LTC690/LTC691
LTC694/LTC695
Microprocessor
Supervisory Circuits
FEATURES
s
s
s
s
DESCRIPTIO
®
s
s
s
s
s
s
s
s
s
UL Recognized
File # E145770
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
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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
Critical
µP
Power Monitoring
Intelligent Instruments
Battery-Powered Computers and Controllers
Automotive Systems
TYPICAL APPLICATIO
LT
®
1086-5
V
IN
ADJ
V
OUT
V
IN
≥
7.5V
5V
10µF
100µF
0.1µF
LTC690/LTC691
LTC694/LTC695
V
BATT
RESET
PFO
PFI
GND WDI
0.1µF
0.1µF
µP
SYSTEM
µP
RESET
µP
NMI
I/O LINE
690 TA01
RESET OUTPUT VOLTAGE (V)
+
+
V
CC
V
OUT
POWER TO
µP
CMOS RAM POWER
3V
51k
10k
MICROPROCESSOR RESET, BATTERY BACK-UP, POWER FAILURE
WARNING AND WATCHDOG TIMING ARE ALL IN A SINGLE CHIP
FOR MICROPROCESSOR SYSTEMS
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
690 TA02
U
U
1
LTC690/LTC691
LTC694/LTC695
ABSOLUTE
AXI U
RATI GS
(Notes 1 and 2)
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
(Note 3)
TOP VIEW
V
BATT
1
V
OUT
2
16 RESET
15 RESET
14 WDO
13 CE IN
12 CE OUT
11 WDI
10 PFO
9 PFI
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
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
16 RESET
15 RESET
14 WDO
13 CE IN
12
CE OUT
ORDER PART
NUMBER
LTC691CN
LTC691IN
LTC695CN
LTC695IN
11 WDI
10 PFO
9
PFI
T
JMAX
= 110°C,
θ
JA
= 130°C/W
TOP VIEW
V
OUT
V
CC
GND
1
2
3
8
7
6
5
V
BATT
RESET
WDI
PFO
PFI 4
LTC690CN8
LTC690IN8
LTC690MJ8
LTC694CN8
LTC694IN8
J8 PACKAGE
N8 PACKAGE
8-LEAD CERDIP 8-LEAD PDIP
T
JMAX
= 110°C,
θ
JA
= 100°C/W (J8)
T
JMAX
= 110°C,
θ
JA
= 130°C/W (N8)
PRODUCT SELECTIO 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
PUSH-BUTTON
RESET
CONDITIONAL
BATTERY
BACK-UP
2
U
U
W
W W
U
U
W
ORDER PART
NUMBER
LTC691CSW
LTC691ISW
LTC695CSW
LTC695ISW
V
CC
3
GND 4
BATT ON 5
LOW LINE 6
OSC IN 7
OSC SEL 8
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
V
OUT
V
CC
GND
PFI
1
2
3
4
8
7
6
5
VBATT
RESET
WDI
PFO
LTC690CS8
LTC690IS8
LTC694CS8
LTC694IS8
S8 PART
MARKING
690 694
690I 694I
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
LTC690/LTC691
LTC694/LTC695
ELECTRICAL CHARACTERISTICS
PARAMETER
Battery Back-Up Switching
Operating Voltage Range
V
OUT
Output Voltage
V
CC
V
BATT
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.
CONDITONS
MIN
4.75
2.00
q
TYP
MAX
5.50
4.25
UNITS
V
V
V
V
V
V
I
OUT
= 1mA
I
OUT
= 50mA
V
CC
– 0.05
V
CC
– 0.10
V
CC
– 0.50
V
BATT
– 0.1
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
35
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
I
OUT
= 250µA, V
CC
< V
BATT
I
OUT
≤
50mA
q
mA
mA
µA
µA
µA
µA
mV
mV
mV
V
m
µA
V
V
mV
ms
ms
ms
ms
sec
sec
ms
ms
Clock
Cycles
ms/V
ms/V
ns
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
q
0.5
4.5
4.4
40
35
160
140
1.2
1.0
80
70
4032
960
1
4.65
4.65
40
50
50
200
200
1.6
1.6
100
100
25
4.75
4.75
60
70
240
280
2.00
2.25
120
140
4097
1025
LTC690M
Reset Threshold Hysteresis
Reset Active Time (LTC690/91) (Note 5)
Reset Active Time (LTC694/95) (Note 5)
Watchdog Time-Out Period, Internal Oscillator
OSC SEL HIGH, V
CC
= 5V
q
q
OSC SEL HIGH, V
CC
= 5V
q
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
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
V
IL
V
IH
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.
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
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
2.0
3
µA
0.4
V
OUT
– 1.50
V
OUT
– 0.05
q
50
q
1.35
V
mV/V
nA
V
µA
mA
µs
µs
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
25
V
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
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
20
20
30
35
±2
5
35
45
ns
mA
µA
µA
250
kHz
kHz
OSC SEL = 0V
OSC SEL = 0V, C
OSC
= 47pF
q
0
4
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 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 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.
4
LTC690/LTC691
LTC694/LTC695
BLOCK DIAGRA
VCC
VBATT
CE IN
–
C3
PFI
OSC IN
OSC
OSC SEL
+
PFO
RESET
RESET PULSE
GENERATOR
RESET
WATCHDOG
TIMER
WDO
690 BD
WDI
PI FU CTIO S
V
CC
:
5V Supply Input. The V
CC
pin should be bypassed
with a 0.1µF capacitor.
V
OUT
:
Voltage Output for Backed Up Memory. Bypass with
a capacitor of 0.1µF 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 5Ω. 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.
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.
W
M2
M1
VOUT
CHARGE
PUMP
–
C2
+
LOW LINE
+
C1
–
1.3V
BATT ON
CE OUT
GND
TRANSITION
DETECTOR
U
U
U
5
嵌入式系统
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
