Other Parts Discussed in Thread: TPS62136, TPS82130, TPS62140A,
What happens if the SYNC pin is left open? Does that line have an internal pull up or pull down?
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Hi Chris,
Thanks for your response. I'm working with an existing design where that mistake was made. I intend to fix future designs by connecting the SYNC to the 12V that is coming into the TPS62110 (it's being used to regulate 12V down to 3.3V). However, I'm wondering about the assemblies already completed - if I look at the SYNC line with my scope probe, it appears to be solidly at 5V, which I believe would register as a high input on the SYNC line. Do you see any risk in leaving those assemblies alone?
Hi Chris,
Thanks again for your responses. You're right, the probe impedance can affect the pin's state. I do think it tends to float high by virtue of the leakage current charging up parasitic capacitance at that pin. But now I have a different question: I experimented pulling the SYNC pin High and Low, and then looked at the SW waveform at pin 14-15. In both cases, I get a 3.3V output as desired, but I am puzzled by the SW waveforms. Could you possibly explain what I am observing?
The first picture is with SYNC High, the second picture is with SYNC Low. I I see:
Hi Chris,
You were right, changing to a ceramic made the switching pulses much more uniform (see below). I will make the change for future boards. Is increased ripple the only performance downside of using the tantalum, or is there anything else I should be worried about on existing boards?
Thanks,