Low Voltage Supervisory Circuits with
Watchdog Timer in 4-Lead SC70
ADM8616/ADM8617
Data Sheet
FEATURES
FUNCTIONAL BLOCK DIAGRAM
ADM8616
VCC
VCC
RESET
GENERATOR
VREF
RESET
WATCHDOG
DETECTOR
GND
WDI
04795-001
Precision 1.8 V to 5 V power supply monitoring
9 RESET threshold options
1.58 V to 4.63 V
4 RESET timeout options
1 ms, 20 ms, 140 ms, 1120 ms
3 watchdog timeout options
6.3 ms, 102 ms, 1.6 sec
RESET output stages
Push-pull active-low (ADM8616)
Open-drain active-low (ADM8617)
Low power consumption (5 μA)
Guaranteed reset output valid to VCC = 1 V
Power supply glitch immunity
Specified over −40°C to +85°C temperature range
4-lead SC70 package
Figure 1.
APPLICATIONS
Microprocessor systems
Computers
Controllers
Intelligent instruments
Portable equipment
GENERAL DESCRIPTION
The ADM8616/ADM8617 are supervisory circuits that monitor
power supply voltage levels and code execution integrity in microprocessor-based systems. A power-on reset signal generates when
the supply voltage rises to a preset threshold level. The ADM8616/
ADM8617 have an on-chip watchdog timer that can reset the
microprocessor if it fails to strobe within a preset timeout
period.
The parts differ in terms of reset output configuration. The
ADM8616 is active-low with a push-pull output, while the
ADM8617 is active-low with an open-drain output.
The ADM8616/ADM8617 are available in 4-lead SC70 packages
and typically consume only 5 μA, making them suitable for use
in low power, portable applications.
Each part is available in the following nine reset threshold
options: 1.58 V, 1.67 V, 2.19 V, 2.32 V, 2.63 V, 2.93 V, 3.08 V,
4.38 V, and 4.63 V. There are four reset timeout options: 1 ms,
20 ms, 140 ms, and 1120 ms. There are also three possible
watchdog timeouts available: 6.3 ms, 102 ms, and 1.6 sec. Not
all device options are released for sale as standard models. See
the Ordering Guide for details.
Rev. C
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rights of third parties that may result from its use. Specifications subject to change without notice. No
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Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2005–2018 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
ADM8616/ADM8617
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Circuit Description............................................................................8
Applications ....................................................................................... 1
RESET Output ...............................................................................8
Functional Block Diagram .............................................................. 1
Watchdog Input .............................................................................8
General Description ......................................................................... 1
Application Information ...................................................................9
Revision History ............................................................................... 2
Watchdog Input Current ..............................................................9
Specifications..................................................................................... 3
Negative-Going VCC Transients ...................................................9
Absolute Maximum Ratings............................................................ 4
Ensuring RESET Valid to VCC = 0 V ...........................................9
ESD Caution .................................................................................. 4
Watchdog Software Considerations ............................................9
Pin Configuration and Function Descriptions ............................. 5
Outline Dimensions ....................................................................... 10
Typical Performance Characteristics ............................................. 6
Ordering Guide .......................................................................... 10
REVISION HISTORY
2/2018—Rev. B to Rev. C
Changes to General Description Section ...................................... 1
Added Note 1, Table 1 ...................................................................... 3
Moved Ordering Guide.................................................................. 10
Changes to Figure 16 and Ordering Guide ................................. 10
11/2006—Rev. 0 to Rev. A
Changes to Ordering Guide .......................................................... 10
6/2005—Revision 0: Initial Version
1/2007—Rev. A to Rev. B
Changes to Functional Block Diagram .......................................... 1
Rev. C | Page 2 of 10
Data Sheet
ADM8616/ADM8617
SPECIFICATIONS
VCC = full operating range, TA = −40oC to +85oC, unless otherwise noted.
Table 1.
Parameter
SUPPLY
VCC Operating Voltage Range
Supply Current
RESET THRESHOLD VOLTAGE 1
ADM861xL
ADM861xM
ADM861xT
ADM861xS
ADM861xR
ADM861xZ
ADM861xY
ADM861xW
ADM861xV
RESET THRESHOLD TEMPERATURE COEFFICIENT
Min
Max
Unit
Test Conditions/Comments
10
5
5.5
20
12
V
µA
µA
VCC = 5.5 V
VCC = 3.6 V
4.75
4.50
3.15
3.00
2.70
2.38
2.25
1.71
1.62
V
V
V
V
V
V
V
V
V
ppm/°C
1
4.50
4.25
3.00
2.85
2.55
2.25
2.12
1.62
1.52
4.63
4.38
3.08
2.93
2.63
2.32
2.19
1.67
1.58
40
2 × VTH
RESET THRESHOLD HYSTERESIS
RESET TIMEOUT PERIOD1
ADM861xxA
ADM861xxB
ADM861xxC
ADM861xxD
VCC TO RESET DELAY
Typ
1
20
140
1120
1.4
28
200
1600
40
RESET OUTPUT VOLTAGE
VOL (Open-Drain and Push-Pull)
VOH (Push-Pull Only)
0.8 × VCC
VCC − 1.5
4.3
71
1.12
50
5
25
1
6.3
102
1.6
9.3
153
2.4
ms
ms
ms
ms
µs
V
V
V
V
V
V
ns
µA
ms
ms
sec
ns
V
VCC falling at 1 mV/µs
VCC ≥ 1.0 V, ISINK = 50 µA
VCC ≥ 1.2 V, ISINK = 100 µA
VCC ≥ 2.7 V, ISINK = 1.2 mA
VCC ≥ 4.5 V, ISINK = 3.2 mA
VCC ≥ 2.7 V, ISOURCE = 500 µA
VCC ≥ 4.5 V, ISOURCE = 800 µA
From 10% to 90% VCC, CL = 5 pF, VCC = 3.3 V
VIL = 0.3 × VCC, VIH = 0.7 × VCC
0.3 × VCC
0.7 × VCC
−20
1
2
40
280
2240
0.3
0.3
0.3
0.4
RESET Rise Time
Open-Drain RESET Output Leakage Current
WATCHDOG INPUT
Watchdog Timeout Period1
ADM861xxxW
ADM861xxxX
ADM861xxxY
WDI Pulse Width
WDI Input Threshold
VIL
VIH
WDI Input Current
mV
120
−15
160
Not all device options are released for sale as standard models. See the Ordering Guide for details.
Rev. C | Page 3 of 10
V
µA
µA
VWDI = VCC
VWDI = 0
ADM8616/ADM8617
Data Sheet
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
Table 2.
Parameter
VCC
RESET
Output Current (RESET)
Operating Temperature Range
Storage Temperature Range
θJA Thermal Impedance, SC70
Soldering Temperature
Sn/Pb
Pb-Free
Rating
−0.3 V to +6 V
−0.3 V to +6 V
20 mA
−40°C to +85°C
−65°C to +150°C
146°C/W
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
ESD CAUTION
240°C, 30 sec
260°C, 40 sec
Rev. C | Page 4 of 10
Data Sheet
ADM8616/ADM8617
GND 1
RESET 2
ADM8616/
ADM8617
TOP VIEW
(Not to Scale)
4
VCC
3
WDI
04795-002
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
Figure 2. Pin Configuration
Table 3. Pin Function Descriptions
Pin No.
1
2
Mnemonic
GND
RESET
3
WDI
4
VCC
Description
Ground.
Active-Low RESET Output. Asserted whenever VCC is below the reset threshold (VTH).
Push-Pull Output Stage for ADM8616.
Open-Drain Output Stage for ADM8617.
Watchdog Input. Generates a RESET if the logic level on the pin remains low or high for the duration of the
watchdog timeout. The timer is cleared if a logic transition occurs on this pin, or if a reset is generated. Leave
floating to disable the watchdog timer.
Power Supply Voltage Being Monitored.
Rev. C | Page 5 of 10
ADM8616/ADM8617
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
1.20
10.0
9.5
8.5
NORMALIZED WATCHDOG TIMEOUT
9.0
VCC = 5V
8.0
ICC (µA)
7.5
7.0
6.5
VCC = 3.3V
6.0
5.5
5.0
4.5
VCC = 1.5V
1.15
1.10
1.05
1.00
0.95
–20
0
20
40
60
TEMPERATURE (°C)
80
100
120
0.90
–40
04795-003
Figure 3. Supply Current vs. Temperature
20
40
60
TEMPERATURE (°C)
80
100
120
1.05
1.04
NORMALIZED RESET THRESHOLD
1.15
NORMALIZED RESET TIMEOUT
0
Figure 6. Normalized Watchdog Timeout Period vs. Temperature
1.20
1.10
1.05
1.00
0.95
0.90
0.85
1.03
1.02
1.01
1.00
0.99
0.98
0.97
0.96
–20
0
20
40
60
TEMPERATURE (°C)
80
100
120
0.95
–40
04795-004
0.80
–40
–20
Figure 4. Normalized RESET Timeout Period vs. Temperature
–20
0
20
40
60
TEMPERATURE (°C)
80
100
120
04795-007
3.5
–40
04795-006
4.0
Figure 7. Normalized RESET Threshold vs. Temperature
100
160
90
140
60
50
40
30
20
100
80
60
40
20
10
0
–40
120
–20
0
20
40
60
TEMPERATURE (°C)
80
100
120
Figure 5. VCC to RESET Output Delay vs. Temperature
0
10
VCC = 2.93V
VCC = 4.63V
100
RESET THRESHOLD OVERDRIVE (mV)
1000
04795-008
MINIMUM PULSE WIDTH (µs)
70
04795-005
VCC TO RESET DELAY (µs)
80
Figure 8. Maximum VCC Transient Duration vs. RESET Threshold Overdrive
Rev. C | Page 6 of 10
Data Sheet
ADM8616/ADM8617
0.20
2.92
VCC = 2.9V
VCC = 2.9V
2.90
0.15
VOUT (V)
0.10
2.86
0.05
0
0
1
2
3
4
ISINK (mA)
5
6
7
2.82
0
Figure 9. Voltage Output Low vs. ISINK
0.2
0.4
0.6
ISOURCE (mA)
0.8
Figure 10. Voltage Output High vs. ISOURCE
Rev. C | Page 7 of 10
1.0
04795-010
2.84
04795-009
VOUT (V)
2.88
ADM8616/ADM8617
Data Sheet
CIRCUIT DESCRIPTION
RESET OUTPUT
The ADM8616 features an active-low, push-pull RESET output,
while the ADM8617 features an active-low, open-drain RESET
output. The RESET signal is guaranteed to be logic low and
logic high, respectively, for VCC down to 1 V.
The RESET output is asserted when VCC is below the RESET
threshold (VTH), or when WDI is not serviced within the
watchdog timeout period (tWD). RESET remains asserted for the
duration of the RESET active timeout period (tRP) after VCC rises
above the RESET threshold or after the watchdog timer times
out. Figure 11 illustrates the behavior of the RESET outputs.
VCC
VTH
The ADM8616/ADM8617 feature a watchdog timer that
monitors microprocessor activity. A timer circuit is cleared with
every low-to-high or high-to-low logic transition on the watchdog input pin (WDI), which detects pulses as short as 50 ns. If
the timer counts through the preset watchdog timeout period
(tWD), RESET is asserted. The microprocessor is required to
toggle the WDI pin to avoid being reset. Failure of the microprocessor to toggle WDI within the timeout period, therefore,
indicates a code execution error, and the RESET pulse generated
restarts the microprocessor in a known state.
In addition to logic transitions on WDI, the watchdog timer is
also cleared by a RESET assertion due to an undervoltage condition on VCC. When RESET is asserted, the watchdog timer is
cleared and does not begin counting again until RESET deasserts.
The watchdog timer can be disabled by leaving WDI floating or
by three-stating the WDI driver.
VCC
RESET
VTH
1V
0V
VCC
RESET
tRP
0V
tRD
04795-011
VCC
WATCHDOG INPUT
Figure 11. RESET Timing Diagram
Rev. C | Page 8 of 10
VCC
VTH
1V
0V
VCC
tRP
tWD
tRD
0V
WDI
VCC
04795-012
The ADM8616/ADM8617 provide microprocessor supply
voltage supervision by controlling the microprocessors RESET
input. Code execution errors are avoided during power-up,
power-down, and brownout conditions by asserting a RESET
signal when the supply voltage is below a preset threshold and
by allowing supply voltage stabilization with a fixed timeout
RESET after the supply voltage rises above the threshold. In
addition, problems with microprocessor code execution can be
monitored and corrected with a watchdog timer. By including
watchdog strobe instructions in microprocessor code, a watchdog timer can detect if the microprocessor code breaks down or
becomes stuck in an infinite loop. If this happens, the watchdog
timer asserts a RESET pulse that restarts the microprocessor in
a known state.
0V
Figure 12. Watchdog Timing Diagram
Data Sheet
ADM8616/ADM8617
APPLICATION INFORMATION
WATCHDOG INPUT CURRENT
WATCHDOG SOFTWARE CONSIDERATIONS
To minimize watchdog input current (and minimize overall
power consumption), leave WDI low for the majority of the
watchdog timeout period. When driven high, WDI can draw as
much as 160 µA. Pulsing WDI low-high-low at a low duty cycle
reduces the effect of the large input current. When WDI is
unconnected, a window comparator disconnects the watchdog
timer from the RESET output circuitry so that RESET is not
asserted when the watchdog timer times out.
In implementing the microprocessors watchdog strobe code,
quickly switching WDI low to high and then high to low (minimizing WDI high time) is desirable for current consumption
reasons. However, a more effective way of using the watchdog
function can be considered.
NEGATIVE-GOING VCC TRANSIENTS
To avoid unnecessary resets caused by fast power supply
transients, the ADM8616/ADM8617 are equipped with glitch
rejection circuitry. The typical performance characteristic in
Figure 8 plots VCC transient duration vs. transient magnitude.
The curve shows combinations of transient magnitude and
duration for which a RESET is not generated for 4.63 V and
2.93 V reset threshold parts. For example, with the 2.93 V
threshold, a transient that goes 100 mV below the threshold
and lasts 8 µs typically does not cause a RESET, but if the
transient is any bigger in magnitude or duration, a RESET is
generated. An optional 0.1 µF bypass capacitor mounted close
to VCC provides additional glitch rejection.
A low-high-low WDI pulse within a given subroutine prevents
the watchdog from timing out. However, if the subroutine
becomes stuck in an infinite loop, the watchdog does not detect
this because the subroutine continues to toggle WDI. A more
effective coding scheme for detecting this error involves using a
slightly longer watchdog timeout. In the program that calls the
subroutine, WDI is set high. The subroutine sets WDI low when
it is called. If the program executes without error, WDI is toggled
high and low with every loop of the program. If the subroutine
enters an infinite loop, WDI is kept low, the watchdog times
out, and the microprocessor is reset.
ENSURING RESET VALID TO VCC = 0 V
The active-low RESET output is guaranteed to be valid for
VCC as low as 1 V. However, by using an external resistor,
valid outputs for VCC as low as 0 V are possible. The resistor,
connected between RESET and ground, pulls the output low
when it is unable to sink current. A large resistance, such as
100 kΩ, must be used so that it does not overload the RESET
output when VCC is above 1 V.
START
SET WDI
HIGH
RESET
PROGRAM
CODE
INFINITE LOOP:
WATCHDOG
TIMES OUT
SUBROUTINE
04795-014
SET WDI
LOW
RETURN
Figure 14. Watchdog Flow Diagram
VCC
VCC
RESET
RESET
RESET
ADM8616/
ADM8617
100kΩ
WDI
µP
I/O
04795-015
04795-013
ADM8616/
ADM8617
Figure 13. Ensuring RESET Valid to VCC = 0 V
Figure 15. Typical Application Circuit
Rev. C | Page 9 of 10
ADM8616/ADM8617
Data Sheet
OUTLINE DIMENSIONS
2.20
1.80
0.65 0.65
BSC BSC
1.35
1.15
4
3
1
2.40
1.80
2
PIN 1
INDICATOR
0.50 BSC
0.40
0.10
1.10
0.80
0.10 MAX
COPLANARITY
0.10
*0.70
0.50
0.30
0.15
SEATING
PLANE
0.18
0.10
0.30
0.10
03-04-2014-B
1.00
0.80
*PACKAGE OUTLINE CORRESPONDS IN FULL TO EIAJ SC82
EXCEPT FOR WIDTH OF PIN 2 AS SHOWN.
Figure 16. 4-Lead Thin Shrink Small Outline Transistor Package [SC70]
(KS-4)
Dimensions shown in millimeters
ADM861 x x x x x KS x-RL7
GENERIC NUMBER
(6/7)
ORDERING QUANTITY
RL7: 3,000 PIECE REEL
Z: RoHS COMPLIANT
PACKAGE CODE
KS: 4-LEAD SC70
RESET TIMEOUT PERIOD
A: 1ms (MIN)
B: 20ms (MIN)
C: 140ms (MIN)
D: 1120ms (MIN)
TEMPERATURE RANGE
A: –40°C TO +85°C
WATCHDOG TIMEOUT PERIOD
W: 6.3ms (TYP)
X: 102ms (TYP)
Y: 1.6s (TYP)
04795-016
RESET THRESHOLD
L: 4.63V
M: 4.38V
T: 3.08V
S: 2.93V
R: 2.63V
Z: 2.32V
Y: 2.19V
W: 1.67V
V: 1.58V
Figure 17. Ordering Code Structure
ORDERING GUIDE
Model 1, 2, 3
ADM8616LCYAKSZ-RL7
ADM8616WCYAKSZ-RL7
ADM8617SAYAKSZ-RL7
ADM8617RCYAKSZ-RL7
Reset
Threshold (V)
4.63
1.67
2.93
2.63
Reset Timeout
Minimum (ms)
140
140
1
140
Watchdog
Timeout (sec)
1.6
1.6
1.6
1.6
Temperature
Range
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
Qty
3,000
3,000
3,000
3,000
Package
Description
4-Lead SC70
4-Lead SC70
4-Lead SC70
4-Lead SC70
Package
Option
KS-4
KS-4
KS-4
KS-4
Marking
Code
N0F
N0F
M4X
M4X
The ADM8616/ADM8617 include many device options; however, not all options are released for sale. Released options are called standard models and are listed in the
Ordering Guide. The Watchdog Timers page on the Analog Devices website also lists standard models. Contact a sales representative for information on nonstandard
models and be aware that samples and production units have very long lead times.
2
If ordering nonstandard models, complete the ordering code shown in Figure 17 by inserting reset threshold, reset timeout, and watchdog timeout suffixes.
3
Z = RoHS Compliant Part.
1
©2005–2018 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D04795-0-2/18(C)
Rev. C | Page 10 of 10
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