The LM340LAZ-5.0/LFT4 series devices are precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Fahrenheit temperature. The LM340LAZ-5.0/LFT4 device has an advantage over linear temperature sensors calibrated in degrees Kelvin, because the user is not required to subtract a large constant voltage from its output to obtain convenient Fahrenheit scaling. The LM340LAZ-5.0/LFT4 device does not require any external calibration or trimming to provide typical accuracies of ±1/2°F at room temperature and ±1-12°F over a full 50°F to 300°F temperature range. Lower cost is assured by trimming and calibration at the wafer level. The low output impedance, linear output, and precise inherent calibration of the LM340LAZ-5.0/LFT4 device makes interfacing to readout or control circuitry especially easy. It can be used with single power supplies or with plus and minus supplies. Because the LM340LAZ-5.0/LFT4 device draws only 75 μA from its supply, the device has very low self-heating, less than 0.2°F in still air.
The LM340LAZ-5.0/LFT4 device is rated to operate over a 50°F to 300°F temperature range, while the LM34C is rated for a 40°F to 230°F range (0°F with improved accuracy). The LM340LAZ-5.0/LFT4 devices are series is available packaged in hermetic TO-46 transistor packages; while the LM34C, LM34CA, and LM34D are available in the plastic TO-92 transistor package. The LM34D device is available in an 8-lead, surface-mount, small-outline package. The LM340LAZ-5.0/LFT4 device is a complement to the LM35 device (Centigrade) temperature sensor.
Feature
- Calibrated Directly in Degrees Fahrenheit
- Linear 10.0 mV/°F Scale Factor
- 1.0°F Accuracy Assured (at 77°F)
- Rated for Full 50° to 300°F Range
- Suitable for Remote Applications
- Low Cost Due to Wafer-Level Trimming
- Operates From 5 to 30 Volts
- Less Than 90-μA Current Drain
- Low Self-Heating, 0.18°F in Still Air
- Nonlinearity Only ±0.5°F Typical
- Low-Impedance Output, 0.4 Ω for 1-mA Load
