• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 78 subscribers
  • Views 249 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

High USB current on MSP430F5528

Christopher Payne
Intellectual 665 points
Other Parts Discussed in Thread: MSP430F5528

We are using the MSP430F5528 in our prototype for USB communication. While connected, the MCU draws a constant 8 mA. This is a problem for our application as it heats the board slightly. I noticed that it does not ever go into a suspended state while the PC it is attached to is active. I understand that the host is in charge of this, so I have no control over when it goes into a suspended state.

So I have a couple questions:

Is it normal for the USB to cause the MCU to draw 8 mA while connected? I know it is supposed to go into LPM0 while waiting for something to be received.

If it is not possible to lower this current, is there any way to turn off certain parts of USB while it is not active, but still be able to receive/send data when needed? So basically put it in a  suspended state while not sending or receiving.

  • 0
    Guru 227245 points

    If USB is active, then it needs to run its crystal and the (current-hungry) PLL to maintain the required 48MHz. According to the datasheet, the PLL is specified with a (maximum) current of 7mA.

    If the PLL is off, the USB can’t receive or send data, and switching it on (works only when you want to send, as it can’t detect incoming transmission while the PLL is off) takes some time.

    However, if the wiring is correct, it will draw this current form USB power, so it should be a don’t care.

**Attention** This is a public forum