19-4000; Rev 2; 8/09
High-Voltage Watchdog Timers with
Adjustable Timeout Delay
General Description
The MAX16997/MAX16998 are microprocessor (µP)
supervisory circuits for high-input-voltage and low-qui-
escent-current applications. These devices detect
downstream circuit failures and provide switchover to
redundant circuitry. See the
Selector Guide
for the dif-
ferent versions of this product family.
The MAX16997/MAX16998 family has four independent
inputs for reset and watchdog functions. SWT and SRT
inputs independently set the timeout periods of watch-
dog and reset timers through external capacitors.
RESETIN/EN monitor voltages at respective inputs. A
resistive voltage-divider sets the reset threshold.
The MAX16998A/B/D generate two output signals,
RESET
and
ENABLE. RESET
asserts whenever
RESETIN drops below its threshold voltage or when the
watchdog timer detects a timing fault at WDI. Once
asserted, and after all reset conditions are removed,
RESET
remains low for the reset timeout period, t
RESET
,
and then goes high. The MAX16997A generates one
output signal (ENABLE) based on the voltage level at
EN and the signal at WDI.
The MAX16997A does not have a
RESET
output. The
watchdog is disabled if the voltage at EN is below its
threshold. The MAX16997A watchdog timer starts tim-
ing when the voltage at EN becomes higher than the
preset threshold voltage level. Each time EN rises
above the preset threshold voltage, the initial watchdog
timeout period is 8 times the normal watchdog timeout
period (t
WP
).
The MAX16997/MAX16998 are available in 8-pin lead-
free µMAX
®
packages and are fully specified over the
-40°C to +125°C automotive temperature range.
o
Wide 5V to 40V Input Voltage Range
o
18µA Quiescent Current (Typical at +125°C)
o
Capacitor-Adjustable Timeout Period for
Watchdog and Reset
o
Windowed Watchdog Timer Options
(MAX16998B/D)
o
External Voltage Monitoring (RESETIN for the
MAX16998A/B/D and EN for the MAX16997A)
o
Car Battery-Compatible EN Input
o
TTL- and CMOS-Compatible Open-Drain Outputs
o
18V Maximum Open-Drain Reset Output Voltage
o
28V Maximum Open-Drain Enable Output Voltage
o
Power-On/Power-Off Reset Functionality
(MAX16998A/B/D Only)
o
AEC-Q100 Qualified
o
-40°C to +125°C Operating Temperature Range
o
Small (3mm x 3mm)
µMAX
Package
o
WDI Narrow Pulse Immunity
Features
MAX16997/MAX16998
Ordering Information
PART
MAX16997AAUA+
MAX16997AAUA/V+
MAX16998AAUA+
MAX16998AAUA/V+
MAX16998BAUA+
MAX16998BAUA/V+
MAX16998DAUA+
MAX16998DAUA/V+
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
8 µMAX
8 µMAX
8 µMAX
8 µMAX
8 µMAX
8 µMAX
8 µMAX
8 µMAX
Applications
Automotive
Industrial
+Denotes a lead(Pb)-free/RoHS-compliant package.
/V Denotes Automotive qualified part.
Selector Guide
PART
MAX16997A
MAX16998A
MAX16998B
MAX16998D
WATCHDOG
WINDOW SIZE (%)
100
100
50
75
ENABLE
✓
✓
✓
✓
RESET
—
✓
✓
✓
EN
✓
—
—
—
RESETIN
—
✓
✓
✓
Pin Configurations appear at end of data sheet.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
High-Voltage Watchdog Timers with
Adjustable Timeout Delay
MAX16997/MAX16998
ABSOLUTE MAXIMUM RATINGS
(All pins referenced to GND, unless otherwise noted.)
IN,
ENABLE
............................................................-0.3V to +45V
WDI,
RESET,
EN .....................................................-0.3V to +20V
RESETIN .................................................................-0.3V to +20V
SRT, SWT................................................................-0.3V to +12V
Maximum Current (all pins).................................................30mA
Continuous Power Dissipation (T
A
= +70°C)
8-Pin µMAX (derate 4.8mW/°C above +70°C) ..........387.8mW
Junction-to-Case Thermal Resistance (θ
JC
) (Note 1) ......42°C/W
Junction-to-Ambient Thermal Resistance (θ
JA
) (Note 1).....206.3°C/W
Operating Temperature Range (T
A
) ..................-40°C to +125°C
Junction Temperature (T
J
) ...............................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Note 1:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to
www.maxim-ic.com/thermal-tutorial.
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
IN
= 14V, T
A
= T
J
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
Operating Voltage Range
Supply Current
SWT Ramp Current
SRT Ramp Current
SWT/SRT Ramp Threshold
Voltage
RESET TIMER
Power-On Reset Input Threshold
Voltage
RESETIN Input Leakage Current
RESET
Output Low Voltage
RESET
Leakage Current
ENABLE
Output Low Voltage
ENABLE
Leakage Current
Minimum Reset Timeout Period
Reset Timeout Period
Maximum Reset Time Period
RESET
to
ENABLE
Delay
RESETIN to
RESET
Delay
V
PON
I
LPON
V
OLRST
I
LKGR
V
OLEN
I
LKGE
t
RESETmin
t
RESET
t
RESETmax
t
REDL
t
RRDL
RESETIN falling below V
PON
to
RESET
falling edge
V
RESETIN
rising
V
RESETIN
falling
V
RESETIN
= 2V
RESET
asserted, I
SINK
= 1mA
V
IN
= 1.1V, I
SINK
= 160µA,
RESET
asserted
RESET
asserted, I
SINK
= 0.4mA
V
RESET
= 20V,
RESET
not asserted
ENABLE
asserted, I
SINK
= 5mA
V
ENABLE
= 14V,
ENABLE
not asserted
C
SRT
= 390pF (Note 3)
C
SRT
= 2000pF (Note 3)
C
SRT
= 47nF
0.1
1
5
116.09
1.5
1
0.1
0.4
1.135
1.115
1.255
1.235
0.1
0.9
0.4
0.4
µA
V
µA
ms
ms
ms
µs
µs
V
1.383
1.363
V
µA
SYMBOL
V
IN
I
IN
T
A
= -40°C to +85°C
T
A
= -40°C to +125°C
450
410
1.115
CONDITIONS
MIN
5.0
18
18
500
500
1.235
TYP
MAX
40.0
30
60
550
600
1.363
UNITS
V
µA
nA
nA
V
I
RAMP_SWT
V
SWT
= 1.0V
I
RAMP_SRT
V
SRT
= 1.0V
V
RAMP
2
_______________________________________________________________________________________
High-Voltage Watchdog Timers with
Adjustable Timeout Delay
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 14V, T
A
= T
J
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
WATCHDOG TIMER
WDI Input Threshold
WDI Input Hysteresis
WDI Minimum Pulse Width
WDI Input Current
Minimum Watchdog Timeout
Watchdog Timeout Period
Maximum Watchdog Timeout
Watchdog Window
WDI to
ENABLE
Output Delay
RESET
Pullup Resistor Supply
Voltage
ENABLE
Pullup Resistor Supply
Voltage
V
IH
V
IL
WDI
HYST
t
WDImin
I
WDI
t
WPmin
t
WP
t
WPmax
D
WDI
(Note 4)
WDI = 0 or 14V
C
SWT
= 680pF (Note 3)
C
SWT
= 1200pF (Note 3)
C
SWT
= 22nF
MAX16998B
MAX16998D
Start from WDI third wrong trigger
(Note 5)
2.25
45
67.5
6.5
0.1
6.8
12
217.36
50
75
100
2.5
18.00
55
82.5
200
2.25
0.9
V
mV
µs
µA
ms
ms
ms
%t
WP
µs
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX16997/MAX16998
(Note 5)
2.25
2.5
28.00
V
Note 2:
R
RESET
and R
ENABLE
are external pullup resistors for open-drain outputs. Connect R
RESET
and R
ENABLE
to a minimum 2.5V
voltage. Connect R
RESET
to a maximum voltage of 18V and connect R
ENABLE
to a maximum voltage of 28V.
Note 3:
Calculated based on V
RAMP
= 1.235V and I
RAMP
= 500nA.
Note 4:
WDI pulses narrower than 1µs will be ignored. WDI pulses wider than 6.5µs will be recognized.
Note 5:
Not production tested, guaranteed by design.
Typical Operating Characteristics
(C
SWT
= C
SRT
= 1500pF, T
A
= +25°C, unless otherwise noted.)
RESET TIMEOUT PERIOD
vs. C
SRT
MAX16997/98 toc01
WATCHDOG TIMEOUT PERIOD
vs. C
SWT
MAX16997/98 toc02
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
24
SUPPLY CURRENT (µA)
22
20
18
16
14
12
RESET AND ENABLE NOT
ASSERTED
MAX16997/98 toc03
10,000
I
RAMP
= 500nA
10,000
WATCHDOG TIMEOUT PERIOD (ms)
I
RAMP
= 500nA
26
RESET TIMEOUT PERIOD (ms)
1000
1000
100
100
10
10
1
0.1
0.1
1
10
C
SRT
(nF)
100
1000
1
0.1
1
10
C
SWT
(nF)
100
1000
10
0
10
20
30
40
50
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
3
High-Voltage Watchdog Timers with
Adjustable Timeout Delay
MAX16997/MAX16998
Typical Operating Characteristics (continued)
(C
SWT
= C
SRT
= 1500pF, T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. TEMPERATURE
MAX16997/98 toc04
RESETIN/EN THRESHOLD VOLTAGE
vs. TEMPERATURE
MAX16997/98 toc05
RESETIN/EN THRESHOLD VOLTAGE
vs. SUPPLY VOLTAGE
RESETIN/EN THRESHOLD VOLTAGE (V)
1.45
1.40
1.35
1.30
1.25
1.20
1.15
1.10
1.05
1.00
FALLING
RISING
MAX16997/98 toc06
20.0
19.5
19.0
SUPPLY CURRENT (µA)
18.5
18.0
17.5
17.0
16.5
16.0
15.5
15.0
RESET AND ENABLE NOT
ASSERTED
1.35
RESETIN/EN THRESHOLD VOLTAGE (V)
1.33
1.30
1.28
1.25
1.23
1.20
1.18
1.15
1.13
1.10
FALLING
RISING
1.50
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
4
8
12
16
20
24
28
32
36
40
SUPPLY VOLTAGE (V)
RESETIN TO RESET DELAY
vs. TEMPERATURE
MAX16997/98 toc07
RESETIN/WATCHDOG PERIOD
vs. SUPPLY VOLTAGE
MAX16997/98 toc08
RESETIN/WATCHDOG PERIOD
vs. SUPPLY VOLTAGE
RESET/WATCHDOG TIMEOUT PERIOD (ms)
100
90
80
70
60
50
40
30
20
10
4
8
12
16
20
24
28
32
36
40
RESET TIMEOUT
PERIOD (C
SRT
= 10nF)
WATCHDOG TIMEOUT
PERIOD (C
SWT
= 10nF)
MAX16997/98 toc09
2.00
1.75
RESETIN TO RESET DELAY (µs)
1.50
1.25
1.00
0.75
0.50
0.25
0
50mV OVERDRIVE
100mV OVERDRIVE
RESETIN FROM 2V TO 0V
8
RESET/WATCHDOG TIMEOUT PERIOD (ms)
7
6
5
4
3
2
1
0
4
8
12
16
20
24
28
32
36
RESET TIMEOUT
PERIOD (C
SRT
= 680pF)
WATCHDOG TIMEOUT
PERIOD (C
SWT
= 680pF)
110
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
40
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
I
RAMP
vs. TEMPERATURE
MAX16997/98 toc10
RESET OUTPUT VOLTAGE
vs. SINK CURRENT
0.9
RESET OUTPUT VOLTAGE (V)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
MAX16997/98 toc11
ENABLE OUTPUT VOLTAGE
vs. SINK CURRENT
0.7
ENABLE OUTPUT VOLTAGE (V)
0.6
0.5
0.4
0.3
0.2
0.1
0
0
5
10
15
20
25
30
MAX16997/98 toc12
520
515
510
505
I
RAMP
(nA)
500
495
490
485
480
475
470
1.0
0.8
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
0
0.5
1.0
1.5
2.0
2.5
3.0
SINK CURRENT (mA)
SINK CURRENT (mA)
4
_______________________________________________________________________________________
High-Voltage Watchdog Timers with
Adjustable Timeout Delay
Pin Description
PIN
MAX16997A
1
2
3, 7
MAX16998A/B/D
1
—
—
NAME
IN
EN
N.C.
FUNCTION
Power-Supply Input. Bypass IN to GND with a 0.1µF capacitor.
High-Impedance Input to the Enable Comparator. Depending on the voltage level
at EN, the internal watchdog timer is turned on or off (see the
EN Input
section).
No Connection. Not internally connected.
Watchdog Timeout Adjustment Input. Connect a capacitor between SWT and GND
to set the basic watchdog timeout period. Connect SWT to ground to disable the
watchdog timer function. See the
Selecting the Watchdog Timeout Capacitor
section.
Ground
Watchdog Input.
MAX16997A/MAX16998A (Timeout Watchdog):
Two consecutive WDI falling
edges must occur at WDI within the watchdog timeout period or
RESET
asserts.
The watchdog timer clears when a falling edge occurs on WDI or whenever
RESET
is asserted.
ENABLE
asserts if three consecutive watchdog timeout periods have
expired without a falling edge at WDI. WDI is a high-impedance input. Leaving
WDI unconnected will cause improper operation of the watchdog timer.
MAX16998B/D (Window Watchdog):
WDI falling transitions within periods shorter
than the closed window width or longer than the basic watchdog timeout period
force
RESET
to assert low for the reset timeout period. The watchdog timer begins
to count after
RESET
is deasserted. The watchdog timer clears when a WDI falling
edge occurs or whenever
RESET
is asserted.
ENABLE
asserts if three consecutive
watchdog timeout periods have expired without a falling edge at WDI. WDI is a
high-impedance input. Leaving WDI unconnected will cause improper operation of
the watchdog timer.
Open-Drain Enable Output.
ENABLE
asserts when three consecutive WDI faults
occur.
ENABLE
remains low until three consecutive good WDI falling edges occur.
ENABLE
does not assert if the voltage at RESETIN (EN) is below its threshold.
These devices are guaranteed to be in correct
ENABLE
output logic state when
V
IN
remains greater than 1.1V.
Reset Input. High-impedance input to the reset comparator. When V
RESETIN
falls
below 1.235V,
RESET
asserts.
RESET
remains asserted as long as V
RESETIN
is low
and for the reset timeout period after RESETIN goes high. Connect V
RESETIN
to the
center point of an external resistive divider to set the threshold for the externally
monitored voltage. Connect RESETIN to a defined voltage logic-level.
Reset Timeout Adjustment Input. Connect a capacitor between SRT and GND to
set the reset timeout period. See the
Selecting the Reset Timeout Capacitor
section.
Open-Drain Reset Output.
RESET
asserts whenever RESETIN drops below the
selected reset threshold voltage (V
PON
).
RESET
remains low for the reset timeout
period after all reset conditions are removed, and then goes high.
RESET
asserts
for a period of t
RESET
whenever a WDI fault occurs. Connect
RESET
to a pullup
resistor connected to a voltage higher than 2.5V (typ).
MAX16997/MAX16998
4
4
SWT
5
5
GND
6
6
WDI
8
8
ENABLE
—
2
RESETIN
—
3
SRT
—
7
RESET
_______________________________________________________________________________________
5
