AD5272 potentiometer IC

Thread Starter

terrylai

Joined Oct 11, 2022
7
Hello all,

Do anyone have an idea that AD5272 potentiometer IC can have resistance output value when it is off-power?

BR,
Terry
 

Ya’akov

Joined Jan 27, 2019
6,856
Welcome to AAC.

While it doesn’t address your question explicitly, the datasheet does suggest in various places that VDD must be applied for the device to operate as a resistor. Then, there is this from the Table 1:

PNG image 2.pngPNG image.png

This parameter’s definition would be taken to mean power must be applied, since VSS and VDD would both be 0, making the terminal voltage range 0. Many other sections of the text suggest that power is required as well, and nowhere does it say otherwise, so—seems like the answer is, “no, it doesn‘t pass current when the VDD is not present.
 

Thread Starter

terrylai

Joined Oct 11, 2022
7
Thank you very much Ya’akov to provide some tips to me.

Actually I want to make a battery operated thermometer emulation device to save power. The temperature is monitored by a AD5272 temperature sensor. When I shut down the temperature sensor zone power and reopen it, the conversion cannot start again and loop forever. Do anyone know how to solve it? Thank you very much if you can provide a little tips to me. When it is normally start, the conversion can be done.
 

Ya’akov

Joined Jan 27, 2019
6,856
Sorry it is LTC2986 temperature sensor.
I don't completely follow your description of the problem, but are you waiting for reset to go high before attempting a conversion?

From the LTC28986 datasheet:

In the first phase of the start-up state all critical analog circuits are powered up. This includes the LDO, reference, charge pump and ADCs. During this first phase, the com- mand status register will be inaccessible to the user. This phase takes a maximum of 100ms to complete. Once this phase completes, the command status register will be accessible and return a value of 0x80 until the LTC2986 is completely initialized. Once the LTC2986 is initialized and ready to use, the INTERRUPT pin will go high and the command status register will return a read value of 0x40 (Start bit = 0, Done bit = 1). At this point the LTC2986 is fully initialized and is ready to perform a conversion
 
Top