LTC699CN8 [Linear]
Microprocessor Supervisory Circuit; 微处理器监控电路
| 型号： | LTC699CN8 |
| 厂家： | 
Linear |
| 描述： | Microprocessor Supervisory Circuit |
| 文件： | 总4页 (文件大小：159K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC699
Microprocessor
Supervisory Circuit
U
DESCRIPTIO
EATURE
S
F
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■
■
■
■
■
■
■
Guaranteed Reset Assertion at VCC = 1V
1.5mA Maximum Supply Current
SO-8 Packaging
4.65V Precision Voltage Monitor
Power OK/Reset Time Delay: 200ms
Minimum External Component Count
Performance Specified Over Temperature
Superior Upgrade for MAX699
The LTC699 provides power supply monitoring for
microprocessor-based systems. The features include mi-
croprocessor reset and watchdog timing. Precise internal
voltage reference and comparator circuit monitor the
power supply line. When an out-of-tolerance condition
occurs, the RESET output is forced to active low. In
addition, the RESET output is guaranteed to remain logic
low even with VCC as low as 1V.
An internal watchdog timer is also available, which forces
the RESET output to active low when the watchdog input
is not toggled prior to the time-out period of 1.6 seconds.
O U
PPLICATI
S
A
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Critical µP Power Monitoring
Intelligent Instruments
Computers and Controllers
Automotive Systems
TheLTC699isofferedinDIPandsurfacemountpackages.
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O
W
TYPICAL APPLICATI
BLOCK DIAGRA
V
CC
+5V
500k
µP POWER
µP RESET
RESET
V
CC
RESET
+
RESET PULSE
C1
GENERATOR
–
µP
SYSTEM
LTC699
GND
1.3V
I/O LINE
WDI
GND
WATCHDOG
OSC
TIMER
0.1µF
0.1µF
TRANSITION
WDI
LTC699 TA1
DETECTOR
MICROPROCESSOR RESET AND WATCHDOG TIMING IN
A SINGLE CHIP FOR MICROPROCESSOR SYSTEMS.
LTC699 BD
1
LTC699
W
U
W W W
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ABSOLUTE AXI U RATI GS
/O
PACKAGE RDER I FOR ATIO
(Notes 1 and 2)
Terminal Voltage
TOP VIEW
ORDER PART
VCC ................................................... –0.3V to 6.0V
WDI Input .............................. –0.3V to VCC + 0.3V
RESET Output ...................................... –0.3V to 6V
Power Dissipation............................................. 500mW
Operating Temperature Range
NUMBER
V
V
1
2
3
4
8
7
6
GND
CC
RESET
WDI
CC
LTC699
LTC699CN8
LTC699IN8
GND
GND
5 NC
N8 PACKAGE
8-LEAD PLASTIC DIP
LTC699C .............................................. 0°C to 70°C
LTC699I ........................................... –40°C to 85°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec.)................ 300°C
TOP VIEW
LTC699CS8
LTC699IS8
V
1
2
3
4
8
7
6
5
GND
RESET
WDI
NC
CC
V
CC
LTC699
GND
GND
S8 PACKAGE
8-LEAD PLASTIC SOIC
VCC = +5V, TA = 25°C, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITONS
MIN
TYP
MAX
UNITS
Operating Voltage Range
Supply Current
●
3.0
5.5
1.5
2.5
4.75
4.75
V
mA
0.6
0.6
4.65
●
●
●
Power Down Reset Assertion
Power Up Reset De-Assertion
Reset Threshold Hysteresis
Reset Active Time
4.5
V
V
mV
ms
40
200
200
1.6
1.6
160
140
1.2
1.0
240
280
2.0
●
●
Watchdog Time-out Period
sec
2.25
Reset Active Time PSRR
Watchdog Time-out Period PSRR
Minimum WDI Input Pulse Width
1
8
ms/V
ms/V
ns
V
IL
= 0.4, V V = 3.5V
●
200
IH
RESET output Voltage at V = 1V (Note 3)
RESET output Voltage
I
I
= 10µA, V = 1V
= 1.6mA, V = 4.25V
CC
4
200
0.4
mV
V
CC
SINK
SINK
CC
RESET Output Short Circuit Current
WDI Input Threshold
Output Sink Current
Logic Low
Logic High
25
mA
V
0.8
50
2.0
WDI Input Current
WDI = V
●
●
4
–8
µA
OUT
WDI = 0V
–50
The
range.
●
denotes specifications which apply over the operating temperature
Note 2: All voltage values are with respect to GND.
Note 3: RESET is active low, open drain output.
Note 1: Absolute maximum ratings are those values beyond which the life
of device may be impaired.
2
LTC699
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PI FU CTIO S
VCC: +5V supply input. The VCC pin should be bypassed
with a 0.1µF capacitor.
but not serviced prior to the time-out period, the reset
pulsegeneratoralsoforcesRESETtoactivelowforamini-
mum of 140ms for every time-out period (see Figure 2).
GND: Ground pin.
WDI: Watchdog Input, WDI, is a three level input. Driving
WDI either high or low for longer than the watchdog time-
out period forces RESET low. Floating WDI disables the
WatchdogTimer.Thetimerresetsitselfwitheachtransition
of the Watchdog Input (see Figure 2).
RESET: Open drain output for µP reset control. When VCC
falls below the reset voltage threshold (4.65V typically),
RESET goes active low. After VCC returns to 5V, the reset
pulse generator forces RESET to remain active low for a
minimum of 140ms . When the watchdog timer is enabled
U W
TYPICAL PERFOR A CE CHARACTERISTICS
RESET Output Voltage vs
Supply Voltage
Reset Active Time vs
Temperature
Reset Voltage Threshold vs
Temperature
232
224
216
208
4.66
5
V
= 5V
T
= 25°C
CC
A
EXTERNAL PULLUP = 10µA
4.65
4.64
4.63
4.62
4
3
2
1
0
200
192
184
4.61
4.60
50
TEMPERATURE (
100
125
–50
25
50
75
C)
100 125
–50 –25
0
25
75
C)
–25
0
0
1
2
3
4
5
°
TEMPERATURE (
°
SUPPLY VOLTAGE (V)
LTC699 G01
LTC699 G02
LTC699 G03
O U
W
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PPLICATI
A
S I FOR ATIO
Microprocessor Reset
down, the RESET signal remains active low even with VCC
as low as 1V. This capability helps hold the microproces-
sor in stable shutdown condition. Figure 1 shows the
timing diagram of the RESET signal.
The LTC699 uses a bandgap voltage reference and a
precision voltage comparator C1 to monitor the 5V supply
input VCC (see BLOCK DIAGRAM). When VCC falls below
the reset voltage threshold, the RESET output is forced to
active low state. The reset voltage threshold accounts for
a 5% variation on VCC, so the RESET output becomes
active low when VCC falls below 4.65V typical. On power-
up, the RESET signal is held active low for a minimum of
140msafterresetvoltagethresholdisreachedtoallowthe
power supply and microprocessor to stabilize. On power-
The precision voltage comparator, C1, typically has 40mV
of hysteresis which ensures that glitches at VCC pin do not
activate the RESET output. Response time is typically
10µs.Tohelppreventmistriggeringduetotransientloads,
VCC pinshouldbebypassedwitha0.1µFcapacitorwiththe
leads trimmed as short as possible.
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-
tation that the interconnection of circuits as described herein will not infringe on existing patent rights.
3
LTC699
PPLICATI
O U
W
U
A
S
I FOR ATIO
V2
V2
V1
V1
V1 = RESET VOLTAGE THRESHOLD
V2 = RESET VOLTAGE THRESHOLD +
V
CC
RESET THRESHOLD HYSTERESIS
RESET
t1
t1
t1 = RESET ACTIVE TIME
LTC699 F01
Figure 1. Reset Active Time
Watchdog Timer
as RESET is inactive. When either a high-to-low or low-to-
high transition occurs at the WDI pin prior to time-out, the
watchdog time is reset and begins to time out again. To
ensure the watchdog time does not time out, either a high-
to-low or low-to-high transition on the WDI pin must
occur at or less than the minimum time-out period. If the
input to the WDI pin remains either high or low, reset
pulses will be issued every 1.6 seconds typically. The
watchdog time can be deactivated by floating the WDI pin.
The timer is also disabled when VCC falls below the reset
voltage threshold.
The LTC699 provides a watchdog timer function to moni-
tor the activity of the microprocessor. If the microproces-
sor does not toggle the Watchdog Input (WDI) within the
time-out period, RESET is forced to active low for a
minimum of 140ms. The watchdog time-out period is
fixed at a 1.0 second minimum on the LTC699, which is
adequate time for most systems to service 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 soon
V
= 5V
CC
WDI
t2
t2
t1
RESET
t1
t1
LTC699 F02
t1 = RESET ACTIVE TIME
t2 = WATCHDOG TIME-OUT PERIOD
Figure 2. Watchdog Time-Out Period and Reset Active Time
U
PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic SOIC
N8 Package
8-Lead Plastic DIP
D
D
8
7
6
5
B
1
E
8
7
2
6
3
5
4
h × 45°
A
1
C
A
B
A
Q
1
E
1
E
H
e
B
1
α
L
C
L
A
1
SYMBOL INCHES
MILLIMETERS SYMBOL INCHES
MILLIMETERS
1
1.270 TYP
0.228 – 0.244 5.791 – 6.198
A
A
B
C
D
E
0.053 – 0.069 1.346 – 1.753
0.102 – 0.254
e
0.050 TYP
S
N8 1191
e
A
H
h
L
α
0.004 – 0.010
1
e
1
0.014 – 0.019 0.356 – 0.483
0.008 – 0.010 0.203 – 0.254
0.189 – 0.197 4.801 – 5.004
0.150 – 0.157 3.810 – 3.988
0.010 – 0.020
0.016 – 0.050
0.254 – 0.508
0.406 – 1.270
0° – 8° TYP
1
2
3
4
S8 1191
MILLIMETERS SYMBOL INCHES
0.130 ± 0.006 3.302 ± 0.127
0.020 MIN
0.508 MIN
0.018 ± 0.003 0.457 ± 0.076
0.045 – 0.065 1.143 – 1.651
0.009 – 0.015 0.229 – 0.381
MILLIMETERS
6.350 ± 0.254
8.255 + 0.635
–0.381
2.540 ± 0.254
3.175 MIN
SYMBOL INCHES
A
A
B
B
C
D
E
E
0.250 ± 0.010
0.325 + 0.025
–0.015
0.100 ± 0.010
0.125 MIN
1
TJMAX
110°C 130°C/W
θJA
e
e
1
1
A
CONDITIONS: PCB MOUNT ON FR4 MATERIAL,
1
L
TJMAX
θJA
STILL AIR AT 25°C, COPPER TRACE
1.651 TYP
1.143 ± 0.381
110°C 180°C/W
0.400 MAX
10.160 MAX
0.300 – 0.320 7.620 – 8.128
Q
S
0.065 TYP
1
0.045 ± 0.015
LT/GP 0192 10K REV 0
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
4
●
●
LINEAR TECHNOLOGY CORPORATION 1992
(408) 432-1900 FAX: (408) 434-0507 TELEX: 499-3977
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