1
LTC690/LTC691
LTC694/LTC695
Microprocessor
Supervisory Circuits
ADJ
V
IN
V
OUT
10
F
V
IN
7.5V
5V
100
F
0.1
F
P NMI
P
POWER
POWER TO
CMOS RAM
I/O LINE
P RESET
P
SYSTEM
0.1
F
3V
51k
10k
690 TA01
LT
1086-5
MICROPROCESSOR RESET, BATTERY BACK-UP, POWER FAILURE
WARNING AND WATCHDOG TIMING ARE ALL IN A SINGLE CHIP
FOR MICROPROCESSOR SYSTEMS
LTC690/LTC691
LTC694/LTC695
V
BATT
PFI
WDI
RESET
PFO
V
OUT
V
CC
GND
0.1
F
100
+
+
RESET Output Voltage vs
Supply Voltage
s
UL Recognized File # E145770
s
Guaranteed Reset Assertion at V
CC
= 1V
s
1.5mA Maximum Supply Current
s
Fast (35ns Max) Onboard Gating of RAM Chip
Enable Signals
s
SO-8 and S16 Packaging
s
4.65V Precision Voltage Monitor
s
Power OK/Reset Time Delay: 50ms, 200ms
or Adjustable
s
Minimum External Component Count
s
1
A Maximum Standby Current
s
Voltage Monitor for Power-Fail
or Low-Battery Warning
s
Thermal Limiting
s
Performance Specified Over Temperature
s
Superior Upgrade for MAX690 Family
The LTC
690 family provides complete power supply
monitoring and battery control functions for microproces-
sor 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 time-out
period.
s
Critical
P Power Monitoring
s
Intelligent Instruments
s
Battery-Powered Computers and Controllers
s
Automotive Systems
SUPPLY VOLTAGE (V)
0
RESET OUTPUT VOLTAGE (V)
3
4
5
4
2
1
0
1
2
3
5
T
A
= 25
C
EXTERNAL PULL-UP = 10
A
V
BATT
= 0V
690 TA02
, LTC and LT are registered trademarks of Linear Technology Corporation.
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LTC690/LTC691
LTC694/LTC695
A
U
G
W
A
W
U
W
A
R
BSOLUTE
XI
TI
S
(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
LTC690M ...................................... 55
C to 125
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec.)................ 300
C
W
U
U
PACKAGE/ORDER I FOR ATIO
LTC691CSW
LTC691ISW
LTC695CSW
LTC695ISW
LTC691CN
LTC691IN
LTC695CN
LTC695IN
TOP VIEW
SW PACKAGE
16-LEAD WIDE PLASTIC SO
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
BATT
V
OUT
V
CC
GND
BATT ON
LOW LINE
OSC IN
OSC SEL
RESET
RESET
WDO
CE IN
CE OUT
WDI
PFO
PFI
T
JMAX
= 110
C,
JA
= 130
C/W Conditions: PCB mount on
FR4 Material, Still Air at 25
C, Copper Trace
1
2
3
4
5
6
7
8
TOP VIEW
N PACKAGE
16-LEAD PDIP
9
16
15
14
13
12
11
10
V
CC
V
OUT
V
BATT
GND
BATT ON
OSC IN
LOW LINE
OSC SEL
WDO
CE IN
RESET
RESET
CE OUT
WDI
PFI
PFO
T
JMAX
= 110
C,
JA
= 130
C/W
LTC690CN8
LTC690IN8
LTC690MJ8
LTC694CN8
LTC694IN8
LTC690CS8
LTC690IS8
LTC694CS8
LTC694IS8
S8 PART
MARKING
690
690I
694
694I
T
JMAX
= 110
C,
JA
= 100
C/W (J8)
T
JMAX
= 110
C,
JA
= 130
C/W (N8)
1
2
3
4
5
6
7
8
TOP VIEW
V
CC
V
OUT
PFI
GND
WDI
V
BATT
PFO
RESET
N8 PACKAGE
8-LEAD PDIP
J8 PACKAGE
8-LEAD CERDIP
(Note 3)
ORDER PART
NUMBER
ORDER PART
NUMBER
PRODUCT SELECTIO GUIDE
U
CONDITIONAL
WATCHDOG
BATTERY
POWER-FAIL
RAM WRITE
PUSH-BUTTON
BATTERY
PINS
RESET
TIMER
BACK-UP
WARNING
PROTECT
RESET
BACK-UP
LTC690
8
X
X
X
X
LTC691
16
X
X
X
X
X
LTC694
8
X
X
X
X
LTC695
16
X
X
X
X
X
LTC699
8
X
X
LTC1232
8
X
X
X
LTC1235
16
X
X
X
X
X
X
X
1
2
3
4
5
6
7
8
TOP VIEW
VBATT
V
CC
V
OUT
PFO
PFI
GND
S8 PACKAGE
8-LEAD PLASTIC SO
WDI
RESET
T
JMAX
= 110
C,
JA
= 180
C/W Conditions: PCB Mount on
FR4 Material, Still Air AT 25
C, Copper Trace
3
LTC690/LTC691
LTC694/LTC695
ELECTRICAL C
C
HARA TERISTICS
The
q
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.
PARAMETER
CONDITONS
MIN
TYP
MAX
UNITS
Battery Back-Up Switching
Operating Voltage Range
V
CC
4.75
5.50
V
V
BATT
2.00
4.25
V
V
OUT
Output Voltage
I
OUT
= 1mA
V
CC
0.05
V
CC
0.005
V
q
V
CC
0.10
V
CC
0.005
V
I
OUT
= 50mA
V
CC
0.50
V
CC
0.250
V
V
OUT
in Battery Back-Up Mode
I
OUT
= 250
A, V
CC
< V
BATT
V
BATT
0.1
V
BATT
0.02
V
Supply Current (Exclude I
OUT
)
I
OUT
50mA
0.6
1.5
mA
q
0.6
2.5
mA
Supply Current in Battery Back-Up Mode
V
CC
= 0V, V
BATT
= 2.8V
0.04
1
A
q
0.04
5
A
Battery Standby Current (+ = Discharge, = Charge)
5.5 > V
CC
> V
BATT
+ 0.2V
0.1
+ 0.02
A
q
1.0
+ 0.10
A
Battery Switchover Threshold, V
CC
V
BATT
Power Up
70
mV
Power Down
50
mV
Battery Switchover Hysteresis
20
mV
BATT ON Output Voltage (Note 4)
I
SINK
= 3.2mA
0.4
V
BATT ON Output Short-Circuit Current (Note 4)
BATT ON = V
OUT
Sink Current
35
m
BATT ON = 0V Source Current
0.5
1
25
A
Reset and Watchdog Timer
Reset Voltage Threshold
q
4.5
4.65
4.75
V
LTC690M
q
4.4
4.65
4.75
V
Reset Threshold Hysteresis
40
mV
Reset Active Time (LTC690/91) (Note 5)
OSC SEL HIGH, V
CC
= 5V
40
50
60
ms
q
35
50
70
ms
Reset Active Time (LTC694/95) (Note 5)
OSC SEL HIGH, V
CC
= 5V
160
200
240
ms
q
140
200
280
ms
Watchdog Time-Out Period, Internal Oscillator
Long Period, V
CC
= 5V
1.2
1.6
2.00
sec
q
1.0
1.6
2.25
sec
Short Period, V
CC
= 5V
80
100
120
ms
q
70
100
140
ms
Watchdog Time-Out Period, External Clock (Note 6)
Long Period
4032
4097
Clock
Short Period
960
1025
Cycles
Reset Active Time PSRR
1
ms/V
Watchdog Time-Out Period PSRR, Internal OSC
1
ms/V
Minimum WDI Input Pulse Width
V
IL
= 0.4V, V
IH
= 3.5V
q
200
ns
RESET Output Voltage at V
CC
= 1V
I
SINK
= 10
A, V
CC
= 1V
4
200
mV
RESET and LOW LINE Output Voltage (Note 4)
I
SINK
= 1.6mA, V
CC
= 4.25V
0.4
V
I
SOURCE
= 1
A, V
CC
= 5V
3.5
V
RESET and WDO Output Voltage (Note 4)
I
SINK
= 1.6mA, V
CC
= 5V
0.4
V
I
SOURCE
= 1
A, V
CC
= 4.25V
3.5
V
4
LTC690/LTC691
LTC694/LTC695
ELECTRICAL C
C
HARA TERISTICS
The
q
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.
PARAMETER
CONDITONS
MIN
TYP
MAX
UNITS
RESET, RESET, WDO, LOW LINE
Output Source Current
1
3
25
A
Output Short-Circuit Current (Note 4)
Output Sink Current
25
mA
WDI Input Threshold
Logic Low
0.8
V
Logic High
3.5
WDI Input Current
WDI = V
OUT
q
4
50
A
WDI = 0V
q
50
8
Power-Fail Detector
PFI Input Threshold
V
CC
= 5V
q
1.25
1.3
1.35
V
PFI Input Threshold PSRR
0.3
mV/V
PFI Input Current
0.01
25
nA
PFO Output Voltage (Note 4)
I
SINK
= 3.2mA
0.4
V
I
SOURCE
= 1
A
3.5
PFO Short-Circuit Source Current (Note 4)
PFI = HIGH, PFO = 0V
1
3
25
A
PFI = LOW, PFO = V
OUT
25
mA
PFI Comparator Response Time (Falling)
V
IN
= 20mV, V
OD
= 15mV
2
s
PFI Comparator Response Time (Rising) (Note 4)
V
IN
= 20mV, V
OD
= 15mV
40
s
with 10k
Pull-Up
8
Chip Enable Gating
CE IN Threshold
V
IL
0.8
V
V
IH
2.0
CE IN Pull-Up Current (Note 7)
3
A
CE OUT Output Voltage
I
SINK
= 3.2mA
0.4
V
I
SOURCE
= 3.0mA
V
OUT
1.50
I
SOURCE
= 1
A, V
CC
= 0V
V
OUT
0.05
CE Propagation Delay
V
CC
= 5V, C
L
= 20pF
20
35
ns
q
20
45
CE OUT Output Short-Circuit Current
Output Source Current
30
mA
Output Sink Current
35
Oscillator
OSC IN Input Current (Note 7)
2
A
OSC SEL Input Pull-Up Current (Note 7)
5
A
OSC IN Frequency Range
OSC SEL = 0V
q
0
250
kHz
OSC IN Frequency with External Capacitor
OSC SEL = 0V, C
OSC
= 47pF
4
kHz
Note 1: Absolute Maximum Ratings are those values beyond which the life
of device may be impaired.
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 3
A. 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 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
pullups which pull to the supply when the input pins are floating.
5
LTC690/LTC691
LTC694/LTC695
V
CC
: 5V Supply Input. The V
CC
pin should be bypassed
with a 0.1
F capacitor.
V
OUT
: Voltage Output for Backed Up Memory. Bypass with
a capacitor of 0.1
F or greater. During normal operation,
V
OUT
obtains power from V
CC
through an NMOS power
switch, M1, which can deliver up to 50mA and has a typical
on resistance of 5
. When V
CC
is lower than V
BATT
, V
OUT
is internally switched to V
BATT
. If V
OUT
and V
BATT
are not
used, connect V
OUT
to V
CC
.
V
BATT
: Back-Up Battery Input. When V
CC
falls below V
BATT
,
auxiliary power, connected to V
BATT
, is delivered to V
OUT
through PMOS switch, M2. If back-up battery or auxiliary
power is not used, V
BATT
should be connected to GND.
W
I
D AGRA
BLOCK
GND: Ground pin.
BATT ON: Battery On Logic Output from Comparator C2.
BATT ON goes low when V
OUT
is internally connected to
V
CC
. The output typically sinks 35mA and can provide base
drive for an external PNP transistor to increase the output
current above the 50mA rating of V
OUT
. BATT ON goes
high when V
OUT
is internally switched to V
BATT
.
PFI: Power Failure Input. PFI is the noninverting input to
the power-fail comparator, C3. The inverting input is
internally connected to a 1.3V reference. The power failure
output remains high when PFI is above 1.3V and goes low
when PFI is below 1.3V. Connect PFI to GND or V
OUT
when
C3 is not used.
PI FU CTIO S
U
U
U
CHARGE
PUMP
M2
M1
VBATT
VCC
CE IN
PFI
OSC IN
OSC SEL
WDI
RESET PULSE
GENERATOR
WATCHDOG
TIMER
RESET
BATT ON
VOUT
C1
1.3V
GND
+
+
C2
OSC
TRANSITION
DETECTOR
+
C3
WDO
RESET
PFO
LOW LINE
CE OUT
690 BD
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