19-4334; Rev. 7; 12/05
Low-Cost, µP Supervisory Circuits
_______________General Description
The MAX705-MAX708/MAX813L microprocessor (µP)
supervisory circuits reduce the complexity and number
of components required to monitor power-supply and
battery functions in µP systems. These devices signifi-
cantly improve system reliability and accuracy com-
pared to separate ICs or discrete components.
The MAX705/MAX706/MAX813L provide four functions:
1) A reset output during power-up, power-down, and
brownout conditions.
2) An independent watchdog output that goes low if
the watchdog input has not been toggled within 1.6
seconds.
3) A 1.25V threshold detector for power-fail warning,
low-battery detection, or for monitoring a power sup-
ply other than +5V.
4) An active-low manual-reset input.
The MAX707/MAX708 are the same as the MAX705/
MAX706, except an active-high reset is substituted for
the watchdog timer. The MAX813L is the same as the
MAX705, except RESET is provided instead of RESET.
Two supply-voltage monitor levels are available: The
MAX705/MAX707/MAX813L generate a reset pulse when
the supply voltage drops below 4.65V, while the
MAX706/MAX708 generate a reset pulse below 4.40V.
All four parts are available in 8-pin DIP, SO and µMAX
packages.
___________________________Features
♦
µMAX Package: Smallest 8-Pin SO
♦
Guaranteed RESET Valid at V
CC
= 1V
♦
Precision Supply-Voltage Monitor
4.65V in MAX705/MAX707/MAX813L
4.40V in MAX706/MAX708
♦
200ms Reset Pulse Width
♦
Debounced TTL/CMOS-Compatible
Manual-Reset Input
♦
Independent Watchdog Timer—1.6sec Timeout
(MAX705/MAX706)
♦
Active-High Reset Output
(MAX707/MAX708/MAX813L)
♦
Voltage Monitor for Power-Fail or Low-Battery
Warning
MAX705–MAX708/MAX813L
______________Ordering Information
PART
MAX705CPA
MAX705CSA
MAX705CUA
MAX705C/D
TEMP RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
PIN-PACKAGE
8 Plastic DIP
8 SO
8 µMAX
Dice*
_______________________Applications
Computers
Controllers
Intelligent Instruments
Automotive Systems
Critical µP Power Monitoring
Ordering Information continued at end of data sheet.
*
Dice are specified at T
A
= +25°C.
**Contact
factory for availability and processing to MIL-STD-883.
Devices in PDIP, SO and µMAX packages are available in both
leaded and lead-free packaging. Specify lead free by adding
the + symbol at the end of the part number when ordering.
Lead free not available for CERDIP package.
_________________Pin Configurations
TOP VIEW
MR
1
2
8
7
WDO
RESET (RESET)
WDI
PFO
V
CC
__________Typical Operating Circuit
UNREGULATED DC
MAX667
+5V DC LINEAR
REGULATOR
µP
V
CC
PFI
MR
RESET
PFI
MAX705
WDO
MAX706
PFO
V
CC
RESET
I/O LINE
NMI
INTERRUPT
GND
3
PFI
4
MAX705
MAX706
MAX813L
DIP/SO
6
5
MR
V
CC
1
2
8
7
RESET
RESET
N.C.
PFO
GND
3
PFI
4
MAX707
MAX708
6
5
PUSHBUTTON
SWITCH
MAX813L
DIP/SO
( ) ARE FOR MAX813L ONLY.
Pin Configurations continued at end of data sheet.
________________________________________________________________
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.
Low-Cost, µP Supervisory Circuits
MAX705–MAX708/MAX813L
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
V
CC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V
All Other Inputs (Note 1) . . . . . . . . . . . . . . . -0.3V to (V
CC
+ 0.3V)
Input Current
V
CC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20mA
GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20mA
Output Current (all outputs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20mA
Continuous Power Dissipation
Plastic DIP (derate 9.09mW/°C above +70°C) . . . . . . . 727mW
SO (derate 5.88mW/°C above +70°C) . . . . . . . . . . . . . . . 471mW
µMAX (derate 4.10mW/°C above +70°C) . . . . . . . . . . . . 330mW
CERDIP (derate 8.00mW/°C above +70°C) . . . . . . . . . . 640mW
Operating Temperature Ranges
MAX70_C__, MAX813LC__ . . . . . . . . . . . . . . . . . . . . 0°C to +70°C
MAX70_E__, MAX813LE__ . . . . . . . . . . . . . . . . . . . -40°C to +85°C
MAX70_MJA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -55°C to +125°C
Storage Temperature Range . . . . . . . . . . . . . . . . -65°C to +160°C
Lead Temperature (soldering, 10sec) . . . . . . . . . . . . . . . . +300°C
Note 1:
The input voltage limits on PFI and MR can be exceeded if the input current is less than 10mA.
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
= 4.75V to 5.5V for MAX705/MAX707/MAX813L, V
CC
= 4.5V to 5.5V for MAX706/MAX708, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
Operating Voltage Range
SYMBOL
V
CC
CONDITIONS
MAX70_C
MAX813LC
MAX70_E/M, MAX813LE/M
MAX705C, MAX706C, MAX813LC
MAX705E/M, MAX706E/M, MAX813LE/M
MAX707C, MAX708C
MAX707E/M, MAX708E/M
MAX705, MAX707, MAX813L
MAX706, MAX708
MIN
1.0
1.1
1.2
150
150
50
50
4.65
4.40
40
200
TYP
MAX
5.5
5.5
5.5
350
500
350
500
4.75
4.50
280
0.4
0.3
0.3
0.4
V
UNITS
V
Supply Current
I
SUPPLY
µA
Reset Threshold (Note 2)
Reset Threshold Hysteresis (Note 2)
Reset Pulse Width (Note 2)
V
RT
4.50
4.25
140
V
CC
- 1.5
V
mV
ms
t
RS
RESET Output Voltage
RESET Output Voltage
Watchdog Timeout Period
WDI Pulse Width
Low
WDI Input Threshold
High
WDI Input Current
t
WD
t
WP
I
SOURCE
= 800µA
I
SINK
= 3.2mA
MAX70_C, V
CC
= 1V, I
SINK
= 50µA
MAX70_E/M, V
CC
= 1.2V, I
SINK
= 100µA
MAX707, MAX708, I
SOURCE
= 800µA
V
CC
- 1.5
MAX707, MAX708, I
SINK
= 1.2mA
MAX813LC, I
SOURCE
= 4µA, V
CC
= 1.1V
0.8
MAX813LE/M, I
SOURCE
= 4µA, V
CC
= 1.2V
0.9
I
SOURCE
= 800µA
V
CC
- 1.5
MAX813L
I
SINK
= 3.2mA
MAX705, MAX706, MAX813L
1.00
1.60
V
IL
= 0.4V, V
IH
= (V
CC
) (0.8)
50
MAX705, MAX706, MAX813L,
V
CC
= 5V
MAX705, MAX706, MAX813L, WDI = V
CC
MAX705, MAX706, MAX813L, WDI = 0V
MAX705, MAX706, MAX813L,
I
SOURCE
= 800µA
MAX705, MAX706, MAX813L,
I
SINK
= 1.2mA
3.5
-150
V
CC
- 1.5
50
-50
V
0.4
2.25
0.8
150
sec
ns
V
µA
WDO Output Voltage
V
0.4
2
_______________________________________________________________________________________
Low-Cost, µP Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 4.75V to 5.5V for MAX705/MAX707/MAX813L, V
CC
= 4.5V to 5.5V for MAX706/MAX708, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
MR Pull-Up Current
MR Pulse Width
MR Input Threshold
Low
High
t
MD
V
CC
= 5V
I
SOURCE
= 800µA
I
SINK
= 3.2mA
1.20
-25.00
V
CC
- 1.5
0.4
1.25
0.01
t
MR
SYMBOL
MR = 0V
CONDITIONS
MIN
100
150
0.8
2.0
250
1.30
25.00
TYP
250
MAX
600
UNITS
µA
ns
V
ns
V
nA
V
MAX705–MAX708/MAX813L
MR to Reset Out Delay (Note 2)
PFI Input Threshold
PFI Input Current
PFO Output Voltage
Note 2:
Applies to both RESET in the MAX705-MAX708 and RESET in the MAX707/MAX708/MAX813L.
_______________________________________________________________________________________
3
Low-Cost, µP Supervisory Circuits
MAX705–MAX708/MAX813L
__________________________________________Typical Operating Characteristics
MAX705/MAX707
RESET OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
+5V
T
A
= +25°C
1V/div
V
CC
+5V
V
CC
MAX705/MAX707
RESET RESPONSE TIME
POWER-FAIL COMPARATOR
DE-ASSERTION RESPONSE TIME
PFI
+4V
+5V
PFO
V
CC
= +5V
T
A
= +25°C
1k
+3V
T
A
= +25°C
+5V
1V/div
PFO
30pF
+1.25V
0V
V
CC
RESET
V
CC
RESET
GND
0V
500ms/div
2k
+5V
V
CC
1V/div
RESET
V
CC
RESET
GND
10k
RESET
30pF
0V
+1.30V
PFI
0V
+1.20V
400ns/div
RESET
330pF
2µs/div
POWER-FAIL COMPARATOR
ASSERTION RESPONSE TIME
+5V
+5V
PFO
PFI
PFO
30pF
+1.25V
+1.30V
PFI
V
CC
= +5V
T
A
= +25°C
0V
50mV/div
+5V
1k
+5V
1V/div
+1.20V
400ns/div
MAX707
RESET, RESET ASSERTION
V
CC
= V
RT
T
A
= +25°C
+5V
MAX707
RESET, RESET DE-ASSERTION
V
CC
= V
RT
T
A
= +25°C
RESET
0V
V
CC
RESET
RESET
GND
0V
+5V
330pF
RESET
0V
400ns/div
1V/div
10k
10k
330pF
VCC
RESET
RESET
GND
10k
10k
330pF
RESET
2V/div
330pF
RESET
0V
400ns/div
MAX707/MAX708/MAX813L
RESET OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
+5V
T
A
= +25°C
1V/div
V
CC
+5V
V
CC
MAX813L
RESET RESPONSE TIME
+4V
V
CC
RESET
0V
V
CC
RESET
GND
+5V
10k
330pF
1V/div
0V
GND
10k
330pF
+4V
RESET
0V
500ms/div
0V
2µs/div
4
_______________________________________________________________________________________
Low-Cost, µP Supervisory Circuits
MAX705–MAX708/MAX813L
______________________________________________________________Pin Description
PIN
MAX705/MAX706
DIP/SO
µMAX
MAX707/MAX708
DIP/SO
µMAX
MAX813L
DIP/SO
µMAX
Manual-Reset Input triggers a reset pulse when
pulled below 0.8V. This active-low input has an inter-
nal 250µA pull-up current. It can be driven from a TTL
or CMOS logic line as well as shorted to ground with
a switch.
+5V Supply Input
0V Ground Reference for all signals
Power-Fail Voltage Monitor Input. When PFI is less
than 1.25V, PFO goes low. Connect PFI to GND or
V
CC
when not used.
Power-Fail Output goes low and sinks current when
PFI is less than 1.25V; otherwise PFO stays high.
Watchdog Input. If WDI remains high or low for
1.6sec, the internal watchdog timer runs out and
WDO goes low (Figure 1). Floating WDI or connect-
ing WDI to a high-impedance three-state buffer dis-
ables the watchdog feature. The internal watchdog
timer clears whenever reset is asserted, WDI is three-
stated, or WDI sees a rising or falling edge.
No Connect
Active-Low Reset Output pulses low for 200ms when
triggered, and stays low whenever V
CC
is below the
reset threshold (4.65V in the MAX705 and 4.40V in the
MAX706). It remains low for 200ms after V
CC
rises
above the reset threshold or MR goes from low to high
(Figure 3). A watchdog timeout will not trigger RESET
unless WDO is connected to MR.
Watchdog Output pulls low when the internal watch-
dog timer finishes its 1.6sec count and does not go
high again until the watchdog is cleared. WDO also
goes low during low-line conditions. Whenever V
CC
is
below the reset threshold, WDO stays low; however,
unlike RESET, WDO does not have a minimum pulse
width. As soon as V
CC
rises above the reset thresh-
old, WDO goes high with no delay.
Active-High Reset Output is the inverse of RESET.
Whenever RESET is high, RESET is low, and vice
versa (Figure 2). The MAX813L has a RESET output
only.
NAME
FUNCTION
1
3
1
3
1
3
MR
2
3
4
5
2
3
4
5
2
3
4
5
V
CC
GND
4
6
4
6
4
6
PFI
5
7
5
7
5
7
PFO
6
8
-
-
6
8
WDI
-
-
6
-
-
-
N.C.
7
1
7
1
-
-
RESET
8
2
-
-
8
2
WDO
-
-
8
2
7
1
RESET
_______________________________________________________________________________________
5
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