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.
Hello,
I have a design with the TMS320F28069 - and am using the Control Card as a reference - (ISO version) -
I have a question regarding page 4 of the attached schematic - 0363.F2806XISO-CONTROLCARDR0.3-SCH.pdf
If the 5V0 source is generated from the Control Card Docking Station - and the USB MICRO AB is plugged in -
and U200 is 'ON' - (D200 will be on if VBUS > +5V + Vf D200) - doesn't this cause a short of the USB VBUS voltage
and +5V?
I have one of these boards - so I can do some testing on my own - but I wanted to ask how this is supposed to work - I can imagine the algorithm is something like this: (I haven't reviewed the firmware) -
Voltage on VBUS_DET?
If yes - do not enable USB_ENA, if no - enable U200.
Is there a requirement on the '069's USB Bus to always have a VBUS voltage present once the USB module is enabled?
Thanks!
johnw
Oh - the diagram - it is referring to the internal ESD diodes in the '069 to clamp the voltage - correct?
jonw,
I've asked Brett to comment on this topic, he owns the controlCARDs. He's back in the office tomorrow.
Chris,
OK - I also have been asking about the max freq the HRCAP module can handle - I think it is ~ 17.15 MHz - would
be great to get an answer on that one.
Thanks For Your Help,
johnw
John,
Sorry for any delay. I kept trying to get to this post as I was out.
External Diodes on USB: The diagram shown refers to the internal diodes in the MCU. That may be adequate. However, it is good practice to have extra protection. External ESD diodes would probably be preferred and especially on this line. Putting ESD diodes on DM and DP are also not bad ideas just make sure that you use a USB diode rated to the USB speed you wish to use so that the diodes don't load the line.
Is there shorting between USB power and the docking station power: They are shorted when EPEN is high (the MCU is trying to be the host) and ID is low (the OTG cable is telling the MCU that it is the USB device). In general, the type of USB you want to use (OTG, host or device) will determine the best hardware implementation. The implementation shown in the controlCARD should work for all, but may be more than necessary in many circumstances.
Thank you,
Brett