19-1946; Rev 1; 2/01
4-Pin, Low-Power
µP Reset Circuits with Manual Reset
General Description
The MAX6803/MAX6804/MAX6805 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. They also feature a
debounced manual reset input.
These devices perform a single function: they assert a
reset signal whenever the V
CC
supply voltage declines
below a preset threshold or whenever manual reset is
asserted. Reset remains asserted for a preset timeout
period after V
CC
has risen above the reset threshold or
after manual reset is deasserted. The only difference
among the three devices is their output. The MAX6804
(push/pull) and MAX6805 (open-drain) have an active-
low
RESET
output, while the MAX6803 (push/pull) has
an active-high RESET output. The MAX6803/MAX6804
are guaranteed to be in the correct state for V
CC
down
to 0.7V. The MAX6805 is guaranteed to be in the cor-
rect 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 timeout period.
Ideal for space-critical applications, the MAX6803/
MAX6804/MAX6805 come packaged in a 4-pin
SOT143. For a lower threshold voltage version, see the
MAX6335/MAX6336/MAX6337.
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
Debounced Manual Reset Input
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
(MAX6803/MAX6804)
o
Power-Supply Transient Immunity
o
No External Components Required
o
4-Pin SOT143 Package
o
Pin Compatible with MAX811/MAX812 and
MAX6314/MAX6315
Features
o
Ultra-Low 0.7V Operating Supply Voltage
MAX6803/MAX6804/MAX6805
Applications
Computers
Controllers
Intelligent Instruments
Critical µP/µC Power Monitoring
Portable/Battery-Powered Equipment
Automotive
PART*
MAX6803US_
_D_-T
MAX6804US_
_D_-T
MAX6805US_
_D_-T
Ordering Information
TEMP. RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
4 SOT143
4 SOT143
4 SOT143
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 “US” 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.
4-Pin, Low-Power
µP Reset Circuits with Manual Reset
MAX6803/MAX6804/MAX6805
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
V
CC
......................................................................-0.3V to +6V
Push/Pull RESET or
RESET, MR
............-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)
4-Pin SOT143 (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 1)
SYMBOL
CONDITIONS
T
A
= 0°C to +125°C
V
CC
T
A
= -40°C to +125°C
Supply Current
I
CC
No load
MAX6803/MAX6804
MAX6805
MAX6803/MAX6804
MAX6805
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
MR
Minimum Pulse Width
MR
Glitch Immunity
MR
Reset Delay
MR
Input Voltage
MR
Pullup Resistance
RESET
Output Low Voltage
(MAX6804/MAX6805)
RESET
Output High Voltage
(MAX6804)
V
OL
Reset
asserted
Reset not
asserted
I
SINK
= 50µA, V
CC
≥
1.0V
I
SINK
= 1.2mA, V
CC
≥
2.5V
I
SINK
= 3.2mA, V
CC
≥
4.25V
I
SOURCE
= 500µA, V
CC
≥
3.0V
I
SOURCE
= 800µA, V
CC
≥
5.0V
0.8
✕
V
CC
0.8
✕
V
CC
V
IL
V
IH
0.7
✕
V
CC
12
20
30
0.4
0.3
0.4
V
V
t
RP
V
CC
falling at 10V/ms
MAX680_US_ _D1-T
MAX680_US_ _D2-T
MAX680_US_ _D3-T
1
20
100
1
50
0.1
0.3
✕
V
CC
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
µs
ns
µs
V
kΩ
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_US_ _D_-T,
Table 1
V
OH
2
_______________________________________________________________________________________
4-Pin, Low-Power
µP Reset Circuits with Manual Reset
ELECTRICAL CHARACTERISTICS (continued)
(
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
SYMBOL
V
OH
Reset
asserted
Reset not
asserted
CONDITIONS
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
MIN
0.8
✕
V
CC
0.8
✕
V
CC
0.8
✕
V
CC
0.3
0.4
0.5
V
µA
V
TYP
MAX
UNITS
MAX6803/MAX6804/MAX6805
RESET Output Voltage
(MAX6803)
V
OL
RESET
Output Leakage Current
(MAX6805)
V
CC
> V
TH
,
RESET
not asserted
Note 1:
All parts are production tested at T
A
= +25°C. Over temperature limits are guaranteed by design and not production tested.
Note 2:
I
SOURCE
for the MAX6803 is 100nA; I
SINK
for the MAX6804 is 100nA; I
SINK
for the MAX6805 is 50µA.
__________________________________________Typical Operating Characteristics
(Reset not asserted, T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
MAX6803/04/05 toc01
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATURE
MAX6803/04/05 toc02
OUTPUT VOLTAGE LOW
vs. SUPPLY VOLTAGE
V
TH
= 2.93V
I
SINK
= 500µA
RESET
+125°C
40
+85°C
+25°C
-40°C
20
MAX6803/04/05 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
OUTPUT VOLTAGE LOW (mV)
60
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)
OUTPUT VOLTAGE HIGH
vs. SUPPLY VOLTAGE
OUTPUT VOLTAGE HIGH (V
CC
- V
OH
) (mV)
MAXIMUM TRANSIENT DURATION (µs)
V
TH
= 2.93V
I
SINK
= 100µA
RESET ASSERTED
(MAX6803)
MAX6803/04/05 toc04
MAXIMUM TRANSIENT DURATION
vs. RESET COMPARATOR OVERDRIVE
MAX6803/04/05 toc05
V
CC
FALLING PROPAGATION DELAY
vs. TEMPERATURE
90
POROPAGATION DELAY (µs)
80
70
60
50
40
30
20
10
0
V
CC
= FALLING AT 10V/ms
V
CC
= FALLING AT 1V/ms
MAX6803/04/05 toc06
100
600
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)
_______________________________________________________________________________________
3
4-Pin, Low-Power
µP Reset Circuits with Manual Reset
MAX6803/MAX6804/MAX6805
Pin Description
PIN
MAX6803
1
MAX6804
MAX6805
1
NAME
GND
Ground
Active-Low Reset Output.
RESET
is asserted while V
CC
is below the reset
threshold, or while
MR
is asserted.
RESET
remains asserted for a reset
timeout period (t
RP
) after V
CC
rises above the reset threshold or
MR
is
deasserted.
RESET
on the MAX6804 is push/pull.
RESET
on the MAX6805
is open-drain.
Active-High Reset Output. RESET is asserted high while V
CC
is below the
reset threshold or while
MR
is asserted, and RESET remains asserted for a
reset timeout period (t
RP
) after V
CC
rises above the reset threshold or
MR
is deasserted. RESET on the MAX6803 is push/pull.
Manual Reset Input. A logic low on
MR
asserts reset. Reset remains
asserted as long as
MR
is low, and for the reset timeout period (t
RP
) after
MR
goes high. Leave unconnected or connect to V
CC
if not used.
Supply Voltage Input
FUNCTION
—
2
RESET
2
—
RESET
3
4
3
4
MR
V
CC
Applications Information
Manual Reset Input
Many µP-based products require manual reset capabil-
ity, allowing the operator, a test technician, or external
logic circuitry to initiate a reset. A logic low on
MR
asserts reset. Reset remains asserted while
MR
is low,
and for the reset active timeout period after
MR
returns
high.
MR
has an internal 20kΩ pullup resistor, so it can
be left unconnected if not used. Connect a normally
open momentary switch from
MR
to GND to create a
manual reset function; external debounce circuitry is
not required.
shows the maximum pulse width that a negative-going
V
CC
transient may typically have without issuing a reset
signal. As the amplitude of the transient increases, the
maximum allowable pulse width decreases.
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
V
CC
V
CC
100kΩ
V
CC
µP
MOTOROLA
68HCXX
RESET
Interfacing to µPs with
Bidirectional Reset Pins
Since the
RESET
output on the MAX6805 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).
MAX6805
MR
RESET
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
4
GND
GND
Figure 1. Interfacing to µPs with Bidirectional Reset Pins
_______________________________________________________________________________________
4-Pin, Low-Power
µP Reset Circuits with Manual Reset
µPs and circuitry do not operate when V
CC
drops below
1V. For the MAX6804 application where
RESET
must be
valid down to 0, adding a pulldown resistor between
RESET
and GND removes stray leakage currents, hold-
ing
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 MAX6803, 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 MAX6805 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.
MAX6803/MAX6804/MAX6805
V
CC
Pin Configuration
TOP VIEW
MAX6804
MR
RESET
GND
1
4
V
CC
(a)
GND
100kΩ
MAX6803
MAX6804
MAX6805
V
CC
RESET (RESET)
2
3
MR
100kΩ*
MAX6803
MR
RESET
( ) ARE FOR MAX6803
SOT143
(b)
GND
*ASSUMES HIGH-Z RESET INPUT TO THE
µP
Typical Operating Circuit
V
CC
Figure 2. Ensuring Reset Valid down to V
CC
= 0
V
CC
V
CC
MAX6804
MR
RESET
RESET
µP
GND
GND
PUSHBUTTON
SWITCH
_______________________________________________________________________________________
5
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