LTC692/LTC693
Microprocessor
Supervisory Circuits
FEATURES
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DESCRIPTION
The LTC
®
692/LTC693 provide complete power supply
monitoring and battery control functions for microproces-
sor reset, battery backup, 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 LTC692/LTC693 power 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
LTC692/LTC693 provide 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 Maximum) Onboard Gating of RAM Chip
Enable Signals
4.40V Precision Voltage Monitor
Power OK/Reset Time Delay: 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
SO8 and SO16 Packaging
APPLICATIONS
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Critical μP Power Monitoring
Intelligent Instruments
Battery-Powered Computers and Controllers
Automotive Systems
TYPICAL APPLICATION
5
V
IN
≥ 7.5V
LT1086-5
V
IN
ADJ
V
OUT
5V
RESET
Output Voltage vs
Supply Voltage
T
A
= 25°C
EXTERNAL PULL-UP = 10μA
V
BATT
= 0V
+
10μF
+
100μF
V
CC
0.1μF
LTC692
LTC693
V
BATT
3V
V
OUT
0.1μF
POWER TO
μP
CMOS RAM POWER
μP
SYSTEM
μP
RESET
μP NMI
I/O LINE
692_3 • TA01
RESET
OUTPUT VOLTAGE (V)
4
3
51k
PFI
10k
MICROPROCESSOR RESET, BATTERY BACKUP, POWER FAILURE
WARNING AND WATCHDOG TIMING ARE ALL IN A SINGLE CHIP
FOR MICROPROCESSOR SYSTEMS
GND
RESET
PFO
WDI
0.1μF
2
1
100Ω
0
0
1
3
4
2
SUPPLY VOLTAGE (V)
692_3 • TA02
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LTC692/LTC693
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 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
LTC692C/LTC693C ................................. 0°C to 70°C
LTC692I .............................................. –40°C to 85°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec) ................ 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
V
OUT
1
V
CC
2
GND 3
PFI 4
N8 PACKAGE
8-LEAD PDIP
8
7
6
5
V
BATT
RESET
WDI
PFO
V
BATT
V
OUT
V
CC
GND
BATT ON
LOW LINE
OSC IN
OSC SEL
1
2
3
4
5
6
7
8
16 RESET
15
RESET
14
WDO
13
CE
IN
12
CE
OUT
11 WDI
10
PFO
9
PFI
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 110°C,
θ
JA
= 130°C/W (N)
T
JMAX
= 110°C,
θ
JA
= 180°C/W (S)
S8 PACKAGE CONDITIONS: PCB MOUNT ON FR4 MATERIAL,
STILL AIR AT 25°C, COPPER TRACE
N PACKAGE
16-LEAD PDIP
SW PACKAGE
16-LEAD PLASTIC SO
T
JMAX
= 110°C,
θ
JA
= 130°C/W
S16 PACKAGE CONDITIONS: PCB MOUNT ON FR4 MATERIAL,
STILL AIR AT 25°C, COPPER TRACE
ORDER INFORMATION
LEAD FREE FINISH
LTC692CN8#PBF
LTC692CS8#PBF
LTC692IS8#PBF
LTC693CN#PBF
LTC693CS#PBF
TAPE AND REEL
LTC692CN8#TRPBF
LTC692CS8#TRPBF
LTC692IS8#TRPBF
LTC693CN#TRPBF
LTC693CS#TRPBF
PART MARKING
LTC692CN8
692
692I
LTC693CN
LTC693CS
PACKAGE DESCRIPTION
8-Lead Plastic DIP
8-Lead Plastic SO
8-Lead Plastic SO
16-Lead Plastic DIP
16-Lead Plastic SO
TEMPERATURE RANGE
0°C to 70°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
0°C to 70°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/
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LTC692/LTC693
PRODUCT SELECTION GUIDE
PINS
LTC692
LTC693
LTC690
LTC691
LTC694
LTC695
LTC699
LTC1232
LTC1235
LTC694-3.3
LTC695-3.3
8
16
8
16
8
16
8
8
16
8
16
RESET
THRESHOLD
(V)
4.40
4.40
4.65
4.65
4.65
4.65
4.65
4.37/4.62
4.65
2.90
2.90
WATCHDOG
TIMER
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
BATTERY
BACKUP
X
X
X
X
X
X
POWER-FAIL
WARNING
X
X
X
X
X
X
X
X
X
RAM WRITE-
PROTECT
PUSHBUTTON
RESET
CONDITIONAL
BATTERY
BACKUP
ELECTRICAL CHARACTERISTICS
PARAMETER
Battery Backup Switching
Operating Voltage Range
V
CC
V
BATT
V
OUT
Output Voltage
I
OUT
= 1mA
I
OUT
= 50mA
V
OUT
in Battery Backup Mode
Supply Current (Exclude I
OUT
)
Supply Current in Battery Backup 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
(Note 5)
I
SINK
= 3.2mA
CONDITIONS
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= full operating range, V
BATT
= 2.8V, unless otherwise noted.
MIN
TYP
MAX
UNITS
4.50
2.00
l
5.50
4.00
V
CC
– 0.005
V
CC
– 0.005
V
CC
– 0.250
V
BATT
– 0.02
0.6
0.6
0.04
0.04
1.5
2.5
1
5
0.02
0.10
70
50
20
0.4
V
V
V
V
V
V
mA
mA
μA
μA
μA
μA
mV
mV
mV
V
mA
μA
V
mV
ms
ms
V
CC
– 0.05
V
CC
– 0.10
V
CC
– 0.50
V
BATT
– 0.1
I
OUT
= 250μA, V
CC
< V
BATT
I
OUT
≤ 50mA
V
CC
= 0V, V
BATT
= 2.8V
5.5V > V
CC
> V
BATT
+ 0.2V
Power Up
Power Down
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l
–0.1
–1.0
BATT ON = V
OUT
, Sink Current
BATT ON = 0V, Source Current
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0.5
4.25
160
140
35
1
4.40
40
200
200
25
4.50
240
280
OSC SEL High, V
CC
= 5V
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LTC692/LTC693
ELECTRICAL CHARACTERISTICS
PARAMETER
Watchdog Timeout Period, Internal Oscillator
CONDITIONS
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)
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
= 3mA
I
SOURCE
= 1μA, VCC = 0V
V
CC
= 5V, C
L
= 20pF
Output Source Current
Output Sink Current
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The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= full operating range, V
BATT
= 2.8V, unless otherwise noted.
MIN
1.2
1.0
80
70
4032
960
1
1
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
Output Source Current
Output Sink Current
Logic Low
Logic High
WDI = V
OUT
WDI = 0V
V
CC
= 5V
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l
l
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TYP
1.6
1.6
100
100
MAX
2.00
2.25
120
140
4097
1025
UNITS
sec
sec
ms
ms
Clock
Cycles
ms/V
ms/V
ns
Long Period
Short Period
200
4
3.5
0.4
3.5
1
3
25
25
0.8
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
2.0
3
0.4
V
OUT
– 1.50
V
OUT
– 0.05
20
20
30
35
35
45
25
50
200
0.4
mV
V
V
V
V
μA
mA
V
V
μA
μA
V
mV/V
nA
V
V
μA
mA
μs
μs
μs
V
V
μA
V
V
V
ns
ns
mA
mA
1.35
I
SINK
= 3.2mA
I
SOURCE
= 1μA
PFI = High,
PFO
= 0V
PFI = Low,
PFO
= VOUT
ΔV
IN
= –20mV, V
OD
= 15mV
ΔV
IN
= 20mV, V
OD
= 15mV with 10kΩ
Pull-Up
V
IL
V
IH
CE
Propagation Delay
CE
OUT Output Short-Circuit Current
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LTC692/LTC693
ELECTRICAL CHARACTERISTICS
PARAMETER
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
OSC SEL = 0V
OSC SEL = 0V, C
OSC
= 47pF
l
The
l
denotes the specifications which apply over the full 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
TYP
±2
5
0
4
250
MAX
UNITS
μA
μA
kHz
kHz
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, 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 LTC692/LTC693 have minimum reset active times of 140ms
(200ms typically). The reset active time of the LTC693 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
pull-ups which pull to the supply when the input pins are floating.
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Analog electronics
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