• State
  • Locked Locked
  • Replies 6 replies
  • Subscribers 64 subscribers
  • Views 1264 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS63061: What's the input impedence of Vin pin?

zhu
Expert 1925 points
Other Parts Discussed in Thread: TPS63061

Hi,

We are using an USB port as one of power sources of TPS63061 on our board, the USB port is quite far from the TPS63061(about 120mm long track, in 15mil width), one thing we don't understand is, when it approch TPS63061, the voltage drop to only 2.7V, then, after pass a protective diode, it drops to 2.25V which is not in work range(2.5V ~ 12V) of TPS63061.

So, why this would happen?  What's the input impedence of Vin pin? how to fix this issue?

Thanks in advance.

Zhu

  • 0
    TI__Guru**** 191445 points

    15 mil etch width is probably not sufficient for a power trace of that length.

  • 0 in reply to JohnTucker
    Expert 1925 points

    John, thanks for your reply.

    Yeah, sounds like increasing the trace width should be a good solution.

    So I soldered another wire in parallel with this trace, to see what would happen with a wider width, but, instead of a higher voltage before the diode(which was 2.7V), it's 2.6V now, 0.1V lower.

    Why?

  • 0 in reply to zhu
    TI__Guru**** 191445 points

    I can't see how adding that wire would increase the losses.  Can you post your schematic and layout?

  • 0 in reply to JohnTucker
    Expert 1925 points

    Of course, John.

    As you can see, there are 2 power sources, 1 from USB micro-B port, the other from P6, which is connector for 4 alkaline batteries in serial.

  • 0 in reply to zhu
    TI__Guru**** 150610 points

    I suggest you test with a regular power supply instead of a USB cable and debug this setup first.  Measure the voltage along its path from connector to switch, etc.  See where a big drop is.  You might also disable any load on the input voltage (i.e. TPS63061) or disable the load on the TPS63061 to reduce the current drawn from the input.

  • 0 in reply to Chris Glaser
    Expert 1925 points

    There is only 1 component(except a 0.1uF and a 10uF capacitor) that have connection with net VBUS, which I soldered off to confirm it don't make any voltage drop, so, there is nothing but the long trace that can drop the voltage, which have a measured resistance of 0.6ohm.

    About the output current, it's nearly 0, so I don't think TPS63061 is in a working state

    If I use a  regular power supply of 5V and solder it by wires to some points near the TPS63061, it can work.(output a voltage of 5.1V, current of 7mA)

    Zhu