Selector Guide appears at end of data sheet.
*These
devices are available in factory-set V
CC
reset thresh-
olds from 2.63V to 4.80V, in approximately 0.1V increments.
Choose the desired reset threshold suffix from Table 1 and
insert it in the blanks following “UR” in the part number.
Factory-programmed reset timeout periods are also available.
Insert the number corresponding to the desired nominal reset
timeout period (1 = 1ms min, 2 = 20ms min, 3 = 100ms min) in
the blank following “D” in the part number. There are 15 stan-
dard versions with a required order increment of 2500 pieces.
Sample stock is generally held on the standard versions only
(see Selector Guide). Contact the factory for availability of non-
standard versions (required order increment is 10,000 pieces).
All devices available in tape-and-reel only.
________________________________________________________________
Maxim Integrated Products
1
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.
3-Pin, Low-Power
µP Reset Circuits
MAX6800/MAX6801/MAX6802
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
V
CC
......................................................................-0.3V to +6V
Push/Pull RESET,
RESET
.......................-0.3V to (V
CC
+ 0.3V)
Open-Drain
RESET
..............................................-0.3V to +6V
Input Current (V
CC
) .............................................................20mA
Output Current (RESET,
RESET).........................................20mA
Continuous Power Dissipation (T
A
= +70°C)
3-Pin SOT23 (derate 4mW/°C above +70°C) ..............320mW
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°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
= full range, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at
V
CC
= +5.0V and T
A
= +25°C, reset not
asserted.) (Note 1)
PARAMETER
Supply Voltage Range
(Note 2)
SYMBOL
CONDITIONS
T
A
= 0°C to +125°C
V
CC
T
A
= -40°C to +125°C
Supply Current
I
CC
No load
MAX6800/MAX6801
MAX6802
MAX6800/MAX6801
MAX6802
V
CC
= +3.0V
V
CC
= +5.0V
T
A
= +25°C
T
A
= -40°C to +125°C
V
CC
Falling Reset Delay
Reset Active Timeout Period
t
RP
V
CC
falling at 10V/ms
MAX680_UR_ _D1-T
MAX680_UR_ _D2-T
MAX680_UR_ _D3-T
RESET
Output Low Voltage
(MAX6801/MAX6802)
RESET
Output High Voltage
(MAX6801)
V
OL
Reset
asserted
Reset not
asserted
Reset
asserted
Reset not
asserted
I
SINK
= 50µA, V
CC
≥
1.0V
I
SINK
= 1.2mA, V
CC
≥
2.5V
I
SINK
= 1.2mA, V
CC
≥
4.25V
I
SOURCE
= 500µA, V
CC
≥
3.0V
I
SOURCE
= 800µA, V
CC
≥
5.0V
I
SOURCE
= 1µA, V
CC
≥
1.0V
I
SOURCE
= 200µA, V
CC
≥
1.8V
I
SOURCE
= 800µA, V
CC
≥
4.25V
I
SINK
= 1.2mA, V
CC
≥
3.0V
I
SINK
= 3.2mA, V
CC
≥
5.0V
0.8 x V
CC
0.8 x V
CC
0.8 x V
CC
0.8 x V
CC
0.8 x V
CC
0.3
0.4
0.5
µA
V
1
20
100
V
TH
- 1.8%
V
TH
- 3%
MIN
0.7
1.0
0.78
1.2
4
5
V
TH
V
TH
30
1.5
30
150
2
40
200
0.4
0.3
0.4
V
V
ms
TYP
MAX
5.5
5.5
5.5
5.5
10
12
V
TH
+ 1.8%
V
V
TH
+ 3%
µs
µA
V
UNITS
Reset Threshold
V
TH
MAX680_UR_ _D_-T,
Table 1
V
OH
RESET Output Voltage
(MAX6800)
V
OH
V
OL
RESET
Output Leakage Current
(MAX6802)
V
CC
> V
TH
,
RESET
not asserted
Note 1:
All parts are production tested at T
A
= +25°C. Overtemperature limits are guaranteed by design and not production tested.
Note 2:
I
SOURCE
for the MAX6800 is I00nA. I
SINK
for the MAX6801 is 100nA. I
SINK
for the MAX6802 is 50µA.
2
_______________________________________________________________________________________
3-Pin, Low-Power
µP Reset Circuits
Typical Operating Characteristics
(Reset not asserted, T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
MAX6800/01/02 toc01
MAX6800/MAX6801/MAX6802
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATURE
MAX6800/01/02 toc02
RESET (V
OL
)
vs. SUPPLY VOLTAGE
+125°C
OUTPUT VOLTAGE LOW (mV)
60
+85°C
40
+25°C
-40°C
20
V
TH
= 2.93V
I
SINK
= 500µA
RESET ASSERTED
MAX6801/MAX6802
MAX6800/01/02 toc03
6.5
6.0
5.5
V
CC
= +5.0V
I
CC
(µA)
5.0
4.5
4.0
3.5
3.0
-50
-25
0
25
50
75
100
V
CC
= +3.3V
1.050
NORMALIZED RESET TIMEOUT PERIOD
1.040
1.030
1.020
1.010
1.000
0.990
0.980
0.970
0.960
0.950
80
0
-50
-25
0
25
50
75
100
125
1.0
1.5
2.0
V
CC
(V)
2.5
3.0
TEMPERATURE (°C)
125
TEMPERATURE (°C)
RESET (V
OH
)
vs. SUPPLY VOLTAGE
MAX6800/01/02 toc04
MAXIMUM TRANSIENT DURATION
vs. RESET COMPARATOR OVERDRIVE
MAX6800/01/02 toc05
V
CC
FALLING PROPAGATION DELAY
vs. TEMPERATURE
90
PROPAGATION DELAY (µs)
80
70
60
50
40
30
20
10
0
V
CC
= FALLING AT 10V/ms
V
CC
= FALLING AT 1V/ms
MAX6800/01/02 toc06
100
OUTPUT VOLTAGE HIGH (V
CC
- V
OH
) (mV)
V
TH
= 2.93V
I
SOURCE
= 100µA
RESET ASSERTED
(MAX6800)
600
MAXIMUM TRANSIENT DURATION (µs)
500
400
300
200
100
0
RESET DOES
NOT OCCUR
RESET OCCURS
100
75
50
+125°C
+85°C
+25°C
25
-40°C
0
1.0
1.5
2.0
V
CC
(V)
2.5
3.0
0.1
100
1000
RESET COMPARATOR OVERDRIVE (mV)
1
10
-50
-25
0
25
50
75
100
125
TEMPERATURE (°C)
Pin Description
PIN
MAX6800
1
—
MAX6801/
MAX6802
1
2
NAME
GND
RESET
Ground
Active-Low Reset Output.
RESET
is asserted while V
CC
is below the reset
threshold and remains asserted for a reset timeout period (t
RP
) after V
CC
rises above the reset threshold.
RESET
on the MAX6801 is push/pull.
RESET
on the MAX6802 is open-drain.
Active-High Reset Output. RESET is asserted while V
CC
is below the reset
threshold and remains asserted for a reset timeout period (t
RP
) after V
CC
rises above the reset threshold. RESET on the MAX6800 is push/pull.
Supply Voltage Input
FUNCTION
2
3
—
3
RESET
V
CC
_______________________________________________________________________________________
3
3-Pin, Low-Power
µP Reset Circuits
MAX6800/MAX6801/MAX6802
Applications Information
Interfacing to µPs with Bidirectional
Reset Pins
Since the
RESET
output on the MAX6802 is open-drain,
this device interfaces easily with µPs that have bidirec-
tional reset pins, such as the Motorola 68HC11.
Connecting the µP supervisor’s
RESET
output directly
to the microcontroller’s (µC’s)
RESET
pin with a single
pullup resistor allows either device to assert reset
(Figure 1).
Negative-Going V
CC
Transients
In addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, these devices are
relatively immune to short-duration, negative-going V
CC
transients (glitches). The
Typical Operating Characteristics
show the Maximum Transient Duration vs. Reset
Comparator Overdrive graph. The graph shows the maxi-
mum pulse width that a negative-going V
CC
transient may
typically have without issuing a reset signal. As the ampli-
tude of the transient increases, the maximum allowable
pulse width decreases.
V
CC
V
CC
100kΩ
V
CC
µP
MOTOROLA
68HCXX
RESET
GND
V
CC
V
CC
100kΩ*
MAX6801
RESET
MAX6800
RESET
MAX6802
RESET
GND
GND
100kΩ
(b)
GND
(a)
Figure 1. Interfacing to µPs with Bidirectional Reset Pins
*ASSUMES HIGH-Z RESET INPUT TO THE
µP
Figure 2. Ensuring Reset Valid Down to V
CC
= 0
Pin Configuration
TOP VIEW
GND
1
V
CC
Typical Operating Circuit
V
CC
V
CC
MAX6800
MAX6801
MAX6802
3
V
CC
MAX6801
RESET
RESET
µP
RESET (RESET)
2
GND
GND
SOT23-3
( ) ARE FOR MAX6800
4
_______________________________________________________________________________________
3-Pin, Low-Power
µP Reset Circuits
Ensuring a Valid Reset Output
Down to V
CC
= 0
When V
CC
falls below 1V and approaches the minimum
operating voltage of 0.7V, push/pull-structured reset
sinking (or sourcing) capabilities decrease drastically.
High-impedance CMOS-logic inputs connected to the
RESET
pin can drift to indeterminate voltages. This
does not present a problem in most cases, since most
µPs and circuitry do not operate when V
CC
drops
below 1V. For the MAX6801 application, where
RESET
must be valid down to 0, adding a pulldown resistor
between
RESET
and GND removes stray leakage cur-
rents, holding
RESET
low (Figure 2a). The pulldown
resistor value is not critical; 100kΩ is large enough not
to load
RESET
and small enough to pull it low. For the
MAX6800 application, where RESET must be valid to
V
CC
= 0, a 100kΩ pullup resistor between RESET and
V
CC
will hold RESET high when V
CC
falls below 0.7V
(Figure 2b).
Since the MAX6802 has an open-drain, active-low out-
put, it typically uses a pullup resistor. With this device,
RESET
will most likely not maintain an active condition,
but will drift to a non-active level due to the pullup
resistor and the reduced sinking capability of the open-
drain device. Therefore, this device is not recommend-
ed for applications where the
RESET
pin is required to
be valid down to V
CC
= 0.
MAX6800/MAX6801/MAX6802
Table 1. Factory-Trimmed Reset Thresholds
RESET
THRESHOLD
SUFFIX
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
T
A
= +25°C
MIN
4.714
4.615
4.547
4.419
4.301
4.223
4.124
4.026
3.928
4.830
3.732
3.633
3.535
3.437
3.339
3.241
3.142
3.025
2.946
2.877
2.750
2.651
2.583
TYP (V
TH
)
4.80
4.70
4.63
4.50
4.38
4.30
4.20
4.10
4.00
3.90
3.80
3.70
3.60
3.50
3.40
3.30
3.20
3.08
3.00
2.93
2.80
2.70
2.63
MAX
4.886
4.785
4.713
4.581
4.459
4.377
4.276
4.174
4.072
3.970
3.868
3.767
3.665
3.563
3.461
3.359
3.258
3.135
3.054
2.983
2.850
2.749
2.677
T
A
= -40°C to +125°C
MIN
4.656
4.559
4.491
4.365
4.249
4.171
4.074
3.977
3.880
3.783
3.686
3.589
3.492
3.395
3.298
3.201
3.104
2.988
2.910
2.842
2.716
2.619
2.551
MAX
4.944
4.841
4.769
4.635
4.511
4.429
4.326
4.223
4.120
4.017
3.914
3.811
3.708
3.605
3.502
3.399
3.296
3.172
3.090
3.018
2.884
2.781
2.709
_______________________________________________________________________________________
5
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