LTC692/LTC693
Microprocessor
Supervisory Circuits
FEATURES
s
s
s
s
DESCRIPTIO
®
s
s
s
s
s
s
s
s
s
UL Recognized
®
Guaranteed
Reset Assertion at V
CC
= 1V
1.5mA Maximum Supply Current
Fast (35ns Max.) On-Board Gating of RAM Chip
Enable Signals
SO8 and SO16 Packaging
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
The LTC692/LTC693 provide complete power supply moni-
toring and battery control functions for microprocessor
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 exter-
nal 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/LTC963 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
time-out period.
APPLICATI
s
s
s
s
S
Critical
µP
Power Monitoring
Intelligent Instruments
Battery-Powered Computers and Controllers
Automotive Systems
TYPICAL APPLICATI
V
IN
≥
7.5V
LT1086-5
V
IN
ADJ
V
OUT
5V
10µF
100µF
0.1µF
LTC692
LTC693
V
BATT
0.1µF
µP
SYSTEM
µP
RESET
µP
NMI
I/O LINE
LTC692/3 • TA01
RESET OUTPUT VOLTAGE (V)
+
+
V
CC
V
OUT
POWER TO
µP
CMOS RAM POWER
3V
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
100Ω
U
RESET Output Voltage vs
Supply Voltage
5
T
A
= 25°C
EXTERNAL PULL-UP = 10µA
V
BATT
= 0V
4
3
2
1
0
0
1
3
4
2
SUPPLY VOLTAGE (V)
5
LTC692/3 • TA02
UO
UO
1
LTC692/LTC693
ABSOLUTE
AXI U
RATI GS
(Notes 1 and 2)
V
OUT
Output Current .................. Short Circuit Protected
Power Dissipation............................................. 500mW
Operating Temperature Range
LTC692C/LTC693C ............................... 0°C to 70°C
LTC692I/LTC693I ............................ – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
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
PACKAGE/ORDER I FOR ATIO
TOP VIEW
V
OUT
1
V
CC
2
GND 3
PFI 4
N8 PACKAGE
8-LEAD PLASTIC DIP
8
7
6
5
V
BATT
RESET
WDI
PFO
ORDER PART
NUMBER
LTC692CN8
LTC692IN8
LTC692CS8
LTC692IS8
S8 PART MARKING
692
692I
S8 PACKAGE
8-LEAD PLASTIC SOIC
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
PRODUCT SELECTIO 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
2
U
U
W
W W
U
U
W
(Note 3)
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
16 RESET
15 RESET
14 WDO
13 CE IN
12 CE OUT
11 WDI
10 PFO
9
PFI
ORDER PART
NUMBER
LTC693CN
LTC693IN
LTC693CS
LTC693IS
N PACKAGE
S PACKAGE
16-LEAD PLASTIC DIP 16-LEAD PLASTIC SOL
T
JMAX
= 110°C,
θ
JA
= 130°C/W (N, S)
S16 Package Conditions: PCB Mount on FR4 Material,
Still Air at 25°C, Copper Trace
LTC692/LTC693
ELECTRICAL CHARACTERISTICS
V
CC
= Full Operating Range, V
BATT
= 2.8V, T
A
= 25°C, unless otherwise noted.
PARAMETER
Battery Backup Switching
Operating Voltage Range
V
CC
V
BATT
V
OUT
Output Voltage
I
OUT
= 1mA
q
CONDITONS
MIN
TYP
MAX
UNITS
4.50
2.00
V
CC
– 0.05
V
CC
– 0.10
V
CC
– 0.50
V
BATT
– 0.1
q
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
sec
sec
ms
ms
Clock
Cycles
ms/V
ms/V
ns
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)
Watchdog Time-Out Period,
Internal Oscillator
OSC SEL HIGH, V
CC
= 5V
q
q
I
OUT
= 250µA, V
CC
< V
BATT
I
OUT
≤
50mA
V
CC
= 0V, V
BATT
= 2.8V
q
5.5 > V
CC
> V
BATT
+ 0.2V
q
– 0.1
– 1.0
Power Up
Power Down
I
SINK
= 3.2mA
BATT ON = V
OUT
Sink Current
BATT ON = 0V Source Current
0.5
4.25
160
140
1.2
1.0
80
70
4032
960
35
1
4.40
40
200
200
1.6
1.6
100
100
25
4.50
240
280
2.00
2.25
120
140
4097
1025
Long Period, V
CC
= 5V
q
Short Period, V
CC
= 5V
q
Watchdog Time-Out Period, External Clock
(Note 6)
Reset Active Time PSRR
Watchdog Time-Out 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)
Long Period
Short Period
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
3.5
0.4
3.5
q
200
4
200
0.4
mV
V
V
V
V
3
LTC692/LTC693
ELECTRICAL CHARACTERISTICS
V
CC
= Full Operating Range, V
BATT
= 2.8V, T
A
= 25°C, unless otherwise noted.
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 Pullup 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
q
CONDITONS
Output Source Current
Output Sink Current
Logic Low
Logic High
WDI = V
OUT
WDI = 0V
V
CC
= 5V
q
q
MIN
1
TYP
3
25
MAX
25
0.8
UNITS
µA
mA
V
V
µA
µA
V
mV/V
nA
V
V
µA
mA
µs
µs
µs
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
±2
5
35
45
25
50
q
1.35
I
SINK
= 3.2mA
I
SOURCE
= 1µA
PFI = HIGH, PFO = 0V
PFI = LOW, PFO = V
OUT
∆V
IN
= –20mV, V
OD
= 15mV
∆V
IN
= 20mV, V
OD
= 15mV
with 10kΩ Pull-Up
V
IL
V
IH
V
V
µA
V
V
V
ns
ns
mA
mA
µA
µA
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
Output Source Current
Output Sink Current
OSC SEL = 0V
OSC SEL = 0V, C
OSC
= 47pF
q
0
4
250
kHz
kHz
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1:
Absolute maximum ratings are those values beyond which the life
of the device may be impaired.
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 time-out period is caused by phase errors which occur
when the oscillator divides the external clock by 64. The resulting variation
in the time-out 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.
4
LTC692/LTC693
TYPICAL PERFOR A CE CHARACTERISTICS
V
OUT
vs I
OUT
5.00
V
CC
= 5V
V
BATT
= 2.8V
T
A
= 25°C
2.80
V
CC
= 0V
V
BATT
= 2.8V
T
A
= 25°C
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
2.78
SLOPE = 125Ω
2.76
PFI INPUT THRESHOLD (V)
4.95
4.90
SLOPE = 5Ω
4.85
4.80
4.75
0
10
30
40
20
LOAD CURRENT (mA)
LTC692/3 • TPC01
Reset Active Time vs
Temperature
232
V
CC
= 5V
224
RESET ACTIVE TIME
216
208
200
192
184
–50 –25
4.41
PFO OUTPUT VOLTAGE (V)
RESET VOLTAGE THRESHOLD (V)
50
25
75
0
TEMPERATURE (°C)
LTC692/3 • TPC04
Power Fail Comparator
Response Time
PFO OUTPUT VOLTAGE (V)
PFO OUTPUT VOLTAGE (V)
6
5
4
3
2
1
0
V
PFI
1.3V
+
–
PFO
30pF
V
CC
= 5V
T
A
= 25°C
1.315V
1.295V
0
V
PFI
= 20mV STEP
20 40
U W
50
V
OUT
vs I
OUT
1.308
1.306
1.304
1.302
1.300
1.298
1.296
2.72
Power Failure Input Threshold
vs Temperature
V
CC
= 5V
2.74
0
100
300
400
200
LOAD CURRENT (µA)
500
1.294
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
LTC692/3 • TPC02
LTC692/3 • TPC03
Reset Voltage Threshold
vs Temperature
6
5
4
3
2
1
0
Power Fail Comparator
Response Time
V
CC
= 5V
T
A
= 25°C
V
PFI
1.3V
+
–
PFO
30pF
4.40
4.39
4.38
4.37
4.36
4.35
–50 –25
1.305V
1.285V
V
PFI
= 20mV STEP
100
125
50
25
75
0
TEMPERATURE (°C)
100
125
0
1
2
3 4 5
TIME (µs)
6
7
8
LTC692/3 • TPC05
LTC692/3 • TPC06
Power Fail Comparator Response
Time with Pull-Up Resistor
6
5
4
3
2
1
0
5V
V
PFI
1.3V
+
–
PFO
10k
30pF
V
CC
= 5V
T
A
= 25°C
1.315V
1.295V
0
2
V
PFI
= 20mV STEP
60 80 100 120 140 160 180
TIME (µs)
LTC692/3 • TPC07
4
6
8 10 12 14 16 18
TIME (µs)
LTC692/3 • TPC08
5
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