Unconventional use of L9825

[Fred4]

In my project I use a L9826, 6 Outputs are used conventionally 2 outputs are not used.

In the same project I need to have 2 digital inputs (SPI) and I would like to know if I could use the two unused outputs of the L9826 as HCMOS inputs via the Fault status register; would this type of unconventional use be possible? Thanks

[Peter BENSCH · Accepted solution]

Welcome @Fred4, to the community!

You referred to L9825 in the title and L9826 in the text, so please correct one of them. Essentially, however, both devices have the same structure.

If you switch the unused outputs to non-active so that the driver MOSFET is disabled, you should indeed be able to use the relevant OUT as an input. Please remember to read the status register twice to be on the safe side, as the first value may still be incorrect. Please also remember that the threshold is 0.38*VDD, i.e. 1.9V for 5V, which differs from the usual value for CMOS inputs.

I'm curious to see what your test reveals.

Regards
/Peter

[Fred4]

Hi Peter,

thank you for your kindly reply.

Effectively I did a mistake while I'm using L9826.

I agree with your remark because I noticed in the datasheet that it is necessary to read the status register twice to have a reliable value, however the reading is circular and the values ​​are constantly updated. I will give feedback as soon as the tests are concluded.

Thanks, regards
Fred4