TMS320F28379D: 5V eternal source for LAUNCHXL-F28379D board

Hi lio,

lio messi said:

I have to remove JP2, JP3, and JP6. However, removing JP2 isolates the ground of the external 5V from the USB ground. Is it correct? Shouldn't I connect these two grounds to each other for proper functioning of the board?

The User's Guide is assuming you are supplying 3.3V externally as well as 5V. This is to make the configuration completely isolated from the XDS100 debugger side of the board.

lio messi said:

Besides, in schematic design files given in C2000, there is a 0 ohm resistor (R25) in parallel with JP2 ! But I can't find it on the launchpad board. Is this resistor really exists?

The pads do exist on the board, but they are underneath ICs U5 and U7. You would have to de-solder U5 and U7 to get access to the pads.

Best,

Kevin

Thanks for the reply Kevin,

In configuration that JP2, Jp3, and JP6 are not connected, if I supply the 5 V externally from J16, is it necessary to provide another supply for 3.3V input of J10 ?

Should JP1 be connected or disconnected in this configuration?

Regards,

Hi lio,

lio messi said:

if I supply the 5 V externally from J16, is it necessary to provide another supply for 3.3V input of J10 ?

Yes it is. There is no 5V to 3.3V converter on the C2000 device side of the board.

lio messi said:

Should JP1 be connected or disconnected in this configuration?

The configuration in the User's Guide is meant to have JP1 (3.3V) and JP2 (GND) disconnected to completely isolate the xds100 side from the C2000 DuT side. I think it would defeat the purpose of the isolation if you supplied 5V externally, but 3.3V from the xds100 side of the board (USB 5V stepped down to 3.3V) as you'd need to connect the grounds.

Best,

Kevin

Hi Kevin! 

About JP1, it is not mentioned in table 2 on page 6 of User's Guide! Please consider revising it. Because it would confuse users.

What should the current rating of these 5V and 3.3V power supplies should be? Can I use AMS1117-3.3 to convert 5V to 3.3V for supplying the 3.3V pin of the DSP?

Regards

Hi lio,

It says "To supply 3.3 V to the device in an isolated configuration, see Table1" above table 2 for this purpose, but maybe it isn't clear. I'll make a note to look into this for a revision of the doc.

lio messi said:

What should the current rating of these 5V and 3.3V power supplies should be?

It's hard to say for the 5V, since it sounds like you may have an external board being powered as well. When using the USB for 5V to 3.3V conversion on the board 500 mA max current is offered, so no more than that should be good for powering the LAUNCHXL-F28379D. I don't have any current measurement data for the LaunchPad, but I'd imagine 500mA isn't even needed. You can refer to the F28379D datasheet for device current consumption.

lio messi said:

Can I use AMS1117-3.3 to convert 5V to 3.3V for supplying the 3.3V pin of the DSP?

You mean from an external plug-on board? Sure, I don't see why not. A DC/DC is used for the USB 5V to 3.3V on the LP using TPS62162.

Best,

Kevin

Hi Kevin and thanks for the reply.

It is now crystal clear to me.

Best regards