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PDF LTC1726EMS8-5 Data sheet ( Hoja de datos )
| Número de pieza | LTC1726EMS8-5 | |
| Descripción | Triple Supply Monitor and uP Supervisor with Adjustable Reset and Watchdog Timer | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Final Electrical Specifications
LTC1726
Triple Supply Monitor and
µP Supervisor with Adjustable
Reset and Watchdog Timer
January 2000
FEATURES
s Monitors Three Inputs Simultaneously
LTC1726-5: 5V, 3.3V and ADJ
LTC1726-2.5: 2.5V, 3.3V and ADJ
s ±1.5% Threshold Accuracy Over Temperature
s Low Supply Current: 16µA Typ
s Adjustable Reset Timeout
s Adjustable Watchdog Timeout
s Active Low Open-Drain Reset Output
s Power Supply Glitch Immunity
s Guaranteed RESET for VCC3 ≥ 1V or VCC25/VCC5 ≥ 1V
s MS8 and SO-8 Packages
DESCRIPTIO
s Desktop Computers
s Notebook Computers
s Intelligent Instruments
s Portable Battery-Powered Equipment
s Network Servers
DESCRIPTIO
The LTC®1726 is a triple supply monitor and microproces-
sor supervisory circuit with adjustable reset and watchdog
functions intended for systems with multiple supply volt-
ages. The part has a common open-drain reset output with
an adjustable delay. The reset and watchdog time-out
periods are both adjustable using external capacitors.
Tight 1.5% accuracy specifications and glitch immunity
ensure reliable reset operation without false triggering.
The RST output is guaranteed to be in the correct state for
VCC5/VCC25 or VCC3 down to 1V. The LTC1726 may also be
configured to monitor any one or two VCC inputs instead
of three, depending on system requirements.
The low (16µA typical) supply current makes the LTC1726
ideal for power-conscious systems.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO S
A 3.3V, 5V and 1.8V Monitor
3.3V
0.1µF
5V
0.1µF
1.8V
(VTRIP = 1.665V)
R1
66.5k
1%
CRT
47nF
8
CWT
47nF
7
213
VCC5 VCC3 VCCA
RT RST
LTC1726-5
WT WDI
6
5
R2
100k
1%
RESET
µP
I/O
tRT = 155ms
tWT= 1s
GND
4
1726 TA01
A 3.3V, 2.5V and 1.8V Monitor
3.3V
0.1µF
2.5V
0.1µF
1.8V
(VTRIP = 1.665V)
R1
66.5k
1%
CRT
47nF
8
CWT
47nF
7
21 3
VCC25 VCC3 VCCA
RT RST
LTC1726-2.5
WT WDI
6
5
R2
100k
1%
RESET
µP
I/O
tRT = 155ms
tWT= 1s
GND
4
1726 TA02
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 its circuits as described herein will not infringe on existing patent rights.
1
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
LTC1726
Time-Out Period vs Capacitance
106
TA = 25°C
105
104 tWT
103 tRT
102
10
0.1
1 10 102 103
CRT OR CWT (pF)
104
1726 G12
RST Output Voltage vs
Supply Voltage (LTC1726-2.5)
VCC3 = VCC25 = VCCA
3
10k PULL-UP FROM VCC3 TO RST
TA = 25°C
2
1
0
0 12
3
VCC3 (V)
1726 F13
PI FU CTIO S
VCC3 (Pin 1): 3.3V Sense Input. This pin also supplies
power to the part when the voltage on this pin is greater
than the voltage on VCC25/VCC5. Bypass this pin to ground
with a 0.1µF or larger ceramic capacitor.
VCC5 (Pin 2): 5V Sense Input (LTC1726-5). This pin also
supplies power to the part when the voltage on this pin is
greater than the voltage on VCC3. Bypass this pin to
ground with a 0.1µF or larger ceramic capacitor.
VCC25 (Pin 2): 2.5V Sense Input (LTC1726-2.5). This pin
also supplies power to the part when the voltage on this
pin is greater than the voltage on VCC3. Bypass this pin to
ground with a 0.1µF or larger ceramic capacitor.
VCCA (Pin 3): 1V Sense, High Impedance Input. If unused
it can be tied to either VCC3, VCC5 or VCC25.
GND (Pin 4): Ground.
WDI (Pin 5): Watchdog Input. A logic input whose rising
or falling edge must occur on this pin within the selected
watchdog time-out period or a reset pulse will occur. The
watchdog time-out period is set by the value of the
capacitor that is placed on the WT pin. The rising or falling
edge of this pin clears the voltage on the WT capacitor,
preventing a reset pulse from occurring. If the watchdog
timer is not cleared, a reset pulse will occur. The watch-
dog timer is cleared during a reset and restarts when the
reset is deasserted. When disabling the watchdog func-
tion, this pin should be connected to either VCC3 or
ground and WT must be grounded.
RST (Pin 6): Reset Logic Output. Active low, open-drain
logic output with weak pull-up to VCC3. Asserted when
one or more of the supplies are below trip thresholds.
After all supplies become valid, the reset remains as-
serted for the period set by the capacitor on the RT pin.
The watchdog timer can also trigger the reset whenever
the watchdog time-out period is exceeded. This pin can
be pulled up greater than VCC3 when interfacing to 5V
logic.
WT (Pin 7): Watchdog Time-Out Input. Place a capacitor
between this pin and ground to adjust the watchdog time-
out period. To determine the watchdog time-out period:
tWT = 21.8 • CWT
with tWT in µs and CWT in pF. As an example, a 47nF
capacitor will generate a 1s watchdog time-out period.
The watchdog function can be disabled by connecting
this pin to ground.
5
5 Page 
PACKAGE DESCRIPTIO
Dimensions in (inches) unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.118 ± 0.004*
(3.00 ± 0.102)
8 76 5
0.193 ± 0.006
(4.90 ± 0.15)
0.118 ± 0.004**
(3.00 ± 0.102)
LTC1726
1 234
0.007
(0.18)
0° – 6° TYP
0.021 ± 0.006
(0.53 ± 0.015)
0.040 ± 0.006
(1.02 ± 0.15)
SEATING
PLANE
0.012
(0.30)
REF
0.0256
(0.65)
BSC
0.034 ± 0.004
(0.86 ± 0.102)
0.006 ± 0.004
(0.15 ± 0.102)
MSOP (MS8) 1098
* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
8 765
0.228 – 0.244
(5.791 – 6.197)
0.150 – 0.157**
(3.810 – 3.988)
12
0.010
(0.254
–
–
0.020
0.508)
×
45°
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.355 – 0.483)
TYP
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
34
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
SO8 1298
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC1726EMS8-5.PDF ] | |
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