PSoC 5: Opamp Startup Glitch while used with VDAC – KBA226422

Version 4

    Author: VasanthR_91           Version: **

     

    Question:

    PSoC® 5 opamp shows a glitch on startup. How to tackle this problem?

     

    Answer:

    PSoC 5 opamp shows a glitch on startup while used along with VDAC. As the Opamp has dedicated output pins which are always bonded to opamp, there is no way to prevent these glitches from appearing on pins. The glitch can be around 1 V in amplitude and can have a duration of 100-200 ns.

     

    Figure 1. Glitch Observed

     

    Possible solutions to this problem include:

    1. Filtering out the glitch pulse using an RC filter.
    2. Reducing the duration and amplitude of the glitch by keeping the VDAC output zero before startup.
    3. Using an additional pin to route the opamp output.

    Use pins which are closer to the dedicated pins as the additional routing resistance will appear on the opamp output. This connection will be made only after startup, avoiding the glitch from appearing on the pin.