LTC2908
Precision
Six Input Supply Monitor
FEATURES
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DESCRIPTION
The LTC
®
2908 is a six input supply monitor for systems
requiring a precise and compact monitoring solution
for multiple supply voltages. The inputs can be shorted
together for monitoring systems with fewer than six
supply voltages, and the open drain
RST
output of two or
more LTC2908s can be wired-OR together for monitoring
systems with more than six supply voltages. The common
reset output remains low until all six inputs have been in
compliance for 200ms.
The LTC2908 features a tight 1.5% threshold accuracy over
the entire operating temperature range and glitch immunity
to ensure reliable reset operation without false triggering.
The open-drain
RST
output state is guaranteed to be in the
correct state as long as V1 and/or V2 is 0.5V or greater.
The LTC2908 also features adjustable inputs with a nominal
threshold level at 0.5V. This product provides a precise,
space-conscious, micropower and general purpose solu-
tion for any kind of system requiring supply monitors.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. *Patent pending.
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Ultralow Voltage Reset: V
CC
= 0.5V Guaranteed*
Monitors Six Inputs Simultaneously:
5V, 3.3V, 2.5V, 1.8V, ADJ1, ADJ2 (LTC2908-A1)
3.3V, 2.5V, 1.8V, 1.5V, ADJ1, ADJ2 (LTC2908-B1)
2.5V, ADJ1, ADJ2, ADJ3, ADJ4, ADJ5 (LTC2908-C1)
Guaranteed Threshold Accuracy: ±1.5% of
Monitored Voltage Overtemperature
Internal V
CC
Auto Select
Power Supply Glitch Immunity
200ms Reset Time Delay
Active Low Open-Drain
RST
Output
Low Profile (1mm) 8-Lead SOT-23 (ThinSOT™) and
Plastic (3mm
×
2mm) DFN Packages
APPLICATIONS
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Network Servers
Wireless Base Stations
Optical Networking Systems
Multivoltage Systems
Desktop and Notebook Computers
TYPICAL APPLICATION
Six Supply Monitor with 5% Tolerance
(12V, 3.3V, 2.5V, 1.8V, 1.5V, 1.2V)
12V
DC/DC
DC/DC
DC/DC
DC/DC
DC/DC
3.3V
RST
Output Voltage vs V1
with 10k Pull-Up Resistor to V1
0.4
V3 = V4 = V
ADJ1
=
V
ADJ2
= V
ADJ3
=
V
ADJ4
= V
ADJ5
= GND
RST
OUTPUT VOLTAGE (V)
2.5V
1.8V
1.5V
1.2V
0.1μF 0.1μF
2.15M
100k
124k
100k
SYSTEM
0.3
V1 INPUT
0.2
V2 = GND
0.1
V2 = V1 (A1/B1)
0
0
0.2
0.4
V1 (V)
0.6
0.8
2908 TA01b
V1
V2 V3 V4
V
ADJ1
LTC2908-B1
GND
V
ADJ2
RST
2908 TA01a
2908fd
1
LTC2908
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
Terminal Voltages
V1, V2, V3, V4 .........................................– 0.3V to 7V
V
ADJ1
, V
ADJ2
, V
ADJ3
, ..................–0.3V to (V
CC
+ 0.6V)
V
ADJ4
, V
ADJ5
.............................–0.3V to (V
CC
+ 0.6V)
RST
.......................................................... –0.3V to 7V
Operating Temperature Range
LTC2908C ................................................ 0°C to 70°C
LTC2908I..............................................–40°C to 85°C
Storage Temperature Range
DFN Package......................................–65°C to 125°C
TSOT-23 Package...............................–65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
PIN CONFIGURATION
LTC2908CDDB-A1
LTC2908IDDB-A1
LTC2908CDDB-B1
LTC2908IDDB-B1
TOP VIEW
GND 1
RST
2
V4 3
V2 4
9
8 V
ADJ2
7 V3
6 V
ADJ1
5 V1
GND 1
RST
2
V
ADJ5
3
V1 4
9
LTC2908CDDB-C1
LTC2908IDDB-C1
LTC2908CTS8-A1
LTC2908ITS8-A1
LTC2908CTS8-B1
LTC2908ITS8-B1
LTC2908CTS8-C1
LTC2908ITS8-C1
TOP VIEW
8 V
ADJ4
7 V
ADJ3
6 V
ADJ2
5 V
ADJ1
V2 1
V4 2
RST
3
GND 4
TOP VIEW
8 V1
7 V
ADJ1
6 V3
5 V
ADJ2
V1 1
V
ADJ5
2
RST
3
GND 4
TOP VIEW
8 V
ADJ1
7 V
ADJ2
6 V
ADJ3
5 V
ADJ4
DDB8 PACKAGE
8-LEAD (3mm
×
2mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 76°C/W
EXPOSED PAD (PIN 9)
(PCB CONNECTION OPTIONAL)
DDB8 PACKAGE
8-LEAD (3mm
×
2mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 76°C/W
EXPOSED PAD (PIN 9)
(PCB CONNECTION OPTIONAL)
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 250°C/W
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C,
θ
JA
= 250°C/W
ORDER INFORMATION
Lead Free Finish
TAPE AND REEL (MINI)
TAPE AND REEL
PART MARKING* PACKAGE DESCRIPTION
LTC2908CDDB-A1#TRMPBF
LTC2908CDDB-A1#TRPBF
LBFD
8-LEAD (3mm
×
2mm) PLASTIC DFN
LTC2908IDDB-A1#TRMPBF
LTC2908IDDB-A1#TRPBF
LBFF
8-LEAD (3mm
×
2mm) PLASTIC DFN
LTC2908CDDB-B1#TRMPBF
LTC2908CDDB-B1#TRPBF
LBFG
8-LEAD (3mm
×
2mm) PLASTIC DFN
LTC2908IDDB-B1#TRMPBF
LTC2908IDDB-B1#TRPBF
LBFH
8-LEAD (3mm
×
2mm) PLASTIC DFN
LTC2908CDDB-C1#TRMPBF
LTC2908CDDB-C1#TRPBF
LCFV
8-LEAD (3mm
×
2mm) PLASTIC DFN
LTC2908IDDB-C1#TRMPBF
LTC2908IDDB-C1#TRPBF
LCFV
8-LEAD (3mm
×
2mm) PLASTIC DFN
LTC2908CTS8-A1#TRMPBF
LTC2908CTS8-A1#TRPBF
LTBFJ
8-LEAD PLASTIC TSOT-23
LTC2908ITS8-A1#TRMPBF
LTC2908ITS8-A1#TRPBF
LTBFK
8-LEAD PLASTIC TSOT-23
LTC2908CTS8-B1#TRMPBF
LTC2908CTS8-B1#TRPBF
LTBFM
8-LEAD PLASTIC TSOT-23
LTC2908ITS8-B1#TRMPBF
LTC2908ITS8-B1#TRPBF
LTBFN
8-LEAD PLASTIC TSOT-23
LTC2908CTS8-C1#TRMPBF
LTC2908CTS8-C1#TRPBF
LTCFT
8-LEAD PLASTIC TSOT-23
LTC2908ITS8-C1#TRMPBF
LTC2908ITS8-C1#TRPBF
LTCFT
8-LEAD PLASTIC TSOT-23
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
2908fd
2
LTC2908
ELECTRICAL CHARACTERISTICS
SYMBOL
V
RT50
V
RT33
V
RT25
V
RT18
V
RTADJ
PARAMETER
5V, 5% Reset Threshold
3.3V, 5% Reset Threshold
2.5V, 5% Reset Threshold
1.8V, 5% Reset Threshold
ADJ, 5% Reset Threshold
(LTC2908-A1) The
l
denotes specifications which apply over the full
operating temperature range, otherwise specifications are T
A
= 25°C, V
CC
= 5V unless otherwise noted. (Note 2)
CONDITIONS
V1 Input Threshold
V2 Input Threshold
V3 Input Threshold
V4 Input Threshold
V
ADJ1
, V
ADJ2
Input Threshold
l
l
l
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MIN
4.600
3.036
2.300
1.656
0.492
TYP
4.675
3.086
2.338
1.683
0.500
MAX
4.750
3.135
2.375
1.710
0.508
UNITS
V
V
V
V
V
(LTC2908-B1) The
l
denotes specifications which apply over the full operating temperature range, otherwise specifications are
T
A
= 25°C, V
CC
= 3.3V unless otherwise noted. (Note 2)
SYMBOL
V
RT33
V
RT25
V
RT18
V
RT15
V
RTADJ
PARAMETER
3.3V, 5% Reset Threshold
2.5V, 5% Reset Threshold
1.8V, 5% Reset Threshold
1.5V, 5% Reset Threshold
ADJ, 5% Reset Threshold
CONDITIONS
V1 Input Threshold
V2 Input Threshold
V3 Input Threshold
V4 Input Threshold
V
ADJ1
, V
ADJ2
Input Threshold
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l
l
l
l
MIN
3.036
2.300
1.656
1.380
0.492
TYP
3.086
2.338
1.683
1.403
0.500
MAX
3.135
2.375
1.720
1.425
0.508
UNITS
V
V
V
V
V
(LTC2908-C1) The
l
denotes specifications which apply over the full operating temperature range, otherwise specifications are
T
A
= 25°C, V
CC
= 2.5V unless otherwise noted. (Note 2)
SYMBOL
V
RT25
V
RTADJ
PARAMETER
2.5V, 5% Reset Threshold
ADJ, 5% Reset Threshold
CONDITIONS
V1 Input Threshold
V
ADJ1
, V
ADJ2
, V
ADJ3
, V
ADJ4
, V
ADJ5
,
Input Threshold
l
l
MIN
2.300
0.492
TYP
2.338
0.500
MAX
2.375
0.508
UNITS
V
V
The
l
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C. V
CC
= 5V
for the LT2908-A1, V
CC
= 3.3V for the LTC2908-B1or V
CC
= 2.5V for the LTC2908-C1, unless otherwise noted. (Notes 2, 3)
SYMBOL
V
CC
I
V1
PARAMETER
Internal Supply Voltage
V1 Input Current (Note 4)
CONDITIONS
RST
in Correct Logic State
V1 = 5.0V (LTC2908-A1)
V1 = 3.3V (LTC2908-B1)
V1 = 2.5V (LTC2908-C1)
V2 = 3.3V (LTC2908-A1)
V2 = 2.5V (LTC2908-B1)
V3 = 2.5V (LTC2908-A1)
V3 = 1.8V (LTC2908-B1)
V4 = 1.8V (LTC2908-A1)
V4 = 1.5V (LTC2908-B1)
V
ADJ1
= V
ADJ2
= V
ADJ3
= V
ADJ4
= V
ADJ5
=
0.55V
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l
l
l
l
l
l
l
l
l
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MIN
0.5
TYP
26
24
22
10
8
2
2
2
2
MAX
6
70
70
70
30
30
5
5
5
5
±15
UNITS
V
μA
μA
μA
μA
μA
μA
μA
μA
μA
nA
I
V2
I
V3
I
V4
I
VADJ
V2 Input Current (Note 4)
V3 Input Current
V4 Input Current
V
ADJ1
, V
ADJ2,
V
ADJ3,
V
ADJ4,
V
ADJ5
Input Current
2908fd
3
LTC2908
ELECTRICAL CHARACTERISTICS
The
l
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C. V
CC
= 5V
for the LT2908-A1, V
CC
= 3.3V for the LTC2908-B1 or V
CC
= 2.5V for the LTC2908-C1, unless otherwise noted. (Notes 2, 3)
SYMBOL
t
RST
t
UV
V
OH
PARAMETER
Reset Time-Out Period
V
X
Undervoltage Detect to
RST
Output Voltage High
RST
(Note 5)
V
X
Less Than Reset Threshold V
RTX
by
More Than 1%
I
RST
= –1μA, V
CC
= 5V (LTC2908-A1)
I
RST
= –1μA, V
CC
= 3.3V (LTC2908-B1)
I
RST
= –1μA, V
CC
= 2.5V (LTC2908-C1)
V
CC
= 0.5V, I
RST
= 5μA
V
CC
= 1.0V, I
RST
= 100μA
V
CC
= 3.0V, I
RST
= 2500μA
l
l
l
l
l
l
CONDITIONS
l
MIN
160
TYP
200
250
MAX
260
UNITS
ms
μs
V
V
V
V
CC
– 1.5
V
CC
– 1.0
V
CC
– 1.0
0.01
0.01
0.10
0.15
0.15
0.30
V
OL
Output Voltage Low
RST
V
V
V
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliabilty and lifetime.
Note 2:
The greater of V1, V2 is the internal supply voltage (V
CC
) for the
LTC2908-A1 and the LTC2908-B1. V1 is the internal supply voltage (V
CC
)
for the LTC2908-C1.
Note 3:
All currents into pins are positive; all voltages are referenced to
GND unless otherwise noted.
Note 4:
Under typical operating conditions, most of the quiescent cur-
rent is drawn from the V1 input. When V2 exceeds V1, V2 supplies most
of the quiescent current.
Note 5:
The output pin
RST
has an internal pull-up to V
CC
of typically
6μA. However, an external pull-up resistor may be used when a faster
rise time is required or for V
OH
voltages greater than V
CC
.
TYPICAL PERFORMANCE CHARACTERISTICS
Specifications are at T
A
= 25°C unless otherwise noted.
5V Threshold Voltage
vs Temperature
4.750
THRESHOLD VOLTAGE, V
RT50
(V)
3.3V Threshold Voltage
vs Temperature
3.135
THRESHOLD VOLTAGE, V
RT33
(V)
2.5V Threshold Voltage
vs Temperature
2.375
THRESHOLD VOLTAGE, V
RT25
(V)
4.725
4.700
4.675
4.650
4.625
4.600
–50
3.115
2.360
3.095
2.345
3.075
2.330
3.055
2.315
–25
50
25
0
TEMPERATURE (°C)
75
100
2908 G01
3.035
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
2908 G02
2.300
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
2908 G03
2908fd
4
LTC2908
TYPICAL PERFORMANCE CHARACTERISTICS
Specifications are at T
A
= 25°C unless otherwise noted.
1.8V Threshold Voltage
vs Temperature
1.710
THRESHOLD VOLTAGE, V
RT18
(V)
THRESHOLD VOLTAGE, V
RT15
(V)
1.425
THRESHOLD VOLTAGE, V
RTADJ
(V)
1.420
1.415
1.410
1.405
1.400
1.395
1.390
1.385
1.660
–50
–25
50
25
0
TEMPERATURE (°C)
75
100
2908 G04
1.5V Threshold Voltage
vs Temperature
0.5080
0.5060
0.5040
0.5020
0.5000
0.4980
0.4960
0.4940
ADJ Threshold Voltage
vs Temperature
1.700
1.690
1.680
1.670
1.380
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2908 G05
0.4920
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
2908 G06
I
V1
vs Temperature
33
V1 = 5.0V (A1)/V1 = 3.3V (B1)/V1 = 2.5V (C1)
31 V2 = 3.3V (A1)/V2 = 2.5V (B1)
V3 = 2.5V (A1)/V3 = 1.8V (B1)
29 V4 = 1.8V (A1)/V1 = 1.5V (B1)
V
ADJ1
= V
ADJ2
= V
ADJ3
=
V
ADJ4
=V
ADJ5
= 0.55V
27
A1
B1
25
23
C1
21
19
17
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2908 G07
I
V2
vs Temperature
V1 = 5.0V (A1)/V1 = 3.3V (B1)
13 V2 = 3.3V (A1)/V2 = 2.5V (B1)
V3 = 2.5V (A1)/V3 = 1.8V (B1)
12 V4 = 1.8V (A1)/V4 = 1.5V (B1)
11 V
ADJ1
= V
ADJ2
= 0.55V
I
V2
(μA)
A1
B1
I
V3
(μA)
10
9
8
7
6
5
4
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
2908 G08
I
V3
vs Temperature
V1 = 5.0V (A1)/V1 = 3.3V (B1)
2.1 V2 = 3.3V (A1)/V2 = 2.5V (B1)
V3 = 2.5V (A1)/V3 = 1.8V (B1)
2.0 V4 = 1.8V (A1)/V4 = 1.5V (B1)
V
ADJ1
= V
ADJ2
= 0.55V
1.9
1.8
1.7
1.6
1.5
1.4
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
2908 G09
14
2.2
I
V1
(μA)
I
V4
vs Temperature
TYPICAL TRANSIENT DURATION (μs)
V1 = 5.0V (A1)/V1 = 3.3V (B1)
2.1 V2 = 3.3V (A1)/V2 = 2.5V (B1)
V3 = 2.5V (A1)/V3 = 1.8V (B1)
2.0 V4 = 1.8V (A1)/V4 = 1.5V (B1)
V
ADJ1
= V
ADJ2
= 0.55V
1.9
I
V4
(μA)
1.8
1.7
1.6
1.5
1.4
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
2908 G10
Typical Transient Duration
vs Comparator Overdrive
700
600
500
400
300
200
100
0
0.1
1
10
100
COMPARATOR OVERDRIVE VOLTAGE (% OF V
RTX
)
2908 G11
Reset Time-Out Period (t
RST
)
vs Temperature
T
A
= 25°C
RESET TIME-OUT PERIOD, t
RST
(ms)
250
240
230
220
210
200
190
180
170
160
150
–50
–25
50
25
TEMPERATURE (°C)
0
75
100
2908 G12
2.2
RESET OCCURS
ABOVE CURVE
2908fd
5
51单片机
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