How to use MC33789 PIN IN1~IN9 And Internal bias supply voltage

paul_shang · ‎07-23-2023

Hi

We want to Use MC33789 INX to detect Resistance property Sensor，How do we to design this part of the schematic?

And How to use the bias supply voltage?

If we configure a bias voltage to the INX, then this Bias voltage is equal to the voltage on the PIN INX ?So, it is also equal to the voltage on the Aout PIN(if configure this channel to Aout)?

paul_shang · ‎07-26-2023

Hi Tomas,

This sensor is a variable resistor. The range of resistance is from 125 Ω to 1050 Ω.The resistance value is used to feedback the pressure on the car seat. Used to detect whether there is anyone on the seat. Usually if the resistance is less than 325 Ω, we think that no one is in the seat. And When it is greater than 750 Ω, we think someone is in the seat.

TomasVaverka · ‎08-02-2023

Hi Paul,

Here is the answer I have just received from my colleague who is a bit familiar with this IC.

I checked again for it and below could be one solution. The Rsense inside MC33789 could reflect current drawn by Resistance sensor which uses NXP internal bias power supply. The conversion rate is Kconv which listed in datasheet.

Best regards,

Tomas

TomasVaverka · ‎07-24-2023

Hi Paul,

I am currently in the process if identifying the right person who is familiar with this pretty old Airbag SBC IC and could answer this technical questions. I will update this thread as soon as I have any news.

BR, Tomas

TomasVaverka · ‎07-25-2023

Hi Paul,

Please see below the answer I have received so far.

I am not quite familiar with this device and could you ask the customer to share the datasheet of Resistance sensor, then we could check how to connection with SBC?

BR, Tomas