LTC690/LTC691
LTC694/LTC695
Microprocessor
Supervisory Circuits
FEATURES
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DESCRIPTION
The LTC
®
690 family provides complete power supply
monitoring and battery control functions for microprocessor
reset, battery back-up, CMOS RAM write protection, power
failure warning and watchdog timing. A precise internal
voltage reference and comparator circuit monitor the power
supply line. When an out-of-tolerance condition occurs,
the reset outputs are forced to active states and the chip
enable output unconditionally write-protects external
memory. In addition, the
RESET
output is guaranteed to
remain logic low even with V
CC
as low as 1V.
The LTC690 family powers the active CMOS RAMs with a
charge pumped NMOS power switch to achieve low drop-
out and low supply current. When primary power is lost,
auxiliary power, connected to the battery input pin, powers
the RAMs in standby through an efficient PMOS switch.
For an early warning of impending power failure, the LTC690
family provides an internal comparator with a user-defined
threshold. An internal watchdog timer is also available, which
forces the reset pins to active states when the watchdog
input is not toggled prior to a preset timeout period.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Guaranteed
Reset Assertion at V
CC
= 1V
1.5mA Maximum Supply Current
Fast (35ns Max) Onboard Gating of RAM Chip
Enable Signals
SO-8 and S16 Packaging
4.65V Precision Voltage Monitor
Power OK/Reset Time Delay: 50ms, 200ms
or Adjustable
Minimum External Component Count
1µA Maximum Standby Current
Voltage Monitor for Power-Fail
or Low-Battery Warning
Thermal Limiting
Performance Specified Over Temperature
Superior Upgrade for MAX690 Family
APPLICATIONS
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Critical μP Power Monitoring
Intelligent Instruments
Battery-Powered Computers and Controllers
Automotive Systems
TYPICAL APPLICATION
RESET
Output Voltage
vs Supply Voltage
5
V
IN
≥ 7.5V
LT 1086-5
V
IN
10μF
ADJ
V
OUT
®
5V
+
+
100μF
V
OUT
0.1μF
LTC690/LTC691
LTC694/LTC695
V
BATT
RESET
PFO
PFI
GND
WDI
μP
SYSTEM
μP
RESET
μP NMI
I/O LINE
690 TA01
RESET
OUTPUT VOLTAGE (V)
V
CC
POWER TO
μP
CMOS RAM POWER
0.1μF
4
3
T
A
= 25°C
EXTERNAL PULL-UP = 10μA
V
BATT
= 0V
3V
51k
2
1
10k
MICROPROCESSOR RESET, BATTERY BACK-UP, POWER FAILURE
WARNING AND WATCHDOG TIMING ARE ALL IN A SINGLE CHIP
FOR MICROPROCESSOR SYSTEMS
0.1μF
100Ω
0
0
1
3
4
2
SUPPLY VOLTAGE (V)
5
690 TA02
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LTC690/LTC691
LTC694/LTC695
ABSOLUTE MAXIMUM RATINGS
(Notes 1 and 2)
Terminal Voltage
V
CC
..................................................... – 0.3V to 6.0V
V
BATT
.................................................. –0.3V to 6.0V
All Other Inputs ....................– 0.3V to (V
OUT
+ 0.3V)
Input Current
V
CC
................................................................200mA
V
BATT
...............................................................50mA
GND.................................................................20mA
V
OUT
Output Current ...................Short-Circuit Protected
Power Dissipation ...............................................500mW
Operating Temperature Range
LTC690/91/94/95C ............................... 0°C to 70°C
LTC690/91/94/95I ............................– 40°C to 85°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec.) ................. 300°C
PIN CONFIGURATION
TOP VIEW
V
BATT
V
OUT
V
CC
GND
BATT ON
LOW⎯
LINE
OSC IN
OSC SEL
1
2
3
4
5
6
7
8
N PACKAGE
16-LEAD PDIP
T
JMAX
= 110°C,
θ
JA
= 130°C/W
TOP VIEW
V
OUT
V
CC
GND
1
2
3
8
7
6
5
N8 PACKAGE
8-LEAD PDIP
T
JMAX
= 110°C,
θ
JA
= 130°C/W (N8)
V
BATT
RESET
WDI
PFO
V
OUT
V
CC
GND
PFI
1
2
3
4
16 RESET
15
RESET
14
WDO
13
CE
IN
12
CE
OUT
V
BATT
1
V
OUT
2
V
CC
3
GND 4
BATT ON 5
LOW⎯
LINE
6
OSC IN 7
OSC SEL 8
TOP VIEW
16 RESET
15
RESET
14
WDO
13
CE
IN
12
CE
OUT
11 WDI
10
PFO
9 PFI
11 WDI
10
PFO
9
PFI
SW PACKAGE
16-LEAD WIDE PLASTIC SO
T
JMAX
= 110°C,
θ
JA
= 130°C/W CONDITIONS: PCB MOUNT ON
FR4 MATERIAL, STILL AIR AT 25°C, COPPER TRACE
TOP VIEW
8
7
6
5
VBATT
RESET
WDI
PFO
PFI 4
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 110°C,
θ
JA
= 180°C/W CONDITIONS; PCB MOUNT ON
FR4 MATERIAL, STILL AIR AT 25°C, COPPER TRACE
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LTC690/LTC691
LTC694/LTC695
ORDER INFORMATION
LEAD FREE FINISH
LTC691CN#PBF
LTC691IN#PBF
LTC695CN#PBF
LTC695IN#PBF
LTC691CSW#PBF
LTC691ISW#PBF
LTC695CSW#PBF
LTC695ISW#PBF
LTC690CN8#PBF
LTC690IN8#PBF
LTC694CN8#PBF
LTC694IN8#PBF
LTC690CS8#PBF
LTC690IS8#PBF
LTC694CS8#PBF
LTC694IS8#PBF
TAPE AND REEL
LTC691CN#PBF
LTC691IN#PBF
LTC695CN#PBF
LTC695IN#PBF
LTC691CSW#PBF
LTC691ISW#PBF
LTC695CSW#PBF
LTC695ISW#PBF
LTC690CN8#PBF
LTC690IN8#PBF
LTC694CN8#PBF
LTC694IN8#PBF
LTC690CS8#PBF
LTC690IS8#PBF
LTC694CS8#PBF
LTC694IS8#PBF
PART MARKING
LTC691CN
LTC691IN
LTC695CN
LTC695IN
LTC691CSW
LTC691ISW
LTC695CSW
LTC695ISW
LTC690CN8
LTC690IN8
LTC694CN8
LTC694IN8
LTC690CS8
LTC690IS8
LTC694CS8
LTC694IS8
PACKAGE DESCRIPTION
16-Lead PDIP
16-Lead PDIP
16-Lead PDIP
16-Lead PDIP
16-Lead Wide Plastic SO
16-Lead Wide Plastic SO
16-Lead Wide Plastic SO
16-Lead Wide Plastic SO
8-Lead PDIP
8-Lead PDIP
8-Lead PDIP
8-Lead PDIP
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
PRODUCT SELECTION GUIDE
PINS
LTC690
LTC691
LTC694
LTC695
LTC699
LTC1232
LTC1235
8
16
8
16
8
8
16
RESET
X
X
X
X
X
X
X
WATCHDOG
TIMER
X
X
X
X
X
X
X
X
X
X
X
X
X
BATTERY
BACK-UP
X
X
X
X
POWER-FAIL
WARNING
X
X
X
X
X
X
RAM WRITE
PROTECT
PUSHBUTTON
RESET
CONDITIONAL
BATTERY
BACK-UP
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LTC690/LTC691
LTC694/LTC695
ELECTRICAL CHARACTERISTICS
PARAMETER
Battery Back-Up Switching
Operating Voltage Range
V
OUT
Output Voltage
V
CC
V
BATT
I
OUT
= 1mA
I
OUT
= 50mA
V
OUT
in Battery Back-Up Mode
Supply Current (Exclude I
OUT
)
Supply Current in Battery Back-Up Mode
Battery Standby Current (+ = Discharge, – = Charge)
Battery Switchover Threshold, V
CC
– V
BATT
Battery Switchover Hysteresis
BATT ON Output Voltage (Note 4)
BATT ON Output Short-Circuit Current (Note 4)
Reset and Watchdog Timer
Reset Voltage Threshold
Reset Threshold Hysteresis
Reset Active Time (LTC690/91) (Note 5)
Reset Active Time (LTC694/95) (Note 5)
Watchdog Timeout Period, Internal Oscillator
OSC SEL HIGH, V
CC
= 5V
OSC SEL HIGH, V
CC
= 5V
Long Period, V
CC
= 5V
Short Period, V
CC
= 5V
Watchdog Timeout Period, External Clock (Note 6)
Reset Active Time PSRR
Watchdog Timeout Period PSRR, Internal OSC
Minimum WDI Input Pulse Width
RESET
Output Voltage at V
CC
= 1V
RESET
and
LOW⎯LINE
Output Voltage (Note 4)
RESET
and
WDO
Output Voltage (Note 4)
V
IL
= 0.4V, V
IH
= 3.5V
I
SINK
= 10μA, V
CC
= 1V
I
SINK
= 1.6mA, V
CC
= 4.25V
I
SOURCE
= 1μA, V
CC
= 5V
I
SINK
= 1.6mA, V
CC
= 5V
I
SOURCE
= 1μA, V
CC
= 4.25V
3.5
0.4
3.5
l
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l
The
l
denotes specifications which apply over the operating temperature
range, otherwise specifications are at T
A
= 25°C. V
CC
= full operating range, V
BATT
= 2.8V, unless otherwise noted.
CONDITIONS
MIN
4.75
2.00
V
CC
– 0.05 V
CC
– 0.005
V
CC
– 0.10 V
CC
– 0.005
V
CC
– 0.50 V
CC
– 0.250
V
BATT
– 0.1 V
BATT
– 0.2
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TYP
MAX
5.50
4.25
UNITS
V
V
V
V
V
V
I
OUT
= 250μA, V
CC
< V
BATT
I
OUT
= 50mA
V
CC
= 0V, V
BATT
= 2.8V
5.5 > V
CC
> V
BATT
+ 0.2V
Power Up
Power Down
I
SINK
= 3.2mA
BATT ON = V
OUT
Sink Current
BATT ON = 0V Source Current
0.6
0.6
0.04
0.04
–0.1
–0.1
70
50
20
1.5
2.5
1
5
+0.02
+0.10
mA
mA
μA
μA
μA
μA
mV
mV
mV
0.4
35
0.5
4.5
40
35
160
140
1.2
1
80
70
4032
960
1
1
200
4
200
0.4
1
4.65
40
50
50
200
200
1.6
1.6
100
100
60
70
240
280
2.00
2.25
120
140
4097
1025
25
4.75
V
m
μA
V
mV
ms
ms
ms
ms
sec
sec
ms
ms
Clock
Cycles
ms/V
ms/V
ns
mV
V
V
V
V
Long Period
Short Period
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LTC690/LTC691
LTC694/LTC695
ELECTRICAL CHARACTERISTICS
PARAMETER
RESET,
RESET, WDO, LOW⎯
LINE
Output Short-Circuit Current (Note 4)
WDI Input Threshold
WDI Input Current
Power-Fail Detector
PFI Input Threshold
PFI Input Threshold PSRR
PFI Input Current
PFO
Output Voltage (Note 4)
PFO
Short-Circuit Source Current (Note 4)
PFI Comparator Response Time (Falling)
PFI Comparator Response Time (Rising) (Note 4)
Chip Enable Gating
CE
IN Threshold
CE
IN Pull-Up Current (Note 7)
CE
OUT Output Voltage
I
SINK
= 3.2mA
I
SOURCE
= 3.0mA
I
SOURCE
= 1μA, V
CC
= 0V
V
CC
= 5V, C
L
= 20pF
Output Source Current
Output Sink Current
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The
l
denotes specifications which apply over the operating temperature
range, otherwise specifications are at T
A
= 25°C. V
CC
= full operating range, V
BATT
= 2.8V, unless otherwise noted.
CONDITIONS
Output Source Current
Output Sink Current
Logic Low
Logic high
WDI = V
OUT
WDI = 0V
V
CC
= 5V
l
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MIN
1
TYP
3
25
MAX
25
0.8
UNITS
μA
mA
V
μA
3.5
–50
1.25
4
–8
1.3
0.3
±0.01
±25
0.4
3.5
1
3
25
2
40
8
0.8
2
3
0.4
V
OUT
– 1.50
V
OUT
– 0.05
20
20
30
35
±2
5
35
45
ns
mA
μA
V
25
μA
mA
μs
μs
50
1.35
V
mV/V
nA
V
I
SINK
= 3.2mA
I
SOURCE
= 1μA
PFI = HIGH,
PFO
= 0V
PFI = LOW,
PFO
= V
OUT
ΔV
IN
= –20mV, V
OD
= 15mV
ΔV
IN
= 20mV, V
OD
= 15mV
with 10kΩ Pull-Up
V
IL
V
IH
V
CE
Propagation Delay
CE
OUT Output Short-Circuit Current
Oscillator
OSC IN Input Current (Note 7)
OSC SEL Input Pull-Up Current (Note 7)
OSC IN Frequency Range
OSC IN Frequency with External Capacitor
μA
μA
250
kHz
kHz
OSC SEL = 0V
OSC SEL = 0V, C
OSC
= 47pF
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4
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
All voltage values are with respect to GND.
Note 3:
For military temperature range parts or for the LTC692 and
LTC693, consult the factory.
Note 4:
The output pins of BATT ON,
LOW⎯LINE, PFO, WDO, RESET
and
RESET have weak internal pull-ups of typically 3μA. However, external pull-
up resistors may be used when higher speed is required.
Note 5:
The LTC690 and LTC691 have minimum reset active time of 35ms
(50ms typically) while the LTC694 and LTC695 have longer minimum
reset active time of 140ms (200ms typically). The reset active time of
the LTC691 and LTC695 can be adjusted (see Table 2 in Applications
Information section).
Note 6:
The external clock feeding into the circuit passes through the
oscillator before clocking the watchdog timer (See Block Diagram).
Variation in the timeout period is caused by phase errors which occur
when the oscillator divides the external clock by 64. The resulting variation
in the timeout period is 64 clocks plus one clock of jitter.
Note 7:
The input pins of
CE
IN, OSC IN and OSC SEL have weak internal
pullups which pull to the supply when the input pins are floating.
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