VBus Launchpad connection

Hector Tosado

Other Parts Discussed in Thread: EK-TM4C123GXL

Hello,

I'm going to be trying to connect my Launchpad from an external power source other than the USB port. There is an VBus socket on the bottom left of the Launchpad that can be connected with a JST connector and maybe other similar types. I plan to connect a 5V power supply which should be in the operational range of the launchpad, knowing that this same voltage is the amount it gets from the USB connection. I was wondering if anyone knew if any precautions I needed to take into consideration before hand. I plan of having my program already loaded into the MCU so it should be just a matter of plug in the VBus with a 5V source and let the program run?

Thanks,

over 12 years ago

0 Stellaris Dexter over 12 years ago

TI__Genius 17225 points

Hector,

If you are only providing a single source then connecting to those 5V pins is OK. Those pins are after the power select switch so they get power from either USB Debug or USB device connection. Thus the power switch will not be able to turn off the launchpad. It also means that your 5V will be presented to whichever USB port is selected by the power switch.

The only concern would be if you have more than one connection at the same time. In that case a diode or some other method should be used to prevent the two sides from contending against each other.

Dexter

0 Sham Sunder over 9 years ago in reply to Stellaris Dexter

Prodigy 130 points

Hello,

Can i connect my launchpad to external power supply of 3.3V? Hope it will not cause any problem with regulator (as 3.3V at output pin will be present without any voltage on input). Off course launchpad will not be connected to usb, i just wana use it as a controller in my prototyping board.

Thanks

0 Amit Ashara over 9 years ago in reply to Sham Sunder

TI__Guru**** 244400 points

Hello Sham

Which LaunchPad is this?

Regards
Amit

0 Sham Sunder over 9 years ago in reply to Amit Ashara

Prodigy 130 points

Hi Amit,
Sorry for ambiguity. The launchpad is EK-TM4C123GXL.
Thanks

0 Amit Ashara over 9 years ago in reply to Sham Sunder

TI__Guru**** 244400 points

Hello Sham

It is not a good idea to supply a voltage directly when an LDO is in place. The reason is that you cannot really know that if the LDO on its output pin may sink in current when there is no input voltage available. The better way (and of course it will cause rework) is to remove the U8 component and then use H22 to supply 3.3V

Regards
Amit

0 Sham Sunder over 9 years ago in reply to Amit Ashara

Prodigy 130 points

Hi Amit,
Thanks for reply....But to avoid rework i would prefer to apply VBUS of 5V to left-bottom given terminals of launchpad, hope it will be fine.

Thanks

0 Amit Ashara over 9 years ago in reply to Sham Sunder

TI__Guru**** 244400 points

Hello Sham,

When you do apply a 5V make sure the switch is in the position such that the USB 5V and the external 5V do not get connected.

Regards
Amit

0 Sham Sunder over 9 years ago in reply to Amit Ashara

Prodigy 130 points

Hi Amit,
Yes, when i will connect 5V, the launchpad will not be connected to any of USB ports.
Thanks

0 Amit Ashara over 9 years ago in reply to Sham Sunder

TI__Guru**** 244400 points

Hello Sham

That should be fine then.

Regards
Amit

0 Nguyen Toan over 8 years ago in reply to Amit Ashara

Prodigy 30 points

Hi Amit,

In my project, I need connect to both USB debug for serial and also external power supply ( since I need control motor and the usb can not supply enough current )

How can I connect the wire without broken the board.

Thank you

0 Amit Ashara over 8 years ago in reply to Nguyen Toan

TI__Guru**** 244400 points

Hello Nguyen,

It is not clear what you want to do? If the USB debug is being used then power will come from the USB debug port.

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VBus Launchpad connection