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# TMP61: room temperature resistance accuracy

Part Number: TMP61

Hello,

I have a question about TMP61 thermistor resistance @25oC.

Datasheet says it is 10Kohms typical, 9.9Kohms minimum and 10.1Kohms maximum.

However, in the page of “TMP6 Table” in “TMP6131 System Parameter Calculator v1.0”, it different from the datasheet spec as follows.

 T[°C] R nom[Ohm] R min[Ohm] R max[Ohm] 25 10145.97969 10044.5199 10247.43948

On the other hand, in the “NTC table”, NTC resistance @25oC is 10Kohms typical, 9.9Kohms minimum and 10.1Kohms maximum, it is the same as TMP61 datasheet spec.

 T[°C] R nom[Ohm] R min[Ohm] R max[Ohm] 25 10000 9900 10100

Why does “TMP6 Table” in “TMP6131 System Parameter Calculator v1.0” use different room temperature resistance value from datasheet spec?

According to “TMP6131 System Parameter Calculator v1.0”, TMP61 voltage error @ room temperature looks larger than NTC. But TMP61 datasheet says room temperature resistance accuracy is tha same as NTC, 10Kohms +/- 1%. I am confused.

Best regards,

K.Hirano

• Hi K.Hirano,

The exact resistance of TMP61 varies slightly depending on biasing method, this is nature of silicon thermistor. For example, in the table you reference the TMP61 is biased with a 200uA current source. The following table shows TMP61 biased in a 2.5V resistor divider and it shows different R values at 25C.

However, even in the 25C table you show for TMP61 in calculator tool, the tolerance at 25C is still +/-1%. ((Rnom - Rmin)/(Rnom) * 100)

Jalen

• In reply to Jalen Tate89:

Jalen,

I see, thanks a lot!

Best regards,

K.Hirano