AD ADM698 Microprocessor supervisory circuit Datasheet

a
Microprocessor
Supervisory Circuits
ADM698/ADM699
FEATURES
Superior Upgrade for MAX698/MAX699
Guaranteed RESET Assertion with VCC = 1 V
Low 0.6 mA Supply Current
Precision 4.65 V Voltage Monitor
Power OK/Reset Time Delay
Watchdog Timer
Minimum Component Count
Performance Specified over Temperature
APPLICATIONS
Microprocessor Systems
Computers
Controllers
Intelligent Instruments
Automotive Systems
Critical mP Power Monitoring
FUNCTIONAL BLOCK DIAGRAM
ADM698/
ADM699
RESET*
VCC
RESET
GENERATOR
RESET
4.65V
WATCHDOG
INPUT
WDI*
WATCHDOG
TRANSITION DETECTOR
(1 sec)
WATCHDOG
OUTPUT WDO*
*WDI (ADM699 ONLY)
RESET (SOIC ONLY)
WDO (ADM699 SOIC ONLY)
TYPICAL APPLICATION CIRCUIT
GENERAL DESCRIPTION
The ADM698/ADM699 supervisory circuits provide power
supply monitoring and watchdog timing for microprocessor
systems.
The ADM698 monitors the 5 V VCC power supply and generates a RESET pulse during power up, power down and during
low voltage “Brown Out” conditions. The RESET output is
guaranteed to be functional (logic low) with VCC as low as 1 V.
The ADM699 features an identical monitoring circuit as in the
ADM698 plus an additional watchdog timer input to monitor
microprocessor activity. The RESET output is forced low if the
watchdog input is not toggled within the 1 second watchdog
timeout period.
+5V
VCC
µP POWER
RESET
µP RESET
ADM698/
ADM699
µP SYSTEM
WDI*
I/O LINE
GND
*ADM699 ONLY
Both parts are available in 8-pin plastic DIP and 16-lead SOIC
packages. The 16-lead SOIC contains additional outputs
RESET (without inversion) and Watchdog Output WDO
(ADM699 only).
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Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
ADM698/ADM699–SPECIFICATIONS (V
CC
= +5 V 6 10%, TA = TMIN to TMAX unless otherwise noted)
Parameter
Min
VCC Operating Voltage Range
Supply Current
3.0
Power-Down Reset Assertion
Power-Up Reset Deassertion
Reset Threshold Hysteresis
Reset Active Time
4.5
4.65
140
40
200
280
Watchdog Timeout Period (ADM699)
Minimum WDI Input Pulse Width
1.0
50
1.6
4
RESET Output Voltage
RESET Output Voltage (VCC = 1 V)
Typ
Max
Units
0.6
5.5
1.95
V
mA
4.73
4.73
V
V
mV
ms
TA = +25°C, VCC = +5 V
2.25
s
ns
TA = +25°C, VCC = +5 V
VIL = 0.4, VIH = 3.5 V
0.4
200
V
mV
V
V
V
mA
ISINK = 1.6 mA, Vcc = 4.4 V
ISINK = 10 µA, VCC = 1.0 V
ISOURCE = 1 µA, VCC = 5 V
ISINK = 1.6 mA, VCC = 5 V
ISOURCE = 1 µA, VCC = 4.4 V
Output Sink Current
V
V
µA
µA
WDI = VCC, TA = +25°C
WDI = 0 V, TA = +25°C
3.5
RESET and WDO Output Voltage
0.4
3.5
RESET Output Short Circuit Current
WDI Input Threshold (ADM699)
Logic Low
Logic High
WDI Input Current
25
0.8
3.5
–50
20
–20
50
Test Conditions/Comments
Specifications subject to change without notice.
ORDERING GUIDE
ABSOLUTE MAXIMUM RATINGS*
(TA = +25°C unless otherwise noted)
VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +6 V
All Other Inputs . . . . . . . . . . . . . . . . . . . –0.3 V to VCC + 0.3 V
Power Dissipation 8-Pin DIP . . . . . . . . . . . . . . . . . . . . 500 mW
θJA, Thermal Impedance . . . . . . . . . . . . . . . . . . . . +120°C/W
Power Dissipation 16-Pin SOIC . . . . . . . . . . . . . . . . . 375 mW
θJA, Thermal Impedance . . . . . . . . . . . . . . . . . . . . +110°C/W
Power Dissipation 8-Pin Cerdip . . . . . . . . . . . . . . . . . . 500 mW
θJA, Thermal Impedance . . . . . . . . . . . . . . . . . . . . +125°C/W
Operating Temperature Range
Industrial (A Version) . . . . . . . . . . . . . . . . . –40°C to +85°C
Extended (S Version) . . . . . . . . . . . . . . . . . –55°C to +125°C
Storage Temperature Range . . . . . . . . . . . . . –65°C to +150°C
Lead Temperature (Soldering, 10 secs) . . . . . . . . . . . . +300°C
Vapor Phase (60 secs) . . . . . . . . . . . . . . . . . . . . . . . +215°C
Infrared (15 secs) . . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C
Model
Temperature
Range
Package
Option
ADM698AN
ADM698AR
ADM698AQ
ADM698SQ
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–55°C to +125°C
N-8
R-16
Q-8
Q-8
ADM699AN
ADM699AR
ADM699AQ
ADM699SQ
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–55°C to +125°C
N-8
R-16
Q-8
Q-8
*Stresses above those listed under “Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of
the device at these or any other conditions above those listed in the operational
sections of this specification is not implied. Exposure to absolute maximum ratings
for extended periods of time may affect device reliability.
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the ADM698/ADM699 features proprietary ESD protection circuitry, permanent
damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper
ESD precautions are recommended to avoid performance degradation or loss of functionality.
–2–
WARNING!
ESD SENSITIVE DEVICE
REV. 0
ADM698/ADM699
PIN CONFIGURATION (DIP)
PIN FUNCTION DESCRIPTION
Mnemonic
VCC
GND
RESET
WDI
RESET
WDO
Function
+5 V Power Supply Input.
0 V. Ground reference for all signals.
Logic Output. RESET goes low whenever VCC
falls below the reset voltage threshold (4.65 V
typ). RESET remains low for a minimum of
140 ms after VCC returns to 5 V. RESET also
goes low for a minimum of 140 ms if the watchdog
timer is enabled but not serviced within its timeout period.
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 timer resets with each
transition on the WDI line. The watchdog timer
may be disabled if WDI is left floating or is driven
to midsupply.
(SOIC packages only) Logic Output. RESET is
an active high output. It is the inverse of RESET.
(SOIC ADM699 only) Logic Output. 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 midsupply, the watchdog timer is disabled and
WDO remains high.
1
VCC
2
GND
3
GND
4
ADM698/
ADM699
O
TOP VIEW
(Not to Scale)
8
GND
7
RESET
6
NC (WDI)*
5
NC
*( ) ADM699 ONLY
PIN CONFIGURATION (SOIC)
16 RESET
GND 1
VCC 2
VCC 3
O
ADM698/
TOP VIEW
ADM699
(Not to Scale)
15 RESET
14 NC (WDO)*
13 NC
TOP VIEW
NC 5 (Not to Scale) 12 NC
GND 4
NC 6
11 NC (WDI)*
NC 7
10 NC
NC 8
9 GND
*( ) ADM699 ONLY
215
TYPICAL PERFORMANCE CURVES
VCC = +5V
RESET ACTIVE TIME – ms
A4
VCC
3.36 V
100
90
AAAAAA
AAA
AAAAA
AAAA
210
205
200
10
0%
1V
1V
195
500ms
40
20
Figure 1. RESET Output Voltage vs. VCC
RESET VOLTAGE THRESHOLD – V
VCC = +5V
4.68
POWER UP
4.66
4.64
POWER DOWN
4.62
40
60
80
TEMPERATURE – °C
100
120
Figure 3. RESET Voltage Threshold vs. Temperature
REV. 0
80
100
120
Figure 2. RESET Active Time vs. Temperature
4.70
20
60
TEMPERATURE – °C
–3–
ADM698/ADM699
CIRCUIT INFORMATION
Power Fail RESET
The watchdog timer input (WDI) monitors an I/O line from the
µP system. The µP must toggle this input once every 1.6 seconds to verify correct software execution. Failure to toggle the
line indicates that the µP system is not correctly executing its
program and may be tied up in an endless loop. If this happens,
a reset pulse is generated to initialize the processor.
A precision voltage detector monitors VCC and generates a
RESET output to hold the microprocessor’s Reset line low when
VCC falls below the reset threshold (4.65 V) (see Figure 4). The
reset voltage threshold is set to accommodate a 5% variation on
VCC. The voltage detector has 40 mV hysteresis to ensure that
glitches on VCC do not activate the RESET output.
The WDI input is a three level input and will recognize a low
to- high or a high-to-low transition on its input. The watchdog
timer is reset by each WDI transition and then begins its
timeout period. If the WDI pin remains either high or low, reset
pulses will be issued every 1.6 seconds typically. If the watchdog timer is not needed, the WDI input should be left floating.
On power up, an internal monostable holds RESET low for
140 ms after VCC rises above the reset threshold. This allows the
power supply to stabilize on power up and also prevents repeated toggling of RESET even if the 5 V power drops out and
recovers with each power line cycle. In order to prevent
mistriggering due to transient voltage spikes, it is recommended
that a 0.1 µF capacitor be connected at the VCC pin.
The Watchdog Output (WDO) (SOIC package Only) provides
watchdog status information. It is driven low if WDI is not
toggled within the watchdog timeout period. It goes high at the
next WDI transition. It is also set high when VCC falls below the
reset threshold.
The RESET output is guaranteed to remain low with VCC as
low as 1 V. This holds the microprocessor in a stable shutdown
condition as the power supply comes up.
On the 16-lead SOIC package, an active high RESET output is
also provided. This is the complement of RESET and is intended for microprocessors requiring an active high signal.
V2
V1
V2
WDI
V1
WDO
t2
RESET
t1
t1
t2
RESET
t1
V1 = RESET VOLTAGE THRESHOLD
V2 = RESET VOLTAGE THRESHOLD +
THRESHOLD HYSTERESIS
t1 = RESET TIME
t1
t1
t1 = RESET TIME
t2 = WATCHDOG TIME OUT PERIOD
Figure 4. Watchdog Timeout Period vs. Temperature
Figure 5. Watchdog Timeout Period and Reset Active Time
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Pin Plastic DIP
(N-8)
8-Pin Cerdip
(Q-8)
5
8
0.310 (7.87)
0.220 (5.59)
PIN 1
1
4
0.420 (10.67)
MAX
0.200
(5.08)
MAX
16
9
0.419
(10.65)
0.299
(7.60)
0.060 (1.52)
0.015 (0.38)
1
0.150
(3.81)
MIN
SEATING
PLANE
0.022 (0.558)
0.014 (0.356)
16-Lead SOIC
(R-16)
8
0.413 (10.50)
0.012
(0.3)
0.100 (2.54)
BSC
0.320 (8.13)
0.290 (7.37)
0.015 (0.381)
0.008 (0.204)
–4–
PRINTED IN U.S.A.
VCC
C1784–18–4/93
Watchdog Timer (ADM699 Only)
0.070 (1.78)
0.30 (0.76)
0.104
(2.65)
0.05 (1.27)
REF
0.019 (0.49)
0.030
(0.75)
0.013
(0.32)
0.042
(1.07)
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