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TPS62040 - Output is unstable

Matthew Day
Mastermind 36110 points
Other Parts Discussed in Thread: TPS62040

The TPS62040 output voltage appears to be unstable.  The switch node is very noise and there is a lot of jitter.  The duty cycle is not constant and changes from a value that is too low to a value that is too high.  What can be causing this problem?  I used the EVM's recommended components but generated my own layout.

  • 0
    TI__Genius 17240 points

    It is important that the layout also match that of the EVM.

    Poor layout can cause instability, poor line, load, and transient performance, excessive noise and jitter, less than maximum output current along with many other issues. 

    Here are a few examples of rules you have violated in your layout:

    • The input/output capacitor must be placed next to the IC with large pours/traces to the IC
    • The trace length from the feedback pin to the feedback resistor divider must be minimized
    • Analog ground and power ground should be separate then connected under the IC