19-0829; Rev 3; 11/05
Microprocessor Supervisory Circuits
General Description
The MAX696/MAX697 supervisory circuits reduce the
complexity and number of components required for
power-supply monitoring and battery-control functions
in microprocessor (µP) systems. These include µP reset
and backup-battery switchover, watchdog timer, CMOS
RAM write protection, and power-failure warning. The
MAX696/MAX697 significantly improve system reliability
and accuracy compared to that obtained with separate
ICs or discrete components.
The MAX696 and MAX697 are supplied in 16-pin pack-
ages and perform six functions:
1) A reset output during power-up, power-down, and
brownout conditions. The threshold for this “low-
line” reset is adjustable by an external voltage-
divider.
2) A reset pulse if the optional watchdog timer has not
been toggled within a specified time.
3) Individual outputs for low-line and watchdog fault
conditions.
4) The reset time may be left at its default value of
50ms, or may be varied with an external capacitor
or clock pulses.
5) A separate 1.3V threshold detector for power-fail
warning, low-battery detection, or to monitor a
power supply other than V
CC
.
The MAX696 also has battery-backup switching for
CMOS RAM, CMOS microprocessor, or other low-
power logic.
The MAX697 lacks battery-backup switching, but has
write-protection pins (CE IN and
CE
OUT) for CMOS
RAM or EPROM. In addition, it consumes less than 250
microamperes.
Features
♦
Adjustable Low-Line Monitor and Power-Down
Reset
♦
Power-OK/Reset Time Delay
♦
Watchdog Timer—100ms, 1.6s, or Adjustable
♦
Minimum Component Count
♦
1µA Standby Current
♦
Battery-Backup Power Switching (MAX696)
♦
On-Board Gating of Chip-Enable Signals
(MAX697)
♦
Separate Monitor for Power-Fail or Low-Battery
Warning
MAX696/MAX697
Ordering Information
PART
MAX696C/D
MAX696CPE
MAX696CWE
MAX696EPE
MAX696EJE
MAX696EWE
MAX696MJE
TEMP RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
Dice
16 PDIP
16 Wide SO
16 PDIP
16 CERDIP
16 Wide SO
16 CERDIP
Ordering Information continued at end of data sheet.
Devices in PDIP and SO packages are available in both lead-
ed 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
Applications
Computers
Controllers
Intelligent Instruments
Automotive Systems
Critical µP Power Monitoring
V
BATT
V
OUT
V
CC
GND
BATT ON
LOW LINE
OSC IN
1
2
3
16
15
14
RESET
RESET
WDO
LLIN
N.C.
WDI
PFO
PFI
MAX696
4
5
6
7
8
13
12
11
10
9
Typical Operating Circuit appears at end of data sheet.
Pin Configurations continued at end of data sheet.
OSC SEL
________________________________________________________________
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.
Microprocessor Supervisory Circuits
MAX696/MAX697
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
V
CC
.......................................................................-0.3V to +6V
V
BATT
....................................................................-0.3V to +6V
All Other Inputs (Note 1).......................-0.3V to (V
OUT
+ 0.5V)
Input Current
V
CC.............................................................................................
200mA
V
BATT............................................................................................
50mA
GND
..............................................................................................
20mA
Output Current
V
OUT .............................................................
Short-Circuit Protected
All Other Outputs
......................................................................
20mA
Rate-of-Rise, V
BATT
, V
CC ........................................................
100V/µs
Operating Temperature Range
C Suffix
..........................................................................
0°C to +70°C
E Suffix
.......................................................................
-40°C to +85°C
M Suffix
....................................................................
-55°C to +125°C
Power Dissipation (T
A
= +70°C)
16-Pin PDIP (derated 7mW/°C above +70°C)
................
600mW
16-Pin SO (derated 7mW/°C above +70°C)
...................
600mW
16-Pin CERDIP (derated 10mW/°C above +85°C)
........
600mW
Storage Temperature Range
..................................
-65°C to +160°C
Lead Temperature (soldering, 10s)
.......................................
+300°C
Note 1:
The input voltage limits on PFI and WDI may be exceeded providing the input current is limited to 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
= full operating range, V
BATT
= 2.8V, T
A
= +25°C, unless otherwise noted.)
PARAMETER
CONDITIONS
MAX696 V
CC
T
A
= full
MAX696 V
BATT
MAX697 V
CC
Supply Current (MAX697)
T
A
= full
V
CC
-
0.3
V
CC
-
0.5
V
BATT
-
0.1
BATTERY-BACKUP SWITCHING (MAX696)
I
OUT
= 1mA, T
A
= full
V
OUT
Output Voltage
I
OUT
= 50mA, T
A
= full
V
OUT
in Battery-Backup Mode
Supply Current (Excludes I
OUT
)
Supply Current in Battery-Backup
Mode
Battery Standby Leakage Current
Battery Switchover Threshold
V
CC
- V
BATT
Battery Switchover Hysteresis
BATT ON Output Voltage
BATT ON Output Short-Circuit
Current
RESET AND WATCHDOG TIMER
Low-Line Voltage Threshold
(LL
IN
)
V
CC
= +5V, +3V; T
A
= full
1.25
1.30
1.35
V
I
SINK
- 1.6mA
BATT ON = V
OUT
= 2.4V sink current
BATT ON = V
OUT
, V
CC
= 0V
7
0.5
2.5
25.0
I
OUT
= 250µA, V
CC
< (V
BATT
- 0.2V), T
A
= full
I
OUT
= 1mA
I
OUT
= 50mA
V
CC
= 0V, V
BATT
= 2.8V, T
A
= +25°C
V
CC
= 0V, V
BATT
= 2.8V, T
A
= full
T
A
= +25°C
5.5V > V
CC
> (V
BATT
+
0.3V)
T
A
= full
Power-up
Power-down
V
CC
-
0.1
V
V
CC
-
0.25
V
BATT
- 0.02
1.5
2.5
0.6
-100
-1.00
70
50
20
0.4
4
7
1
10
+20
+0.02
V
mA
µA
nA
µA
mV
mV
V
mA
µA
MIN
3.0
2.0
3.0
160
TYP
MAX
5.5
V
CC
-
0.3V
5.5
300
µA
UNITS
Operating Voltage Range
V
2
_______________________________________________________________________________________
Microprocessor Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= full operating range, V
BATT
= 2.8V, T
A
= +25°C, unless otherwise noted.)
PARAMETER
Reset Timeout Delay
Watchdog Timeout Period,
Internal Oscillator
Watchdog Timeout Period,
External Clock
Minimum WDI Input Pulse Width
RESET
and RESET Output
Voltage (Note 2)
LOW LINE
and
WDO
Output
Voltage
Output Short-Circuit Current
WDI Input Threshold
CONDITIONS
Figure 6, OSC SEL HIGH, V
CC
= 5V
Long period, V
CC
= 5V
Short period, V
CC
= 5V
Long period
Short period
V
IL
= 0.4V, V
IH
= 3.5V, V
CC
= 5V
I
SINK
= 400µA, V
CC
= 2V, V
BATT
= 0V
I
SINK
= 1.6mA, 3V < V
CC
< 5.5V
I
SOURCE
= 1µA, V
CC
= 5V
I
SINK
= 800µA, T
A
= full
I
SOURCE
= 1µA, V
CC
= 5V, T
A
= full
RESET,
RESET,
WDO, LOW LINE
Logic-low
V
CC
= 5V
(Note 3)
WDI = V
OUT
WDI = 0V
V
CC
= 3V, 5V
V
CC
= 3V, 5V
MAX697
MAX696
I
SINK
= 1.6mA
I
SOURCE
= 1µA, V
CC
= 5V
PFI = 0V,
PFO
= 0V
V
IL
V
IH
, V
CC
= 5V
I
SINK
= 1.6mA
CE
OUT Output Voltage
I
SOURCE
= 800µA
I
SOURCE
= 1µA, V
CC
= 0V
CE
Propagation Delay
OSCILLATOR
OSC IN Input Current
OSC SEL Input Pullup Current
OSC IN Frequency Range
OSC IN Frequency with External
Capacitor
OSC SEL = 0V
OSC SEL = 0V, C
OSC
= 47pF
0
4
±2
5
250
µA
µA
kHz
kHz
V
CC
= 5V
V
CC
-
0.5V
V
CC
-
0.05V
80
150
ns
3.0
3
0.4
V
-50
1.2
Logic-high (MAX696)
Logic-high (MAX697)
WDI Input Current
POWER-FAIL DETECTOR
PFI Input Threshold
PFI - LL
IN
Threshold Difference
PFI Input Current
LL
IN
Input Current
PFO
Output Voltage
PFO
Short-Circuit Source Current
CHIP-ENABLE GATING (MAX697)
CE
IN Thresholds
CE
IN Pullup Current
3.5
3.8
20
-15
1.3
±15
±0.01
±0.01
±0.01
1.4
±50
±25
+25
+25
0.4
25
0.8
50
µA
3.5
1
3
25
0.8
V
3.5
0.4
V
µA
MIN
35
1.00
70
4032
960
200
0.4
0.4
V
TYP
50
1.6
100
MAX
70
2.25
140
4097
1025
UNITS
ms
s
ms
Clock
cycles
ns
MAX696/MAX697
V
mV
nA
nA
V
µA
-25
-500
3.5
1
3
V
µA
Note 2:
T
A
= full operating range.
Note 3:
WDI is guaranteed to be in the mid-level (inactive) state if WDI is floating and V
CC
is in the operating voltage range. WDI is
internally biased to 38% of V
CC
with an impedance of approximately 125kΩ.
_______________________________________________________________________________________
3
Microprocessor Supervisory Circuits
MAX696/MAX697
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
MAX696
SUPPLY CURRENT AS A FUNCTION
OF SUPPLY VOLTAGE
1.50
1.25
SUPPLY CURRENT (mA)
V
CC
MODE
V
CC
MODE
1.00
0.75
0.50
BATTERY MODE
0.25
0
2
3
4
SUPPLY VOLTAGE (V)
5
6
T
A
= 25°C
0.25
0
1.00
0.75
0.50
1.50
1.25
SUPPLY CURRENT (µA)
BATTERY MODE
MAX697
SUPPLY CURRENT AS A FUNCTION
OF SUPPLY VOLTAGE
250
SUPPLY CURRENT (µA)
200
150
100
50
0
2
3
4
SUPPLY VOLTAGE (V)
5
6
T
A
= +25°C
RESET TIMEOUT DELAY AS A
FUNCTION OF SUPPLY VOLTAGE
300
250
RESET TIMEOUT DELAY
(ms)
200
150
100
50
T
A
= +25°C
0
2
3
4
SUPPLY VOLTAGE (V)
5
6
4
_______________________________________________________________________________________
Microprocessor Supervisory Circuits
Pin Description
PIN
MAX696
1
2
3
4
MAX697
—
—
3
5
NAME
V
BATT
V
OUT
V
CC
GND
FUNCTION
Backup-Battery Input. Connect to ground if a backup battery is not used.
The higher of V
CC
or V
BATT
is internally switched to V
OUT
. Connect V
OUT
to V
CC
if
V
OUT
and V
BATT
are not used.
+5V Input
0V Ground Reference for All Signals
BATT ON goes High when V
OUT
is Internally Switched to the V
BATT
Input. It goes low
when V
OUT
is internally switched to V
CC
. The output typically sinks 7mA and can
directly drive the base of an external pnp transistor to increase the output current
above the 50mA rating of V
OUT
.
LOW LINE
goes Low when LL
IN
Falls Below 1.3V. It returns high as soon as LL
IN
rises above 1.3V. See Figure 5.
OSC IN Sets the Reset Delay Timing and Watchdog Timeout Period when OSC SEL
Floats or is Driven Low. The timing can also be adjusted by connecting an external
capacitor to this pin. See Figure 7. When OSC SEL is high, OSC IN selects between
fast and slow watchdog timeout periods
When OSC SEL is Unconnected or Driven High, the Internal Oscillator Sets the Reset
Time Delay and Watchdog Timeout Period. When OSC SEL is low, the external
oscillator input, OSC IN, is enabled. OSC SEL has a 3µA internal pullup. See Table 1.
PFI is the Noninverting Input to the Power-Fail Comparator. When PFI is less than
1.3V,
PFO
goes low. Connect PFI to GND or V
OUT
when not used. See Figure 1.
PFO
is the Output of the Power-Fail Comparator. It goes low when PFI is less than
1.3V. The comparator is turned off and
PFO
goes low when V
CC
is below V
BATT
.
The Watchdog Input, WDI, is a Three-Level Input. If WDI remains either high or low
for longer than the watchdog timeout period,
RESET
pulses low and
WDO
goes low.
The watchdog timer is disabled when WDI is left floating or is driven to mid-supply.
The timer resets with each transition at the watchdog timer input.
No Connection. Leave this pin open.
Low-Line Input. LL
IN
is the CMOS input to a comparator whose other input is a
precision 1.3V reference. The output is
LOW LINE
and is also connected to the reset
pulse generator. See Figure 2.
The Watchdog Output,
WDO,
goes Low if WDI Remains either High or Low for
Longer than the Watchdog Timeout Period.
WDO
is set high by the next transition at
WDI. If WDI is unconnected or at mid-supply,
WDO
remains high.
WDO
also goes
high when
LOW LINE
goes low.
RESET
goes Low whenever LL
IN
Falls Below 1.3V or V
CC
Falls Below the V
BATT
Input Voltage.
RESET
remains low for 50ms after LL
IN
goes above 1.3V.
RESET
also
goes low for 50ms if the watchdog timer is enabled but not serviced within its
timeout period. The
RESET
pulse width can be adjusted as shown in Table 1.
RESET is an Active-High Output. It is the inverse of
RESET.
MAX696/MAX697
5
—
BATT ON
6
6
LOW LINE
7
7
OSC IN
8
8
OSC SEL
9
10
9
10
PFI
PFO
11
11
WDI
12
13
2
4
N.C.
LL
IN
14
14
WDO
15
15
RESET
16
16
RESET
_______________________________________________________________________________________
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