TMAG5231: Magnetic sensor operation flipped from expected operation?

Jon Neal

Part Number: TMAG5231

Hello,

I am using TMAG5231A2DQDMRR put a device in a low power state. Maybe I'm misreading the datasheet, but it seems that I'm getting the inverse operation I'm expecting.

The output of the TMAG5231 goes in to the enable pin of a MAX17223 (which is active high and works with a push/pull output), as shown in the schematic snapshot below:

My expectation is that the TMAG5231 outputs a high signal when there is minimal magnetic field (flux density below Brp) and outputs a low signal when there is a magnetic field (flux density about Bop).

However, what happens is that it outputs a low when there is no magnet nearby, and when I put a magnet near the IC it outputs a high. The opposite of what I want/am expecting.

For what it's worth, VBat is a 3V CR battery cell.

Am I misreading something?

Thank you!

over 1 year ago

+1 Isaac Lara over 1 year ago

TI__Mastermind 20800 points

Hello Jon,

Thanks for posting to the sensors forum!

The TMAG5231 has a couple of different options, the version you have specifically the TMAG5231A2D is actually an active high version of the device. Meaning that the operation is in fact inverted from what you are expecting.

A logic high device works as mentioned above when you have a magnet nearby it will exceed the Bop threshold and output a logic High signal when that magnet is removed and the magnetic field goes below the Brp value then the output will return to a logic low state. It sounds like what you are looking for is an active low device, meaning that when you have the magnet nearby it will hit the Bop threshold and yield and logic low signal.

Luckily most of our devices are actively low and the A2D variant you are currently using is our only active high device. You may be able to use the A1C as a suitable replacement it has the same thresholds as the A2D version the only notable difference is the sampling rate which is 10Hz compared to 20Hz. I have included a table from the datasheet below: