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Output Noise Specification for USB DCP

Jory Olson
Prodigy 120 points
Other Parts Discussed in Thread: TPS2511

The specification for the TPS2511 does not indicate anything about the expected output noise level.  BC1.2 doesn't say anything about output noise or ripple either.  However, I have several USB chargers (DCP) that have so much noise that the touch screen on my iPhone 6 will not work when charging.  Clearly the output noise is important!

Are there industry standard specifications for the output noise and ripple for Dedicated Charging Ports (DCP)?

  • 0
    TI__Intellectual 2795 points
    Yes, as you point out, BC1.2 is battery charging specificaiton, no any noise and ripple spec. As for the TPS2511, one USB power switch + DCP_Auto charging scheme provide the realted charging ID. For your application, the noise and ripple should be from the up-stream converter, no matter with TPS2511. The noise and ripple should be defined in some EMI/EMC paper.
  • 0 in reply to Milo Zhu
    Prodigy 120 points

    Yes, the noise and ripple would be determined by the upstream offline SMPS.  The EMI requirements are only part of the requirements.  There are reports of excessive ripple causing the PCAP touch panels on some devices to misbehave when plugged into Dedicated Charging Ports (DCP) with excessive ripple and noise.  I'm trying to figure out how much noise is too much in the context of the PCAP touch panel.