LTC2997
Remote/Internal
Temperature Sensor
FEATURES
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DESCRIPTION
The LTC
®
2997 is a high-accuracy analog output temperature
sensor. It converts the temperature of an external sensor or
its own temperature to an analog voltage output. A built-in
algorithm eliminates errors due to series resistance be-
tween the LTC2997 and the sensor diode.
The LTC2997 gives accurate results with low-cost diode-
connected NPN or PNP transistors or with integrated
temperature transistors on microprocessors or FPGAs.
Tying pin D
+
to V
CC
configures the LTC2997 to measure
its internal temperature.
The LTC2997 provides an additional 1.8V reference voltage
output which can be used as an ADC reference input or
for generating temperature threshold voltages to compare
against the V
PTAT
output.
The LTC2997 provides a precise and versatile micropower
solution for accurate temperature sensing.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Converts Remote Sensor or Internal Diode
Temperature to Analog Voltage
±1°C Remote Temperature Accuracy
±1.5°C Internal Temperature Accuracy
Built-In Series Resistance Cancellation
2.5V to 5.5V Supply Voltage
1.8V Reference Voltage Output
3.5ms V
PTAT
Update Time
4mV/°K Output Gain
170μA Quiescent Current
Available in 6-Pin 2mm × 3mm DFN Package
APPLICATIONS
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Temperature Measurement
Remote Temperature Measurement
Environmental Monitoring
System Thermal Control
Desktop and Notebook Computers
Network Servers
TYPICAL APPLICATION
Single Remote Temperature Sensor
2.5V TO 5.5V
0.1μF
1.6
V
PTAT
vs Remote Sensor Temperature
1.8
MMBT 3904
D
+
470pF
D
–
VCC
VREF
LTC2997
VPTAT
1.8V
V
PTAT
(V)
1.4
4mV/K
1.2
GND
2997 TA01a
1.0
0.8
25 50 75 100 125 150
–50 –25 0
REMOTE SENSOR TEMPERATURE (°C)
2997 TA01b
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LTC2997
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
Terminal Voltages
V
CC
........................................................... –0.3V to 6V
D
+
, D
–
, V
PTAT
, V
REF
......................–0.3V to V
CC
+ 0.3V
Operating Ambient Temperature Range
LTC2997C ................................................ 0°C to 70°C
LTC2997I .............................................–40°C to 85°C
LTC2997H .......................................... –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
PIN CONFIGURATION
TOP VIEW
D
+
1
D
–
2
V
PTAT
3
7
6 V
REF
5 GND
4 V
CC
DCB PACKAGE
6-LEAD (2mm 3mm) PLASTIC DFN
T
JMAX
= 150°C,
θ
JA
= 64°C/W
EXPOSED PAD PCB GROUND CONNECTION OPTIONAL
ORDER INFORMATION
Lead Free Finish
TAPE AND REEL (MINI)
LTC2997CDCB#TRMPBF
LTC2997IDCB#TRMPBF
TAPE AND REEL
LTC2997CDCB#TRPBF
LTC2997IDCB#TRPBF
PART MARKING*
LFQZ
LFQZ
PACKAGE DESCRIPTION
6-Lead (2mm × 3mm) Plastic DFN
6-Lead (2mm × 3mm) Plastic DFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
LTC2997HDCB#TRMPBF
LTC2997HDCB#TRPBF
LFQZ
6-Lead (2mm × 3mm) Plastic DFN
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/
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LTC2997
ELECTRICAL CHARACTERISTICS
SYMBOL
V
CC
UVLO
I
CC
V
REF
PARAMETER
Supply Voltage
Supply Undervoltage Lockout Threshold
Average Supply Current
Reference Voltage
LTC2997
LTC2997C
LTC2997I
LTC2997H
I
LOAD
= ±200μA; V
CC
= 3.3V
(Note 3)
η
= 1.004 (Note 4)
I
LOAD
= ±200μA; V
CC
= 3.3V (Note 7)
LTC2997C, LTC2997I
LTC2997H
0°C to 100°C (Notes 5, 7)
–40°C to 0°C (Notes 5, 7)
100°C to 125°C (Notes 5, 7)
2.5V ≤ V
CC
≤ 5.5V
R
SERIES
= 100Ω
(Note 6)
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
CC
= 3.3V, unless otherwise noted.
CONDITIONS
l
MIN
2.5
1.7
120
1.797
1.793
1.790
1.787
–8
l
l
l
TYP
3.3
1.9
170
1.8
1.8
1.8
1.8
MAX
5.5
2.1
250
1.803
1.804
1.807
1.808
±1.5
–192
UNITS
V
V
μA
V
V
V
V
mV
μA
mV
ms
mV/°K
mV
°C
°C
°C
°C
°C
°C/V
°C
°C RMS
°C/√Hz
V
CC
Falling
Temperature Monitoring
l
l
l
l
V
REF
Load Regulation Error
Remote Sense Current
Diode Select Threshold
T
UPDATE
K
T
T
INT
T
RMT
Temperature Update Interval
V
PTAT
Slope
V
PTAT
Load Regulation
Internal Temperature Error
Remote Temperature Error,
η
= 1.004
V
CC
– 600 V
CC
– 300 V
CC
– 100
3.5
4
±1.5
±0.5
±0.25
±0.25
±0.1
±0.25
0.25
0.015
±1.5
±2
±1
±1.5
±1.5
±1
±1
5
T
VCC
T
RS
Temperature Error vs Supply
Series Resistance Cancellation Error
Temperature Noise
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
reliability and lifetime.
Note 2:
All currents into pins are positive; all voltages are referenced to
GND unless otherwise noted.
Note 3:
If voltage on pin D
+
exceeds the diode select threshold the
LTC2997 uses the internal diode sensor.
Note 4:
η
= ideality factor of remote diode
Note 5:
Remote diode temperature.
Note 6:
Guaranteed by design and not subject to test.
Note 7:
Guaranteed by design and test correlation.
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LTC2997
TYPICAL PERFORMANCE CHARACTERISTICS
Temperature Error with LTC2997
at Same Temperature as Remote
Diode
3
2
T
RMT
ERROR (°C)
T
RMT
ERROR (°C)
1
0
–1
–2
–3
–50 –25
3
2
T
INT
ERROR (°C)
0
25
50 75
T
A
(°C)
100 125 150
2997 G02
T
A
= 25°C, V
CC
= 3.3V unless otherwise noted.
Internal Temperature Error vs
T
A
, T
INT
3
2
1
0
–1
–2
–3
–50 –25
Remote Temperature Error vs
T
A
with Remote Diode at 25°C
1
0
–1
–2
–3
–50 –25
0
25
50 75
T
A
(°C)
100 125 150
2997 G01
0
25
50 75
T
A
(°C)
100 125 150
2997 G03
Temperature Error vs
V
CC
- Remote/Internal, T
VCC
0.4
0.2
0
ERROR (°C)
Remote Temperature Error vs
Series Resistance, T
RS
1.5
1.0
0.4
0.8
Remote Temperature Error vs
C
DECOUPLE
(Between D
+
and D
–
)
0.5
ERROR (°C)
0
–0.5
–0.4
ERROR (°C)
0
–0.2
–0.4
–0.6
–0.8
–1.0
1
2
3
V
CC
(V)
2997 G04
–1.0
–1.5
0
200
400
600
800
SERIES RESISTOR (Ω)
1000
2997 G05
4
5
6
–0.8
0
3
4
1
2
DECOUPLE CAPACITOR (nF)
5
2997 G06
V
PTAT
Noise vs Averaging Time
0.30
0.25
V
PTAT
NOISE (°C RMS)
0.20
UVLO (V)
0.15
0.10
0.05
0
0.01
2.4
2.2
2.0
1.8
1.6
1.4
1.2
UVLO vs Temperature
V
CC
Rising, Falling
V
CC
RISING
V
CC
FALLING
1.810
Buffered Reference Voltage
vs Temperature, V
REF
1.805
V
RFE
(V)
1.800
1.795
10
1
0.1
AVERAGING TIME (ms)
100
2997 G07
1.0
–50 –25
0
25
50 75 100 125 150 175
T
A
(°C)
2997 G08
1.790
–50 –25
0
25
50 75
T
A
(°C)
100 125 150
2997 G09
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LTC2997
TYPICAL PERFORMANCE CHARACTERISTICS
Load Regulation of V
REF
–
Voltage vs Current
1.820
V
CC
= 2.5V
V
CC
= 3.5V
V
CC
= 4.5V
V
CC
= 5.5V
V
PTAT
(V)
1.28
1.27
1.26
T
A
= 25°C, V
CC
= 3.3V unless otherwise noted.
Load Regulation of V
PTAT
–
Voltage vs Current
V
CC
= 2.5V
V
CC
= 3.5V
V
CC
= 4.5V
V
CC
= 5.5V
Supply Current vs Temperature
200
190
SUPPLY CURRENT (μA)
1.810
V
REF
(V)
180
1.800
1.25
1.24
170
1.790
1.23
160
1.780
–4
0
–2
2
LOAD CURRENT (mA)
4
2997 G10
1.22
–4
2
–2
0
LOAD CURRENT (mA)
4
2997 G11
150
–50 –25
0
25
50 75
T
A
(°C)
100 125 150
2997 G12
LTC2997 Internal Sensor
Thermal Step Response
125
100
75
V
PTAT
(°C)
50
25
0
ICE
–25 WATER
–50
0
1
AIR
BOILING
WATER
3
2
TIME (s)
4
5
2997 G13
Remote Temperature Error vs
Leakage Current at D
+
with
Remote Diode at 25°C, T
RMT
6
4
T
RMT
ERROR (°C)
2
0
–2
–4
–6
–200
ABSOLUTE TEMPERATURE ERROR (°C)
10
Single Wire Remote Temperature
Error vs Potential Difference Between
Remote and Local Ground (VAC)
VAC = 50mV
P-P
1
0.1
–100
0
I
LEAKAGE
(nA)
100
200
2997 G14
0.01
0.1
1
100
10
FREQUENCY (kHz)
1000
2997 G15
LTC2997 CONNECTED VIA 5 INCH
30AWG WRAPPING WIRES
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