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TMP121: Idle when longer conversion time is used

Part Number: TMP121


I received a question from a customer of mine. They have a question on the interpretation of the datasheet of the TMP121, SPI temperature sensor.

In the table of the Electrical Specifications, page 3, it states a min and max time for the conversion time. These are shown in Figure 2 which results in about 50% cs_n high and low. 

When reading the section "Communicating with the tmp121” on page 5, it looks like you can divert from that. You could for example keep cs_n high for a longer time. The only thing, the sensor then goes into idle. 

Would the following implementation also work?

Conversion period of 500ms. A conversion time of more than 499 ms (so more than 320 max).

cs_n is kept low for only 15.5 us, to read out the data with a sck clock of1000 ns (100 ns min). See screenshot below:

  • Hello JuMar

    I am not sure what you are implying here. A new conversion begins every 500 ms, while a conversion takes 240-320 ms. So if you read once every 500 ms for a time frame of 15.5 us, then the device will provide you with the data for the last conversion. If the CS is high for more than one conversion time period of 500 ms then the device will go into Idle mode. However if the time period is interrupted then then a new conversion shall be triggered.