Microprocessor
Supervisory Circuits
Data Sheet
ADM8690/ADM8691/ADM8695
FEATURES FUNCTIONAL BLOCK DIAGRAMS
Upgrade for the ADM690, ADM691, ADM695 and
V
BATT
for the MAX690, MAX691, MAX695
V
OUT
Specified over temperature
Low power consumption: 0.7 mW
V
CC
Precision voltage monitor
RESET
Reset assertion down to 1 V V
CC 1
RESET
4.65V
2
GENERATOR
Low switch on resistance: 0.7 normal, 7 in backup
High current drive: 100 mA
WATCHDOG
WATCHDOG
TRANSITION DETECTOR
Watchdog timer: 100 ms, 1.6 sec, or adjustable
INPUT (WDI)
(1.6sec) ADM8690
Standby current: 400 nA
POWER-FAIL
Automatic battery backup power switching
INPUT (PFI)
POWER-FAIL
OUTPUT (PFO)
Extremely fast gating of chip enable signals (3 ns) 1.3V
Voltage monitor for power fail
1
VOLTAGE DETECTOR = 4.65V
Available in TSSOP package
2
RESET PULSE WIDTH = 50ms
Figure 1. ADM8690
APPLICATIONS
Microprocessor systems
BATT ON
Computers
ADM8691/
V
Controllers BATT
ADM8695
Intelligent instruments
V
OUT
Automotive systems
V
CC
PRODUCT HIGHLIGHTS
CE
IN
CE
OUT
The ADM8690 is available in 8-lead PDIP and SOIC packages
LOW LINE
1
and provides the following functions: 4.65V
RESET
1. Power-on reset output during power-up, power-down,
OSC IN RESET AND
RESET
and brownout conditions. The output remains RESET
WATCHDOG RESET
GENERATOR
OSC SEL
TIME BASE
operational with V as low as 1 V.
CC
2. Battery backup switching for CMOS RAM, CMOS micro-
WATCHDOG
WATCHDOG WATCHDOG WATCHDOG
processor, or other low power logic.
INPUT (WDI)
TRANSITION DETECTOR TIMER
OUTPUT (WDO)
3. Reset pulse if the optional watchdog timer is not toggled
POWER-FAIL
within a specified time. POWER-FAIL
INPUT (PFI)
OUTPUT (PFO)
1.3V
4. 1.3 V threshold detector for power-fail warning, low battery
detection, or to monitor a power supply other than 5 V.
1
VOLTAGE DETECTOR = 4.65V
The ADM8691 and ADM8695 are available in 16-lead PDIP
Figure 2. ADM8691/ADM8695
and small outline packages (including TSSOP) and provide
three additional functions:
1. Write protection of CMOS RAM or EEPROM.
2. Adjustable reset and watchdog timeout periods.
3. Separate watchdog timeout, backup battery switchover, and
low VCC status outputs.
Rev. C
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00093-002
00093-001ADM8690/ADM8691/ADM8695 Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1 Power-Fail Warning Comparator ............................................. 14
Applications ....................................................................................... 1 Applications Information .............................................................. 15
Product Highlights ........................................................................... 1 Increasing the Drive Current .................................................... 15
Functional Block Diagrams ............................................................. 1 Using a Rechargeable Battery for Backup ............................... 15
Revision History ............................................................................... 2 Adding Hysteresis to the Power-Fail Comparator ................. 15
General Description ......................................................................... 3 Monitoring the Status of the Battery ....................................... 15
Specif icat ions ..................................................................................... 4 Alternate Watchdog Input Drive Circuits ............................... 16
Absolute Maximum Ratings ............................................................ 6 Typical Applications ....................................................................... 17
ESD Caution .................................................................................. 6 ADM8690 Applications ............................................................. 17
Pin Configurations and Function Descriptions ........................... 7 ADM8691/ADM8695 Applications ......................................... 17
Typical Performance Characteristics ............................................. 9 RESET Output ............................................................................ 18
Circuit Information ........................................................................ 11
Power-Fail Detector ................................................................... 18
Battery Switchover Section ........................................................ 11
RAM Write Protection............................................................... 18
RESET
Power-Fail Output ......................................................... 11 Watchdog Timer ......................................................................... 18
RESET Outline Dimensions ....................................................................... 19
Watchdog Timer ............................................................ 12
Ordering Guide .......................................................................... 22
Watchdog Output (WDO) (ADM8691/ADM8695) ................. 13
CE Gating and RAM Write Protection
(ADM8691/ADM8695) ............................................................. 13
9/06Rev. 0 to Rev. A
REVISION HISTORY
Updated Format .................................................................. Universal
1 2/11Rev. B to Rev. C
Changes to Absolute Maximum Ratings ........................................ 6
Deleted ADM8692 and ADM8693 ............................. Throughout
Updated Ordering Guide .............................................................. 20
Changes to Table 4 ............................................................................ 7
RESET
Change to Power-Fail Output Section ............................ 11
2/97Revision 0: Initial Version
Changes to ADM8691/ADM8695 Applications Section .......... 17
Updated Outline Dimensions ....................................................... 19
Changes to Ordering Guide .......................................................... 22
6/11Rev. A to Rev. B
Deleted ADM8694 ......................................................... Throughout
Updated Figure 11, Figure 12, and Figure 13 ................................ 9
Updated Outline Dimensions ....................................................... 18
Rev. C | Page 2 of 24