MC33774 Internal acquisition circuitry

[Louis1916]

The customer's engineer reported that there was a 1K resistance at the CTn of the acquisition pin about MC33774, see the picture. For example, if the external power supply is 3.3V, CTn-1 and CTn+1 are both 4V, but the voltage collected by CTn is only 1.7V. How does it affect the acquisition of CTn acquisition?Can the internal acquisition circuit be shared? Thanks!

[RafaR]

Hi Louis

Before sharing my opinion I want to verify all the documentation.

What example or documentation is your design based on?

Have a great day and best of luck.

[Louis1916]

Hi Rafa
This 1K resistor is not added by design, but the board is abnormal and the resistor on the bench forms a series loop, thanks!

[RafaR · Accepted solution]

Okay

I just want to confirm, that the board is your own design and you used our schematics. (what document did you use?) to make your board, but your board has an unusually resistance between the Cn and CTn-1

Please follow the link below:

https://www.nxp.com/products/MC33774

Scroll to Documentation, in this section you must choose "secure files", if you do not have access, you must open a ticket to request access.

I recommend you read:

• “MC33774A data sheet rev 2.0”, here you can find more information about the internal circuit and representation (here is the representation of the cell voltage acquisition circuit.)
• “MC33774A cell balancing modes” & “MC33775A and MC33774A measurement”, information with more examples of the different balancing modes and how measurement the cells
• “AN13881 - MC33774A layout recommendation and BOM justification”, if you decide change the design of your board

I hope this information has helped you, please let me know if this information is enough, I have doubts if I am understanding you correctly.

Correct me if I'm wrong

Have a great day and best of luck.