ANALOG DEVICES LTC 1232 CS8 Datasheet

FEATURES

■

Guaranteed

■

8-Pin SO Plastic Package

■

2.0mA Maximum Supply Current

■

4.62V/4.37V Precision Voltage Monitor

■

Power OK/Reset Time Delay: 600ms

■

Minimum External Component Count

■

Superior Upgrade for DS1232

Reset Assertion at VCC = 1V

LTC1232

Microprocessor

Supervisory Circuits

U

DESCRIPTIO

The LTC®1232 provides power supply monitoring,
watchdog timing and external reset for microprocessor
systems. 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. The RST output is guaranteed
to remain logic low even with V

as low as 1V.

CC

U

APPLICATIO S

■

Critical µP Power Monitoring

■

Intelligent Instruments

■

Computers and Controllers

■

Automotive Systems

TYPICAL APPLICATIO

5V DC

PB RST

TD

TOL

LTC1232

V

RST

CC

ST

U

5V DC

100k

(e.g. 6805)

I/O LINE

RESET

MPU

The LTC1232 has an internal watchdog timer which forces
the reset outputs to active states when the Strobe input is
not forced low prior to a preset time-out period. The
watchdog timing can be set to operate on time-out periods
of typically 150ms, 600ms or 1.2 seconds.

The LTC1232 performs push-button reset control.
The LTC1232 debounces the push-button input
and guarantees an active reset pulse width of 250ms
minimum.

, LTC and LT are registered trademarks of Linear Technology Corporation.

RST Output Voltage vs

Supply Voltage

5

4

3

2

GND

RST

LTC1232 • TA01

RST OUTPUT VOLTAGE (V)

1

0

1

0

SUPPLY VOLTAGE (V)

3

4

2

5

LTC1232 • TA02

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1

LTC1232

WWWU

ABSOLUTE AXI U RATI GS

(Note 1, 2 and 3)

Terminal Voltage

V

.......................................................–0.3V to 7.0V

CC

ST and RST .......................................... – 0.3V to 7.0V

All Other Inputs and Outputs ...... – 0.3V to V

Power Dissipation.............................................. 500mW

Operating Temperature Range

LTC1232C ............................................... 0°C to 70°C

LTC1232I ........................................... –40°C to 85°C

Storage Temperature Range ................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec).................. 300°C

+0.3V

CC

UU

W

PACKAGE/ORDER I FOR ATIO

TOP VIEW

PB RST

1

TD

2

TOL

3

GND

4

N8 PACKAGE
8-LEAD PDIP

= 100°C, θJA = 130°C/W

T

JMAX

TOP VIEW

PB RST

1

TD

2

TOL

3

GND

4

S8 PACKAGE

8-LEAD PLASTIC SO

T

= 100°C, θJA = 180°C/W

JMAX

Consult LTC Marketing for parts specified with wider operating tempera­ture ranges.

V

8

CC

ST

7

RST

6

RST

5

V

8

CC

ST

7

RST

6

RST

5

ORDER

PART NUMBER

LTC1232CN8

ORDER

PART NUMBER

LTC1232CS8
LTC1232IS8

S8 PART MARKING

1232
1232I

U

PRODUCT SELECTIO GUIDE

POWER RAM CONDITIONAL

WATCHDOG BATTERY FAIL WRITE PUSH-BUTTON BATTERY

PINS RESET TIMER BACKUP WARNING PROTECT RESET BACKUP

LTC1232 8 X X X

LTC690 8 X X X X

LTC691 16 X XXXX

LTC694 8 X X X X

LTC695 16 X XXXX

LTC699 8 X X

LTC1235 16 X XXXXX X

2

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LTC1232

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RECO E DED OPERATI G CO DITIO S

over the full operating temperature. V

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

CC

V

IH

V

IL

Supply Voltage ● 4.5 5 5.5 V

ST and PB RST Input High Level ● 2V

ST and PB RST Input Low Level ● – 0.3 0.8 V

DC ELECTRICAL CHARACTERISTICS

temperature. V

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

I

IL

I

OH

I

OL

I

CC

V

CCTP

V

CCTP

V

HYS

V

RST

= full operating range.

CC

Input Leakage (Note 3) ● –1 1 µA

Output Current at 2.4V (Note 5) ● –1 –13 mA

Output Current at 0.4V (Note 5) ● 26 mA

Supply Current (Note 4) ● 0.5 2 mA

VCC Trip Point TOL = GND ● 4.5 4.62 4.74 V

VCC Trip Point TOL = V

VCC Trip Point Hysteresis 40 mV

RST Output Voltage at VCC = 1V I

= full operating range.

CC

= 10µA 4 200 mV

SINK

The ● denotes the specifications which apply over the full operating

CC

UU UU

The ● denotes the specifications which apply

+0.3 V

CC

● 4.25 4.37 4.49 V

AC CHARACTERISTICS

The ● denotes the specifications which apply over the full operating temperature.

VCC = full operating range.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

t

PB

t

RST

t

ST

t

RPD

t

f

t

RPU

t

R

t

TD

C

IN

C

OUT

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

Note 2: All voltage values are with respect to GND.
Note 3: The PB RST pin is internally pulled up to VCC with an internal

impedance of 10k typical. The TD pin has internal bias current.

PB RST = V

RESET Active Time ● 250 610 1000 ms

ST Pulse Width ● 20 ns

VCC Detect to RST and RST ● 100 ns

VCC Slew Rate 4.75V–4.25V ● 300 µs

VCC Detect to RST and RST tR = 5µs ● 250 610 1000 ms
(Reset Active Time)

VCC Slew Rate 4.25V–4.75V ● 0ns

ST Pin Detect to RST and RST TD = GND ● 60 150 250 ms
(Watchdog Time-Out Period) TD = Floating

Input Capacitance 5pF

Output Capacitance 5 pF

IL

TD = V

CC

Note 4: Measured with outputs open.
Note 5: The RST pin is an open drain output.

● 40 ms

● 250 610 1000 ms

● 500 1200 2000 ms

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