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PDF LTC1727EMS8-5 Data sheet ( Hoja de datos )
| Número de pieza | LTC1727EMS8-5 | |
| Descripción | Micropower Precision Triple Supply Monitors in 8-Lead MSOP and 5-Lead SOT-23 Packages | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
s Monitors Three Inputs Simultaneously
LTC1727-5: 5V, 3.3V and ADJ
LTC1727-2.5: 2.5V, 3.3V and ADJ
LTC1728-5: 5V, 3.3V and ADJ
LTC1728-2.5: 2.5V, 3.3V and ADJ
LTC1728-1.8: 3V, 1.8V and ADJ
s ±1.5% Threshold Accuracy Over Temperature
s Very Low Supply Current: 10µA Typ
s 200ms Reset Time Delay
s Active Low RESET Output
s Power Supply Glitch Immunity
s Guaranteed RESET for VCC3 ≥ 1V
or VCC5/VCC25/VCC18 ≥ 1V
s LTC1727 Includes Monitor Output for Each Supply
s LTC1727: 8-Lead MSOP and SO Packages
s LTC1728: 5-Lead SOT-23 Package
U
APPLICATIO S
s Desktop Computers
s Notebook Computers
s Intelligent Instruments
s Portable Battery-Powered Equipment
s Network Servers
LTC1727/LTC1728
Micropower Precision
Triple Supply Monitors
in 8-Lead MSOP and
5-Lead SOT-23 Packages
DESCRIPTIO
The LTC®1727 is a triple supply monitor intended for
systems with multiple supply voltages. Each supply moni-
tor has its own open-drain output for individual supply
monitoring. A common open-drain reset output remains
low until all three supplies have been in compliance for
200ms. Tight 1.5% accuracy specifications and glitch
immunity ensure reliable reset operation without false
triggering.
The LTC1728 is functionally identical to the LTC1727
without the individual monitor outputs.
The RST output is guaranteed to be in the correct state for
VCC5/VCC25/VCC18 or VCC3 down to 1V. The LTC1727/
LTC1728 may also be configured to monitor any one or
two VCC inputs instead of three, depending on system
requirements.
Very low (10µA typical) supply current makes the LTC1727/
LTC1728 ideal for power conscious systems.
The LTC1727 is available in an 8-lead MSOP or SO
package and the LTC1728 is available in a 5-lead SOT-23
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
3.3V
DC/DC 5V
CONVERTER 1.8V
SYSTEM
LOGIC
0.1µF
0.1µF
5
VCC3
1
RST
4
R1
61.9k
1% 3
R2
100k
1%
LTC1728-5
VCC5
VCCA
2
GND
1727/28 TA01
Triple Supply Monitor with Power Good Output
(3.3V, 2.5V and Adjustable)
ADJUSTABLE
SUPPLY
3.3V
2.5V
R1
R2
LTC1727-2.5
18
VCC3 COMP3
R3
10k
27
VCC25 COMP25
3
VCCA
6
RST
4
GND
COMPA 5
1727/28 TA08
R4
10k
POWER
GOOD
SYSTEM
RESET
1
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
LTC1727/LTC1728
VCC25 Threshold Voltage
vs Temperature
(LTC1727-2.5/LTC1728-2.5)
2.3750
2.3675
2.3600
2.3525
2.3450
2.3375
2.3300
2.3225
2.3150
2.3075
2.3000
– 60 –40 – 20 0 20 40 60 80 100
TEMPERATURE (°C)
1727/28 G10
VCC3 Threshold Voltage
vs Temperature
(All But LTC1728-1.8)
3.135
3.125
3.115
3.105
3.095
3.085
3.075
3.065
3.055
3.045
3.035
– 60 –40 – 20 0 20 40 60 80 100
TEMPERATURE (°C)
1727/28 G11
VCC5 Threshold Voltage
vs Temperature
(LTC1727-5/LTC1728-5)
4.750
4.725
4.700
4.675
4.650
4.625
4.600
–60 –40 –20 0 20 40 60
TEMPERATURE (°C)
80 100
1727/28 G12
IVCC18 vs Temperature
(LTC1728-1.8)
1.5
VCC3 = 3V
1.4 VCC18 = 1.8V
1.3 VCCA = 3V
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
– 60 –40 – 20 0 20 40 60 80 100
TEMPERATURE (°C)
1727/28 G13
IVCC3 vs Temperature
(LTC1728-1.8)
15
VCC3 = 3V
14 VCC18 = 1.8V
13 VCCA = 3V
12
11
10
9
8
7
6
5
– 60 –40 – 20 0 20 40 60
TEMPERATURE (°C)
80 100
1727/28 G14
VCC18 Threshold Voltage
vs Temperature (LTC1728-1.8)
1.710
1.700
1.690
1.680
1.670
1.660
1.650
–60 –40 –20 0 20 40 60
TEMPERATURE (°C)
80 100
1727/28 G15
VCC3 Threshold Voltage
vs Temperature (LTC1728-1.8)
2.845
2.835
2.825
2.815
2.805
2.795
2.785
2.775
2.765
– 60 –40 – 20 0 20 40 60
TEMPERATURE (°C)
80 100
1727/28 G16
5
5 Page 
LTC1727/LTC1728
APPLICATIO S I FOR ATIO
Figure 4 contains a simple circuit for 5V systems that can’t
risk the RST output going high in the 3.1V to 4.15V range
(possibly due to very slow rise time on the 5V supply).
Diode D1 powers the LTC1728-5 while dropping ≈ 0.6V
from the VCC5 pin to the VCC3 pin. This prevents the part’s
internal override circuit from being activated. Without the
override circuit active, the RST pin stays low until VCC5
reaches VRT5 ≅ 4.675V. (See Figure 5.)
LTC1727-2.5/LTC1728-2.5/LTC1728-1.8
Override Functions
The VCCA pin, if unused, can be tied to either VCC3 or VCC25/
VCC18. This is an obvious solution since the trip points for
VCC3 and VCC25/VCC18 will always be greater than the trip
point for VCCA. Likewise, the VCC25/VCC18, if unused, can
be tied to VCC3. VCC3 must always be used. Tying VCC3 to
VCC25/VCC18 and operating off of a 2.5V/1.8V supply will
result in the continuous assertion of RST.
5V
0.1µF
D1 LTC1728-5
5
VCC3
4
VCC5
31
VCCA
RST
2
GND
R1
10k
TO SYSTEM
RESET
D1: MMBD914 OR EQUIVALENT
1727/28 F04
Figure 4. LTC1728-5 Monitoring a Single 5V
Supply. D1 Used to Avoid RST High Near 3.1V
to 4V (See Figure 3).
5
VCC5 = VCCA = 0V TO 5V
10k PULL-UP FROM RST TO VCC5
4 TA = 25°C
3
2
1
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
VCC5 (V)
1727/28 F05
Figure 5. RST Output Voltage
Characteristics of the Circuit in Figure 4
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC1727EMS8-5.PDF ] | |
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