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PDF LTC2983 Data sheet ( Hoja de datos )
| Número de pieza | LTC2983 | |
| Descripción | Multi-Sensor High Accuracy Digital Temperature Measurement System | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
nn Directly Digitize RTDs, Thermocouples, Thermistors
and Diodes
nn Single 2.85V to 5.25V Supply
nn Results Reported in °C or °F
nn 20 Flexible Inputs Allow Interchanging Sensors
nn Automatic Thermocouple Cold Junction Compensation
nn Built-In Standard and User-Programmable Coefficients
for Thermocouples, RTDs and Thermistors
nn Configurable 2-, 3- or 4-Wire RTD Configurations
nn Measures Negative Thermocouple Voltages
nn Automatic Burn Out, Short-Circuit and Fault Detection
nn Buffered Inputs Allow External Protection
nn Simultaneous 50Hz/60Hz Rejection
nn Includes 15ppm/°C (Max) Reference (I-Grade)
APPLICATIONS
nn Direct Thermocouple Measurements
nn Direct RTD Measurements
nn Direct Thermistor Measurements
nn Custom Sensor Applications
LTC2983
Multi-Sensor High Accuracy
Digital Temperature
Measurement System
DESCRIPTION
The LTC®2983 measures a wide variety of temperature
sensors and digitally outputs the result, in °C or °F, with
0.1°C accuracy and 0.001°C resolution. The LTC2983 can
measure the temperature of virtually all standard (type B,
E, J, K, N, S, R, T) or custom thermocouples, automatically
compensate for cold junction temperatures and linearize
the results. The device can also measure temperature with
standard 2-, 3- or 4-wire RTDs, thermistors and diodes. It
has 20 reconfigurable analog inputs enabling many sen-
sor connections and configuration options. The LTC2983
includes excitation current sources and fault detection
circuitry appropriate for each type of temperature sensor.
The LTC2983 allows direct interfacing to ground referenced
sensors without the need for level shifters, negative supply
voltages, or external amplifiers. All signals are buffered and
simultaneously digitized with three high accuracy, 24-bit ∆∑
ADCs, driven by an internal 15ppm/°C (maximum) reference.
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.
Patents Pending
TYPICAL APPLICATION
Thermocouple Measurement with Automatic Cold Junction Compensation
2.85V TO 5.25V
1k
0.1µF
1k
24-BIT
∆∑ ADC
LTC2983
RSENSE
2k
43
PT-100
RTD
2
1
24-BIT
∆∑ ADC
LINEARIZATION/
FAULT DETECTION
SPI
INTERFACE
°C/°F
24-BIT
∆∑ ADC
VREF (10ppm/°C)
2983 TA01a
For more information www.linear.com/LTC2983
Typical Temperature Error Contribution
0.5
0.4
0.3 THERMISTOR
0.2 THERMOCOUPLE
0.1
0
–0.1
–0.2 3904 DIODE
–0.3 RTD
–0.4
–0.5
–200 0
200 400 600 800 1000 1200 1400
TEMPERATURE (°C)
2983 TA01b
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1 page  
LTC2983
DIGITAL INPUTS AND DIGITAL OUTPUTS The l denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at TA = 25°C.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX
UNITS
External SCK Frequency Range
l0
2 MHz
External SCK LOW Period
l 250
ns
External SCK HIGH Period
l 250
ns
t1 CS↓ to SDO Valid
t2 CS↑ to SDO Hi-Z
t3 CS↓ to SCK↑
t4 SCK↓ to SDO Valid
t5 SDO Hold After SCK↓
t6 SDI Setup Before SCK↑
t7 SDI HOLD After SCK↑
High Level Input Voltage
Low Level Input Voltage
CS, SDI, SCK, RESET
CS, SDI, SCK, RESET
l0
l0
l 100
l
l 10
l 100
l 100
l VDD – 0.5
l
200 ns
200 ns
ns
225 ns
ns
ns
ns
V
0.5 V
Digital Input Current
CS, SDI, SCK, RESET
l –10
10 µA
Digital Input Capacitance
CS, SDI, SCK, RESET
10 pF
LOW Level Output Voltage (SDO, INTERRUPT)
High Level Output Voltage (SDO, INTERRUPT)
Hi-Z Output Leakage (SDO)
IO = –800µA
IO = 1.6mA
l
l VDD – 0.5
l –10
0.4 V
V
10 µA
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 voltage values are with respect to GND.
Note 3: Full scale ADC error. Measurements do not include reference error.
Note 4: Guaranteed by design, not subject to test.
Note 5: The input referred noise includes the contribution of internal
calibration operations.
Note 6: MUX configuration delay = default 1ms
Note 7: Global configuration set to 60Hz rejection.
Note 8: Global configuration set to 50Hz rejection.
Note 9: Global configuration default 50Hz/60Hz rejection.
Note 10: The exact value of VREF is stored in the LTC2983 and used
for all measurement calculations. Temperature coefficient is measured
by dividing the maximum change in output voltage by the specified
temperature range.
Note 11: A nalog power-up. Command status register inaccessible during
this time.
Note 12: D igital initialization. Begins at the conclusion of Analog Power-
Up. Command status register is 0 × 80 at the beginning of digital
initialization and 0 × 40 at the conclusion.
Note 13: Long-term stability typically has a logarithmic characteristic
and therefore, changes after 1000 hours tend to be much smaller than
before that time. Total drift in the second thousand hours is normally less
than one third that of the first thousand hours with a continuing trend
toward reduced drift with time. Long-term stability will also be affected by
differential stresses between the IC and the board material created during
board assembly.
Note 14: Hysteresis in output voltage is created by package stress
that differs depending on whether the IC was previously at a higher or
lower temperature. Output voltage is always measured at 25°C, but
the IC is cycled to the hot or cold temperature limit before successive
measurements. Hysteresis measures the maximum output change for the
averages of three hot or cold temperature cycles. For instruments that
are stored at well controlled temperatures (within 20 or 30 degrees of
operational temperature), it is usually not a dominant error source. Typical
hysteresis is the worst-case of 25°C to cold to 25°C or 25°C to hot to
25°C, preconditioned by one thermal cycle.
Note 15: Differential Input Range is ±VREF/2.
Note 16:RTD and thermistor measurements are made ratiometrically. As a
result current source excitation variation does not affect absolute accuracy.
Choose an excitation current such that largest sensor or RSENSE resistance
value, when driven by the nominal excitation current, will drop 1V or less.
The extended ADC input range will accommodate variation in excitation
current and the ratiometric calculation will negate the absolute value of the
excitation current.
Note 17: Do not apply voltage or current sources to these pins. They must
be connected to capacitive loads only, otherwise permanent damage may
occur.
Note 18: Input leakage measured with VIN = –10mV and VIN = 2.5V.
For more information www.linear.com/LTC2983
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TEST CIRCUITS
SDO
1.69k
CLOAD = 20pF
Hi-Z TO VOH
VOL TO VOH
VOH TO Hi-Z
VDD
1.69k
SDO
CLOAD = 20pF
Hi-Z TO VOL
VOH TO VOL
VOL TO Hi-Z
2983 TC01
LTC2983
TIMING DIAGRAM
CS
SDO
t1
SCK
SDI
t3
SPI Timing Diagram
t4
t7
t6
t5 t2
2983 TD01
For more information www.linear.com/LTC2983
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11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTC2983.PDF ] | |
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