SNIS118G July   1999  – January 2017 LM50 , LM50-Q1


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics: LM50B
    6. 6.6 Electrical Characteristics: LM50C and LM50-Q1
    7. 6.7 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 LM50 and LM50-Q1 Transfer Function
    4. 7.4 Device Functional Modes
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Full-Range Centigrade Temperature Sensor
        1. Design Requirements
        2. Detailed Design Procedure
          1. Capacitive Loads
        3. Application Curve
    3. 8.3 System Examples
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Considerations
  11. 11Device and Documentation Support
    1. 11.1 Related Links
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Application and Implementation


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.

Application Information

The LM50 and LM50-Q1 have a wide supply range and a 10 mV/°C output slope with a 500-mV DC offset. Therefore, it can be easily applied in many temperature-sensing applications where a single supply is required for positive and negative temperatures.

Typical Application

Full-Range Centigrade Temperature Sensor

LM50 LM50-Q1 full_range_centigrade_temp_sensor_snis118.gif Figure 12. Full-Range Centigrade Temperature Sensor Diagram(–40°C to 125°C)

Design Requirements

For this design example, use the parameters listed in Table 1 as the input parameters.

Table 1. Design Parameters

Power supply voltage ±3°C (maximum)
Output impedance ±4°C (maximum)
Accuracy at 25°C 10 mV/°C
Accuracy over –40°C to 125°C 4.5 V to 10 V
Temperature slope 4 kΩ (maximum)

Detailed Design Procedure

The LM50 and LM50-Q1 are simple temperature sensors that provides an analog output. Therefore design requirements related to layout are more important than other requirements. See Layout for more information.

Capacitive Loads

The LM50 and LM50-Q1 handle capacitive loading very well. Without any special precautions, the LM50 and LM50-Q1 can drive any capacitive load. The device has a nominal 2-kΩ output impedance (shown in Functional Block Diagram). The temperature coefficient of the output resistors is around 1300 ppm/°C. Taking into account this temperature coefficient and the initial tolerance of the resistors the output impedance of the device will not exceed 4 kΩ. In an extremely noisy environment it may be necessary to add some filtering to minimize noise pickup. TI recommends adding a 0.1-µF capacitor between +VS and GND to bypass the power supply voltage, as shown in Figure 14. It may also be necessary to add a capacitor from VOUT to ground. A 1-µF output capacitor with the 4-kΩ output impedance will form a 40-Hz low-pass filter. Since the thermal time constant of the LM50 and LM50-Q1 is much slower than the 25-ms time constant formed by the RC, the overall response time of the device will not be significantly affected. For much larger capacitors this additional time lag will increase the overall response time of the LM50 and LM50-Q1.

LM50 LM50-Q1 01203007.gif Figure 13. LM50 and LM50-Q1 No Decoupling Required
for Capacitive Load
LM50 LM50-Q1 01203008.gif Figure 14. LM50C and LM50-Q1 with Filter for Noisy Environment

Application Curve

LM50 LM50-Q1 C001_SNIS177.png Figure 15. Output Transfer Function

System Examples

Figure 16 to Figure 18 show application circuit examples using the LM50 or LM50-Q1 devices. Customers must fully validate and test any circuit before implementing a design based on an example in this section. Unless otherwise noted, the design procedures in Full-Range Centigrade Temperature Sensor are applicable.

LM50 LM50-Q1 typapp1_snis118.gif Figure 16. Centigrade Thermostat or Fan Controller
LM50 LM50-Q1 typapp2_snis118.gif
125°C full scale
Figure 17. Temperature To Digital Converter (Serial Output)
LM50 LM50-Q1 typapp4_snis118.gif
–40°C to 125°C; 100 Hz to 1750 Hz
Figure 18. LM50 or LM50-Q1 With Voltage-To-Frequency Converter and Isolated Output