JAJSNM5A December 2021 – August 2022 TMP9R00-SP
PRODUCTION DATA
The TMP9R00-SP device is designed to be used with either discrete transistors or substrate transistors built into processor chips, field programmable gate arrays (FPGAs), and application-specific integrated circuits (ASICs). Either NPN or PNP transistors can be used, as long as the base-emitter junction is used as the remote temperature sensor. NPN transistors must be diode-connected, and PNP transistors can either be transistor- or diode-connected. See Figure 8-2 for configuration options.
Errors in remote temperature sensor readings are typically the consequence of the ideality factor (η-factor) and current excitation used by the TMP9R00-SP device versus the manufacturer-specified operating current for a given transistor. Some manufacturers specify a high-level and low-level current for the temperature-sensing substrate transistors. The TMP9R00-SP uses 7.5 μA (typical) for ILOW and 120 μA (typical) for IHIGH.
The ideality factor (η-factor) is a measured characteristic of a remote temperature sensor diode as compared to an ideal diode. The TMP9R00-SP allows for different η-factor values. See Section 7.6.1.8 for more information.
The η-factor for the TMP9R00-SP device is trimmed to 1.008. For transistors that have an ideality factor that does not match the TMP9R00-SP device, Equation 4 can be used to calculate the temperature error.
For Equation 4 to be used correctly, the actual temperature (°C) must be converted to Kelvin (K).
where
In Equation 4, the degree of delta is the same for°C and K.
For η = 1.004 and T(°C) = 100°C:
If a discrete transistor is used as the remote temperature sensor with the TMP9R00-SP device, then select the transistor according to the following criteria for best accuracy:
Based on these criteria, TI recommends using a MMBT3904 (NPN) or a MMBT3906 (PNP) transistor.