Hello,
I am a consultant engaged in a detailed design review for a client who is using this part in their design. They are presently stuffing a 0.1uF capacitor for the CP1/CP2 charge pump component instead of the recommended datasheet value of 0.01uF. While I understand the fundamental importance of following datasheet recommendations, "does not follow datasheet recommendation" is not sufficient rationale for presenting a need for change to the client for a medical device in current production. I need to present if their part selection would change the behavior/performance of the charge pump in a way that would create a specific problem, and what that problem would be, as the rationale for design change.
I initially opened a support ticket (CS0502962) for this question and was pointed to the following thread for general performance rationale:https://e2e.ti.com/support/motor-drivers/f/motor-drivers-forum/716344/drv8818-capacitor
If you dig into this thread, you will see that the commenter said to keep the ratio of VCP/CP between 1:2 and 2:1 for things to be OK, but the DRV8825 datasheet is recommending VCP cap=0.1uF and the CP1/2 cap=0.01uF. That's a ratio of 10:1. So the DRV8825 datasheet recommendations do not align with the behavior/performance rationale presented in the thread.
Please advise and thank you for your help in advance.
Chris