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LTC1235CN#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
LTC1235
1
1235fa
TYPICAL APPLICATION
DESCRIPTION
Microprocessor
Supervisory Circuit
Battery Life vs
Backup Duty Cycle
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
FEATURES
APPLICATIONS
n
Guaranteed Reset Assertion at V
CC
= 1V
n
1.5mA Maximum Supply Current
n
Fast (35ns Max.) Onboard Gating of RAM Chip
Enable Signals
n
Conditional Battery Backup Extends Battery Life
n
4.65V Precision Voltage Monitor
n
Power OK/Reset Time Delay: 200ms
n
External Reset Control
n
Minimum External Component Count
n
1μA Maximum Standby Current
n
Voltage Monitor for Power Fail or Low Battery
Warning
n
Thermal Limiting
n
Performance Specified Over Temperature
n
All the LTC695 Features Plus Conditional Battery
Backup and External Reset Control
n
Critical μP Power Monitoring
n
Intelligent Instruments
n
Battery-Powered Computers and Controllers
n
Automotive Systems
The LTC
®
1235 provides complete power supply monitoring
and battery control functions for microprocessor reset,
battery backup, RAM write protection, power failure warn-
ing and watchdog timing. The LTC1235 has all the LTC695
features plus conditional battery backup and external reset
control. When an out-of-tolerance power supply condition
occurs, the reset outputs are forced to active states and
the Chip Enable output write-protects external memory.
The RESET output is guaranteed to remain logic low with
V
CC
as low as 1V. External reset control is provided by a
debounced pushbutton reset input.
The LTC1235 powers the active CMOS RAMs with a charge
pumped NMOS power switch to achieve low dropout and
low supply current. When primary power is lost, auxiliary
power, connected to the battery input pin, provides backup
power to the RAMs. The LTC1235 can be programmed by
a P signal to either back up the R AMs or not. This ex tends
the battery life in situations where RAM data need not
always be saved when power goes down.
For an early warning of impending power failure, the
LTC1235 provides an internal comparator with a user-
defi ned 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 the time-out
period.
+
+
ADJ
V
IN
V
OUT
10μF
V
IN
≥ 7.5V
+5V
100μF
0.1μF
LTC1235
V
OUT
V
CC
V
BATT
PFI
WDI
μP NMI
μP
POWER
POWER TO
CMOS RAM
I/O LINE
μP RESET
μP
SYSTEM
0.1μF
+3V
51k
10k
1235 TA1
RESET
PFO
LT1086-5
THE LTC1235 EXTENDS BATTERY LIFE BY PROVIDING BATTERY POWER ONLY WHEN REQUIRED TO BACK UP RAM DATA.
IT SAVES THE BATTERY WHEN NO DATA BACKUP IS NEEDED. THE μP REQUESTS BACKUP WITH THE BACKUP PIN.
I/O LINE
BACKUP
PB RST
BACKUP DUTY CYCLE (%)
0
BATTERY LIFE (NORMALIZED)
6
8
10
80
1235 TA02
4
2
0
20
40
60
100
1
3
5
7
9
LTC1235
LTC695
(WITHOUT
CONDITIONAL
BATTERY
BACKUP)
LTC1235
2
1235fa
PIN CONFIGURATION
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage
V
CC
....................................................... –0.3V to 6.0V
V
BATT
.................................................... –0.3V to 6.0V
All Other Inputs ........................–0.3V to (V
CC
+ 0.3V)
Input Current
V
CC
..................................................................200mA
V
BATT
.................................................................50mA
(Notes 1 and 2)
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC1235CN#PBF LTC1235CN#TRPBF LTC1235CN 16-Lead Plastic DIP 0°C to 70°C
LTC1235CSW#PBF LTC1235CSW#TRPBF LTC1235CSW 16-Lead Plastic SOL 0°C to 70°C
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based fi nish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to:
http://www.linear.com/tapeandreel/
V
OUT
Output Current ...................Short Circuit Protected
Power Dissipation ...............................................500mW
Operating Temperature Range
LTC1235C ................................................ 0°C to 70°C
Storage Temperature Range ................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec.) ................. 300°C
1
2
3
4
5
6
7
8
TOP VIEW
WDO
V
CC
V
OUT
V
BATT
GND
LTC1235
CE IN
RESET
N PACKAGE
16-LEAD PLASTIC DIP
9
16
15
14
13
12
11
10
BATT ON
PB RST
LOW LINE
BACKUP
RESET
CE OUT
WDI
PFI
PFO
LTC1235
1
2
3
4
5
6
7
8
TOP VIEW
WDO
V
CC
V
OUT
V
BATT
GND
SW PACKAGE
16-LEAD PLASTIC SOL
CE IN
PRESET
9
16
15
14
13
12
11
10
BATT ON
PB RST
LOW LINE
BACKUP
PRESET
CE OUT
WDI
PFI
PFO
T
JMAX
= 110°C, θ
JA
= 130°C/W T
JMAX
= 110°C, θ
JA
= 130°C/W
CONDITIONS:PCB MOUNT ON FR4 MATERIAL,
STILL AIR AT 25°C COPPER TRACE
PRODUCT SELECTION GUIDE
PINS RESET
WATCHDOG
TIMER
BATTERY
BACKUP
POWER FAIL
WARNING
RAM WRITE
PROTECT
PUSH-BUTTON
RESET
CONDITIONAL
BATTERY BACKUP
LTC1235 16 X X X X X X X
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
3
1235fa
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Battery Backup Switching
Operating Voltage Range
V
CC
V
BATT
4.75
2.00
5.50
4.25
V
V
V
OUT
Output Voltage I
OUT
= 1mA
I
OUT
= 50mA
l
V
CC
– 0.05
V
CC
– 0.1
V
CC
– 0.5
V
CC
– 0.005
V
CC
– 0.005
V
CC
– 0.25
V
V
V
BACKUP Input Threshold V
CC
> Reset Voltage Threshold
Logic Low
Logic High 2.0
0.8 V
V
BACKUP Pullup Current (Note 4) 3μA
V
OUT
in Battery Backup Mode (Note 5) I
OUT
= 250μA, V
CC
< V
BATT
V
BATT
– 0.1 V
BATT
– 0.02 V
V
OUT
in Battery Saving Mode (Note 5) V
CC
< V
BATT
1MΩ Pulldown on V
OUT
0V
V
V
CC
Supply Current (excluding I
OUT
)I
OUT
≤ 50mA
l
0.6
0.6
1.5
2.5
mA
mA
Battery Supply Current in Battery Backup Mode
and Battery Saving Mode (Note 5)
V
CC
= 0V, V
BATT
= 2.8V
l
0.04
0.04
1
5
μA
μA
Battery Standby Current
(+ = Discharge, – = Charge)
5.5 > V
CC
> V
BATT
+ 0.2V
l
–0.1
–1.0
+0.02
+0.10
μA
μA
Battery Switchover Threshold
V
CC
– V
BATT
Power-Up
Power-Down
70
50
mV
mV
Battery Switchover Hysteresis 20 mV
BATT ON Output Voltage (Note 6) I
SINK
= 3.2mA 0.4 V
BATT ON Output Short Circuit Current (Note 6) BATT ON = V
OUT
Sink Current
BATT ON = 0V Source Current 0.5
35
125
mA
μA
Push-Button Reset
PB RST Input Threshold Logic Low
Logic High 2.0
0.8 V
V
PB RST Input Low Time (Notes 4, 7)
l
40 ms
Reset and Watchdog Timer
Reset Voltage Threshold
l
4.5 4.65 4.75 V
Reset Threshold Hysteresis 40 mV
Reset Active Time V
CC
= 5V
l
60
140
200
200
240
280
ms
ms
Watchdog Time-out Period V
CC
= 5V
l
1.2
1.0
1.6
1.6
2.00
2.25
sec
sec
Reset Active Time PSRR 1ms/V
Watchdog Time-out Period PSRR 8ms/V
Minimum WDI Input Pulse Width V
IL
= 0.4V, V
IH
= 3.5V
l
200 ns
RESET Output Voltage At V
CC
= 1V I
SINK
= 10μA, V
CC
= 1V 4 200 mV
RESET and LOW LINE Output Voltage
(Note 6)
I
SINK
= 1.6mA, V
CC
= 4.25V
I
SOURCE
= 1μA, V
CC
= 5V 3.5
0.4 V
V
RESET and WDO Output Voltage
(Note 6)
I
SINK
= 1.6mA, V
CC
= 5V
I
SOURCE
= 1μA, V
CC
= 4.25V 3.5
0.4 V
V
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
CC
= Full Operating Range, V
BATT
= 2.8V, Backup = No Connection,
T
A
= 25°C, unless otherwise noted.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16

LTC1235CN#PBF

Mfr. #:
Buy LTC1235CN#PBF
Manufacturer:
Analog Devices Inc.
Description:
Supervisory Circuits uP Supervisor with Watchdog and RAM Project
Lifecycle:
New from this manufacturer.
Delivery:
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