LTC1232IS8#TR [Linear]
LTC1232 - Microprocessor Supervisory Circuit; Package: SO; Pins: 8; Temperature Range: -40°C to 85°C;
| 型号： | LTC1232IS8#TR |
| 厂家： | 
Linear |
| 描述： | LTC1232 - Microprocessor Supervisory Circuit; Package: SO; Pins: 8; Temperature Range: -40°C to 85°C 光电二极管 |
| 文件： | 总8页 (文件大小：93K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC1232
Microprocessor
Supervisory Circuits
U
FEATURES
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 VCC as low as 1V.
■
Guaranteed Reset Assertion at VCC = 1V
■
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
TheLTC1232hasaninternalwatchdogtimerwhichforces
the reset outputs to active states when the Strobe input is
not forced low prior to a preset time-out period. The
watchdogtimingcanbesettooperateontime-outperiods
of typically 150ms, 600ms or 1.2 seconds.
U
APPLICATIO S
■
Critical µP Power Monitoring
■
Intelligent Instruments
■
Computers and Controllers
The LTC1232 performs push-button reset control.
The LTC1232 debounces the push-button input
and guarantees an active reset pulse width of 250ms
minimum.
■
Automotive Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
TYPICAL APPLICATIO
RST Output Voltage vs
Supply Voltage
5
4
3
2
1
0
5V DC
MPU
PB RST
TD
V
CC
(e.g. 6805)
100k
ST
RST
RST
5V DC
I/O LINE
RESET
LTC1232
TOL
GND
LTC1232 • TA01
0
1
2
3
4
5
SUPPLY VOLTAGE (V)
LTC1232 • TA02
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1
LTC1232
W W
U W
U W
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ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Note 1, 2 and 3)
TOP VIEW
ORDER
PART NUMBER
Terminal Voltage
PB RST
TD
1
2
3
4
V
CC
8
7
6
5
V
CC .......................................................–0.3V to 7.0V
ST
ST and RST ..........................................–0.3V to 7.0V
All Other Inputs and Outputs ...... –0.3V to VCC +0.3V
Power Dissipation.............................................. 500mW
Operating Temperature Range
LTC1232CN8
LTC1232IN8
TOL
RST
RST
GND
N8 PACKAGE
8-LEAD PDIP
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
T
= 100°C, θ = 130°C/W
JMAX
JA
ORDER
TOP VIEW
PART NUMBER
PB RST
TD
1
2
3
4
8
7
6
5
V
CC
ST
LTC1232CS8
LTC1232IS8
TOL
RST
RST
GND
S8 PART MARKING
S8 PACKAGE
8-LEAD PLASTIC SO
= 100°C, θ = 180°C/W
1232
1232I
T
JMAX
JA
Consult LTC Marketing for parts specified with wider operating tempera-
ture ranges.
U
PRODUCT SELECTIO GUIDE
POWER
FAIL
WARNING
RAM
WRITE
PROTECT
CONDITIONAL
BATTERY
BACKUP
WATCHDOG
TIMER
BATTERY
BACKUP
PUSH-BUTTON
RESET
PINS
8
RESET
LTC1232
LTC690
LTC691
LTC694
LTC695
LTC699
LTC1235
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
8
X
X
X
X
X
X
X
X
16
8
X
X
X
16
8
16
X
X
X
X
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2
LTC1232
U
U
U
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W W
RECO E DED OPERATI G CO DITIO S
The ■ denotes the specifications which apply
over the full operating temperature. VCC = full operating range.
SYMBOL
PARAMETER
CONDITIONS
MIN
4.5
2
TYP
MAX
UNITS
V
V
V
Supply Voltage
■
■
■
5
5.5
V
V
V
CC
IH
IL
ST and PB RST Input High Level
ST and PB RST Input Low Level
V +0.3
CC
–0.3
0.8
DC ELECTRICAL CHARACTERISTICS
The ■ denotes the specifications which apply over the full operating
temperature. VCC = full operating range.
SYMBOL
PARAMETER
CONDITIONS
(Note 3)
MIN
–1
–1
2
TYP
MAX
UNITS
µA
I
I
I
I
Input Leakage
■
■
■
■
■
■
1
IL
Output Current at 2.4V
Output Current at 0.4V
Supply Current
(Note 5)
–13
6
mA
mA
mA
V
OH
OL
CC
(Note 5)
(Note 4)
0.5
4.62
4.37
40
2
V
V
V
V
V
CC
V
CC
V
CC
Trip Point
TOL = GND
4.5
4.74
4.49
CCTP
CCTP
HYS
Trip Point
TOL = V
4.25
V
CC
Trip Point Hysteresis
mV
mV
RST Output Voltage at V = 1V
I = 10µA
SINK
4
200
RST
CC
AC CHARACTERISTICS
The ■ denotes the specifications which apply over the full operating temperature.
VCC = full operating range.
SYMBOL PARAMETER
PB RST = V
CONDITIONS
MIN
40
TYP
MAX
1000
100
UNITS
ms
ms
ns
t
t
t
t
t
t
■
■
■
■
■
■
PB
IL
RESET Active Time
ST Pulse Width
250
20
610
RST
ST
V
V
V
Detect to RST and RST
Slew Rate 4.75V–4.25V
Detect to RST and RST
ns
RPD
f
CC
CC
CC
300
250
µs
t = 5µs
R
610
1000
ms
RPU
(Reset Active Time)
t
t
V
Slew Rate 4.25V–4.75V
■
0
ns
R
CC
ST Pin Detect to RST and RST
(Watchdog Time-Out Period)
TD = GND
TD = Floating
■
■
■
60
250
500
150
610
1200
250
1000
2000
ms
ms
ms
TD
TD = V
CC
C
C
Input Capacitance
Output Capacitance
5
5
pF
pF
IN
OUT
Note 4: Measured with outputs open.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 5: The RST pin is an open drain output.
Note 2: All voltage values are with respect to GND.
Note 3: The PB RST pin is internally pulled up to V with an internal
CC
impedance of 10k typical. The TD pin has internal bias current.
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3
LTC1232
W U
W
TI I G DIAGRA S
Push-Button Reset
Power Down
t
F
V
IH
PB RST
V
IL
4.75V
4.25V
V
4.50V
CC
t
t
RST
PB
RST
RST
t
RPD
V
V
IH
IL
RST
RST
V
V
OH
OL
LTC1232 • TD01
LTC1232 • TD03
Strobe Input
Power Up
t
t
R
ST
4.75V
4.25V
V
4.50V
CC
t
RPU
t
TD
RST
RST
LTC1232 • TD02
V
V
OH
OL
LTC1232 • TD04
W
BLOCK DIAGRA
8
3
V
CC
6
5
RST
RST
TOL
+
–
5%, 10%
SWITCH
RESET PULSE
GENERATOR
C1
1.3V
OSC
LEVEL SENSE
AND
WATCHDOG
TIMER
1
7
2
PB RST
ST
DEBOUNCE
LEVEL SENSE
TIME-OUT
SELECTION
TD
LTC1232 • BD01
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4
LTC1232
U W
TYPICAL PERFOR A CE CHARACTERISTICS
VCC Trip Point vs Temperature
VCC Trip Point vs Temperature
Reset Active Time vs Temperature
696
672
648
624
4.63
4.62
4.61
4.60
4.38
4.37
4.36
4.35
V
= 5V
TOL = V
TOL = GND
CC
CC
600
576
552
4.59
4.58
4.57
4.34
4.33
4.32
50
TEMPERATURE (˚C)
100 125
–50 –25
0
25
75
50
TEMPERATURE (˚C)
100 125
50
TEMPERATURE (˚C)
100 125
–50 –25
0
25
75
–50 –25
0
25
75
LTC1232 • TPC03
LTC1232 • TPC01
LTC1232 • TPC02
Time-Out Period vs Temperature
RST Output Voltage vs Supply Voltage
5
4
3
2
1
0
696
672
648
624
V
= 5V
T
= 25°C
CC
A
TD = NO CONNECTION
EXTERNAL PULL-UP = 10µA
600
576
552
0
1
2
3
4
5
50
TEMPERATURE (˚C)
100 125
–50 –25
0
25
75
SUPPLY VOLTAGE (V)
LTC1232 • TPC05
LTC1232 • TPC04
U
U
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PI FU CTIO S
TOL: Input to Select 5% or 10% Variation on VCC. When
TOL is connected to GND, the reset pulse generator forces
the reset outputs to active states as VCC falls below 4.75V
(4.62V typical). When TOL is connected to VCC, the reset
pulsegeneratorforcestheresetoutputstoactivestatesas
VCC falls below 4.5V (4.37V typical).
VCC: 5V Supply Input. The VCC pin should be bypassed
with a 0.1µF capacitor.
GND: Ground Pin.
PB RST: Logic Input to be Directly Connected to a Push-
Button. The PB RST input requires an active low signal
which is debounced and timed for a minimum of 40ms.
When this condition is satisfied, the reset pulse generator
forces the reset outputs to active states. The reset outputs
remain in active states for a minimum of 250ms after
PB RST is released from logic low level.
TD:Time-OutDelay.TDisathree-levelinputtoselectthree
different time-out periods. The time-out period is set by
the TD input to be 150ms with TD connected to GND,
600ms with TD left floating, and 1.2 seconds with TD
connected to VCC.
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5
LTC1232
U
U
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PI FU CTIO S
active low for a minimum of 250ms from the moment the
push-button reset input is released from logic low level.
RST: Open Drain Logic Output for µP Reset Control.
The LTC1232 provides three ways to generate µP reset.
First, when VCC falls below VCC trip point (4.75V with
TOL=GNDand4.5VwithTOL=VCC),RSTgoesactivelow.
After VCC returns to 5V, the reset pulse generator forces
RST to remain active low for a minimum of 250ms.
Second, when the watchdog timer is not serviced prior to
a selected time-out period, the reset pulse generator also
forces RST to active low for a minimum of 250ms and
repeats for every time-out period. Third and the last, when
the PB RST pin stays active low for a minimum of 40ms,
RST becomes active low. The RST output will remain
RST: RST is an Active High Logic Output. It is the inverse
of RST.
ST: Logic Input to Reset the Watchdog Timer. Driving ST
either high or low longer than the time-out period set by
the TD input, forces the reset outputs to active states for
a minimum of 250ms. The timer resets itself and begins to
time-out again with each high to low transition on the ST
input (see Figure 2).
W U U
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APPLICATIO S I FOR ATIO
Power Monitoring
The LTC1232 uses a bandgap voltage reference and a
precision voltage comparator, C1, to monitor the 5V
supply input on VCC (see Block Diagram). When VCC falls
below the VCC trip point (4.62V typical with
TOL = GND and 4.37V typical with TOL VCC), the reset
outputs are forced to active states. The VCC trip point
accounts for a 5% or 10% variation on VCC, so the reset
outputs become active when VCC falls below the VCC trip
point. On power-up, the reset signals are held in active
states for a minimum of 250ms after the VCC trip point is
reached to allow the power supply and microprocessor
to stabilize. On power-down, the RST signal remains
activelowevenwithVCC aslowas1V. Thiscapabilityhelps
hold the microprocessor in stable shutdown condition.
Figure 1 shows the timing diagram of the RST signal.
The precision voltage comparator, C1, typically has 40mV
of hysteresis which ensures that glitches at VCC pin do not
activatetheresetoutputs.Responsetimeistypically10µs.
To help prevent mitriggering due to transient loads, VCC
pin should be bypassed with a 0.1µF capacitor with the
leads trimmed as short as possible.
Push-Button Reset
The LTC1232 provides a logic input pin, PB RST, for direct
connectiontoapush-button. Thispush-buttonresetinput
requiresanactivelowsignal. Internally, thisinputsignalis
debounced and timed for a minimum of 40ms. When this
V2
CC
V2
V
V1
V1
t
t
1
1
RST
V1 = V TRIP POINT
CC
V2 = V TRIP POINT + V
CC HYS
t
= RESET ACTIVE TIME
1
LTC1232 • TA03
Figure 1. Reset Active Time
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6
LTC1232
W U U
APPLICATIO S I FOR ATIO
condition is satisfied, the reset pulse generator forces the
resetoutputstoactivestates. Theresetsignalswillremain
active for a minimum of 250ms from the moment the
push-button reset input is released from logic low level
(see Timing Diagram).
U
V
= 5V
CC
ST
t
t
t
t
t
1
1
2
1
2
RST
t
t
= RESET ACTIVE TIME
= WATCHDOG TIME-OUT PERIOD
1
2
Watchdog Timer
LTC1232 • TA04
The LTC1232 provides a watchdog timer function to
monitor the activity of the microprocessor. If the micro-
processor does not stimulate the strobe input, ST, within
a selected time-out period, the reset outputs are forced to
activestatesforaminimumof250ms.Thetime-outperiod
is selected by the Time-Out Delay input, TD, to be 150ms
with TD connected to GND, 600ms with TD left floating,
and1.2secondswithTDconnectedtoVCC.The1.2second
time-out period is adequate for many systems to serve the
watchdog timer immediately after a reset. Figure 2 shows
the timing diagram of watchdog time-out period and reset
active time. The watchdog time-out period is restarted as
Figure 2. Watchdog Time-Out Period and Reset Active Time
soon as the reset outputs are inactive. When a high-to-low
transition occurs at the ST pin prior to time-out, the
watchdog time is reset and begins to time-out again. To
ensurethewatchdogtimedoesnottime-out, ahigh-tolow
transition on the ST pin must occur at or less than the
minimum time-out period. If the input to the ST pin
remains either high or low, reset pulses will be issued for
every time-out period selected by the TD pin. The watch-
dog timer is disabled when VCC falls below the VCC trip
point.
U
PACKAGE DESCRIPTIO
N8 Package
8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
.400*
(10.160)
MAX
8
7
6
5
4
.255 ± .015*
(6.477 ± 0.381)
1
2
3
.130 ± .005
.300 – .325
.045 – .065
(3.302 ± 0.127)
(1.143 – 1.651)
(7.620 – 8.255)
.065
(1.651)
TYP
.009 – .015
(0.229 – 0.381)
.125
.020
(0.508)
MIN
(3.175)
MIN
+.035
.325
–.015
.018 ± .003
(0.457 ± 0.076)
.100
(2.54)
BSC
+0.889
8.255
(
)
N8 0502
–0.381
NOTE:
INCHES
1. DIMENSIONS ARE
MILLIMETERS
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
1232fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
7
LTC1232
U
PACKAGE DESCRIPTIO
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 – .197
(4.801 – 5.004)
.045 ±.005
NOTE 3
.050 BSC
N
7
5
8
6
N
.245
MIN
.160 ±.005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
1
2
3
N/2
N/2
4
.030 ±.005
TYP
RECOMMENDED SOLDER PAD LAYOUT
1
2
3
.010 – .020
(0.254 – 0.508)
× 45°
.053 – .069
(1.346 – 1.752)
.004 – .010
(0.101 – 0.254)
.008 – .010
(0.203 – 0.254)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
.050
(1.270)
BSC
.014 – .019
(0.355 – 0.483)
TYP
NOTE:
INCHES
1. DIMENSIONS IN
(MILLIMETERS)
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
SO8 0502
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DESCRIPTION
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Meets PCI t
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FAIL
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Adjustable RESET and Watchdog Time-Outs
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Individual Monitor Outputs in MSOP
5-Lead SOT-23 Package
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5-Lead SOT-23 Package
1232fa
LW/TP 1002 1K REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
8
■
■
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
LINEAR TECHNOLOGY CORPORATION 1992
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