LMx35, LMx35A Precision Temperature Sensors
- SNIS160E May 1999 – February 2015 LM135 , LM135A , LM235 , LM235A , LM335 , LM335A
  
  PRODUCTION DATA.

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DATA SHEET

LMx35, LMx35A Precision Temperature Sensors

1 Features

Directly Calibrated to the Kelvin Temperature Scale
1°C Initial Accuracy Available
Operates from 400 μA to 5 mA
Less than 1-Ω Dynamic Impedance
Easily Calibrated
Wide Operating Temperature Range
200°C Overrange
Low Cost

2 Applications

Power Supplies
Battery Management
HVAC
Appliances

3 Description

The LM135 series are precision, easily-calibrated, integrated circuit temperature sensors. Operating as a 2-terminal zener, the LM135 has a breakdown voltage directly proportional to absolute temperature at 10 mV/°K. With less than 1-Ω dynamic impedance, the device operates over a current range of 400 μA to 5 mA with virtually no change in performance. When calibrated at 25°C, the LM135 has typically less than 1°C error over a 100°C temperature range. Unlike other sensors, the LM135 has a linear output.

Applications for the LM135 include almost any type of temperature sensing over a −55°C to 150°C temperature range. The low impedance and linear output make interfacing to readout or control circuitry are especially easy.

The LM135 operates over a −55°C to 150°C temperature range while the LM235 operates over a −40°C to 125°C temperature range. The LM335 operates from −40°C to 100°C. The LMx35 devices are available packaged in hermetic TO transistor packages while the LM335 is also available in plastic TO-92 packages.

Device Information⁽¹⁾

PART NUMBER	PACKAGE	BODY SIZE (NOM)
LM135	TO-46 (3)	4.699 mm × 4.699 mm
LM135A	TO-46 (3)	4.699 mm × 4.699 mm
LM235	TO-92 (3)	4.30 mm × 4.30 mm
LM235A	TO-92 (3)	4.30 mm × 4.30 mm
LM335	SOIC (8)	4.90 mm × 3.91 mm
LM335A	SOIC (8)	4.90 mm × 3.91 mm

For all available packages, see the orderable addendum at the end of the datasheet.

Basic Temperature Sensor Simplified Schematic

Calibrated Sensor

4 Revision History

Changes from D Revision (March 2013) to E Revision

Added Pin Configuration and Functions section, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information sectionGo

Changes from C Revision (November 2012) to D Revision

Changed layout of National Data Sheet to TI formatGo

5 Pin Configuration and Functions

TO-46 (NDV)

3 Pins

Bottom View

TO-92 (LP)

3 Pins

Bottom View

SOIC (D)

8 Pins

Top View

Pin Functions

PIN				I/O	DESCRIPTION
NAME	TO-46	TO-92	SO8	I/O	DESCRIPTION
N.C.	—	—	1	—	No Connection
	—	—	2
	—	—	3
–	—	—	4	O	Negative output
ADJ	—	—	5	I	Calibration adjust pin
N.C.	—	—	6	—	No Connection
N.C.	—	—	7	—	No Connection
+	—	—	8	I	Positive input

6 Specifications

6.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)⁽¹⁾⁽³⁾⁽²⁾⁽⁴⁾

		MIN	MAX	UNIT
Reverse Current			15	mA
Forward Current			10	mA
Storage temperature, T_stg	8-Pin SOIC Package	−65	150	°C
Storage temperature, T_stg	TO / TO-92 Package	−60	150	°C

(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

(2) If Military/Aerospace specified devices are required, please contact the TI Sales Office/Distributors for availability and specifications.

(3) Refer to RETS135H for military specifications.

(4) Soldering process must comply with the Reflow Temperature Profile specifications. Refer to http://www.ti.com/packaging.

6.2 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)

			MIN	NOM	MAX	UNIT
Specified Temperature	LM135, LM135A	Continuous (T_MIN ≤ T_A ≤ T_MAX)	−55		150	°C
	LM135, LM135A	Intermittent ⁽¹⁾	150		200	°C
	LM235, LM235A	Continuous (T_MIN ≤ T_A ≤ T_MAX)	−40		125	°C
	LM235, LM235A	Intermittent ⁽¹⁾	125		150	°C
	LM335, LM335A	Continuous (T_MIN ≤ T_A ≤ T_MAX)	−40		100	°C
	LM335, LM335A	Intermittent ⁽¹⁾	100		125	°C
Forward Current			0.4	1	5	mA

(1) Continuous operation at these temperatures for 5,000 hours for LP package may decrease life expectancy of the device.

6.3 Thermal Information

THERMAL METRIC⁽¹⁾		LM335 / LM335A	LM235 / LM235A	LM135 / LM135A	UNIT
		SOIC (D)	TO-92 (LP)	TO-46 (NDV)
		8 PINS	3 PINS	3 PINS
R_θJA	Junction-to-ambient thermal resistance	165	202	400	°C/W
R_θJC	Junction-to-case thermal resistance	—	170	—	°C/W

(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.

6.4 Temperature Accuracy: LM135/LM235, LM135A/LM235A⁽¹⁾

PARAMETER		TEST CONDITIONS	LM135A/LM235A			LM135/LM235			UNIT
PARAMETER		TEST CONDITIONS	MIN	TYP	MAX	MIN	TYP	MAX	UNIT
Operating Output Voltage		T_C = 25°C, I_R = 1 mA	2.97	2.98	2.99	2.95	2.98	3.01	V
Uncalibrated Temperature Error		T_C = 25°C, I_R = 1 mA		0.5	1		1	3	°C
Uncalibrated Temperature Error		T_MIN ≤ T_C ≤ T_MAX, I_R = 1 mA		1.3	2.7		2	5	°C
Temperature Error with 25°C		T_MIN ≤ T_C ≤ T_MAX, I_R = 1 mA		0.3	1		0.5	1.5	°C
Calibration	Calibrated Error at Extended	T_C = T_MAX (Intermittent)		2			2		°C
Temperature	Non-Linearity	I_R = 1 mA		0.3	0.5		0.3	1	°C

6.5 Temperature Accuracy: LM335, LM335A⁽¹⁾

PARAMETER		TEST CONDITIONS	LM335A			LM335			UNIT
PARAMETER		TEST CONDITIONS	MIN	TYP	MAX	MIN	TYP	MAX	UNIT
Operating Output Voltage		T_C = 25°C, I_R = 1 mA	2.95	2.98	3.01	2.92	2.98	3.04	V
Uncalibrated Temperature Error		T_C = 25°C, I_R = 1 mA		1	3		2	6	°C
Uncalibrated Temperature Error		T_MIN ≤ T_C ≤ T_MAX, I_R = 1 mA		2	5		4	9	°C
Temperature Error with 25°C		T_MIN ≤ T_C ≤ T_MAX, I_R = 1 mA		0.5	1		1	2	°C
Calibration	Calibrated Error at Extended	T_C = T_MAX (Intermittent)		2			2		°C
Temperature	Non-Linearity	I_R = 1 mA		0.3	1.5		0.3	1.5	°C

6.6 Electrical Characteristics

See ⁽¹⁾.

PARAMETER	TEST CONDITIONS	LM135/LM235/LM135A/LM235A			LM335/LM335A			UNIT
PARAMETER	TEST CONDITIONS	MIN	TYP	MAX	MIN	TYP	MAX	UNIT
Operating Output Voltage Change with Current	400 μA ≤ I_R ≤ 5 mA, At Constant Temperature		2.5	10		3	14	mV
Dynamic Impedance	I_R = 1 mA		0.5			0.6		Ω
Output Voltage Temperature Coefficient			10			10		mV/°C
Time Constant	Still Air		80			80		sec
	100 ft/Min Air		10			10		sec
	Stirred Oil		1			1		sec
Time Stability	T_C = 125°C		0.2			0.2		°C/khr

(1) Accuracy measurements are made in a well-stirred oil bath. For other conditions, self heating must be considered.

6.7 Typical Characteristics

Figure 1. Reverse Voltage Change

Figure 3. Reverse Characteristics

Figure 5. Dynamic Impedance

Figure 7. Thermal Resistance Junction To Air

Figure 9. Thermal Response In Still Air

Figure 11. Forward Characteristics

Figure 2. Calibrated Error

Figure 4. Response Time

Figure 6. Noise Voltage

Figure 8. Thermal Time Constant

Figure 10. Thermal Response In Stirred Oil Bath

7 Detailed Description

7.1 Overview

The LM135 operates over a −55°C to 150°C temperature range while the LM235 operates over a −40°C to 125°C temperature range. The LM335 operates from −40°C to 100°C.

Operating as a 2-terminal zener, the LM135 has a breakdown voltage directly proportional to absolute temperature at 10 mV/°K. With less than 1-Ω dynamic impedance, the device operates over a current range of 400 μA to 5 mA with virtually no change in performance. When calibrated at 25°C, the LM135 has typically less than 1°C error over a 100°C temperature range. Unlike other sensors, the LM135 has a linear output.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Temperature Calibration Using ADJ Pin

Included on the LM135 chip is an easy method of calibrating the device for higher accuracies. A pot connected across the LM135 with the arm tied to the adjustment terminal (as shown in Figure 12) allows a 1-point calibration of the sensor that corrects for inaccuracy over the full temperature range.

This single point calibration works because the output of the LM135 is proportional to absolute temperature with the extrapolated output of sensor going to 0-V output at 0 K (−273.15°C). Errors in output voltage versus temperature are only slope (or scale factor) errors so a slope calibration at one temperature corrects at all temperatures.

The output of the device (calibrated or uncalibrated) can be expressed as:

Equation 1.

where

T is the unknown temperature in degrees Kelvin
T_o is a reference temperature in degrees Kelvin

By calibrating the output to read correctly at one temperature the output at all temperatures is correct. Nominally the output is calibrated at 10 mV/K.

Calibrate for 2.982V at 25°C

Figure 12. Calibrated Sensor

7.4 Device Functional Modes

The LM135 has two functional modes calibrated and uncalibrated. For optimum accuracy, a one point calibration is recommended. For more information on calibration, see Temperature Calibration Using ADJ Pin.

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

To insure good sensing accuracy, several precautions must be taken. Like any temperature-sensing device, self-heating can reduce accuracy. The LM135 should be operated at the lowest current suitable for the application. Sufficient current, of course, must be available to drive both the sensor and the calibration pot at the maximum operating temperature as well as any external loads.

If the sensor is used in an ambient where the thermal resistance is constant, self-heating errors can be calibrated out. This is possible if the device is run with a temperature-stable current. Heating will then be proportional to zener voltage and therefore temperature. This makes the self-heating error proportional to absolute temperature the same as scale factor errors.

8.2 Typical Application

Figure 13. Basic Temperature Sensor

8.2.1 Design Requirements

Table 1. Design Parameters

PARAMETER	EXAMPLE VALUE
Accuracy at 25°C	±1°C
Accuracy from –55 °C to 150 °C	±2.7°C
Forward Current	1 mA
Temperature Slope	10m V/K

8.2.2 Detailed Design Procedure

For optimum accuracy, R1 is picked such that 1 mA flows through the sensor. Additional error can be introduced by varying load currents or varying supply voltage. The influence of these currents on the minimum and maximum reverse current flowing through the LM135 should be calculated and be maintained in the range of 0.4 mA to 5 mA. Minimizing the current variation through the LM135 will provide for the best accuracy. The Operating Output Voltage Change with Current specification can be used to calculate the additional error which could be up to 1 K maximum from the LM135A, for example.

8.2.3 Application Curve

Figure 14. Reverse Characteristics

8.3 System Examples

Figure 15. Wide Operating Supply

Wire length for 1°C error due to wire drop

Figure 17. Average Temperature Sensing

Figure 19. Simple Temperature Controller

Adjust R2 for 2.554V across LM336.
Adjust R1 for correct output.

Figure 21. Ground Referred Fahrenheit Thermometer

To calibrate adjust R2 for 2.554V across LM336.
Adjust R1 for correct output.

Figure 23. Fahrenheit Thermometer

Figure 16. Minimum Temperature Sensing

Figure 18. Isolated Temperature Sensor

Figure 20. Simple Temperature Control

Adjust for 2.7315V at output of LM308

Figure 22. Centigrade Thermometer

8.3.1 Thermocouple Cold Junction Compensation

Compensation for Grounded Thermocouple

Select R3 for proper thermocouple type

Figure 24. Thermocouple Cold Junction Compensation

THERMO-COUPLE	R3 (±1%)	SEEBECK COEFFICIENT
J	377 Ω	52.3 μV/°C
T	308 Ω	42.8 μV/°C
K	293 Ω	40.8 μV/°C
S	45.8 Ω	6.4 μV/°C
Adjustments: Compensates for both sensor and resistor tolerances Short LM329B Adjust R1 for Seebeck Coefficient times ambient temperature (in degrees K) across R3. Short LM335 and adjust R2 for voltage across R3 corresponding to thermocouple type. J 14.32 mV K 11.17 mV T 11.79 mV S 1.768 mV

THERMO-COUPLE	R3	R4	SEEBECK COEFFICIENT
J	1.05K	385Ω	52.3 μV/°C
T	856Ω	315Ω	42.8 μV/°C
K	816Ω	300Ω	40.8 μV/°C
S	128Ω	46.3Ω	6.4 μV/°C
Adjustments: Adjust R1 for the voltage across R3 equal to the Seebeck Coefficient times ambient temperature in degrees Kelvin. Adjust R2 for voltage across R4 corresponding to thermocouple.
J	14.32 mV
T	11.79 mV
K	11.17 mV
S	1.768 mV

Select R3 and R4 for thermocouple type

Figure 25. Single Power Supply Cold Junction Compensation

Figure 27. Differential Temperature Sensor

Adjust D1 to 50 mV greater V_Z than D2.
Charge terminates on 5°C temperature rise.
Couple D2 to battery.

Figure 29. Fast Charger For Nickel-Cadmium Batteries

Figure 31. Ground Referred Centigrade Thermometer

Terminate thermocouple reference junction in close proximity to LM335.
Adjustments:
1. Apply signal in place of thermocouple and adjust R3 for a gain of 245.7.
2. Short non-inverting input of LM308A and output of LM329B to ground.
3. Adjust R1 so that V_OUT = 2.982V @ 25°C.
4. Remove short across LM329B and adjust R2 so that V_OUT = 246 mV @ 25°C.
5. Remove short across thermocouple.

Figure 26. Centigrade Calibrated Thermocouple Thermometer

Figure 28. Differential Temperature Sensor

Adjust for zero with sensor at 0°C and 10T pot set at 0°C
Adjust for zero output with 10T pot set at 100°C and sensor at 100°C
Output reads difference between temperature and dial setting of 10T pot

Figure 30. Variable Offset Thermometer

*Self heating is used to detect air flow

Figure 32. Air Flow Detector