AM335X peripheral/GPIO Pull up Power Rail Connection??

Sandeep N S

Hai,

As per the AM335X SCZ package datasheet I2C's(Just an example) Power ball is VDDSHVX. But pull up resistor for these interface is connected to 3.3V general supply. Is there any issue with this connection? Which power ball pull up is is recommended by TI???

Thanks and Regards

Sandeep

over 10 years ago

0 Biser Gatchev-XID over 10 years ago

TI__Guru**** 393215 points

Hi Sandeep,

I2C is not a good example, as the I2C I/O cells are open-drain. General requirement for external pullups is that they must be connected to the same power rail, to which the I/O pin is connected.

0 Sandeep N S over 10 years ago in reply to Biser Gatchev-XID

Intellectual 280 points

OK . Thanks.
If I am driving a LED using open drain GPIO (Power ball VDDSH5) with a pull up resistor ,, To which power i have to connect the pull up resistor???

0 Biser Gatchev-XID over 10 years ago in reply to Sandeep N S

TI__Guru**** 393215 points

VDDSHV5

0 Sandeep N S over 10 years ago in reply to Biser Gatchev-XID

Intellectual 280 points

But VDDSH5 have a current capability of 50mA only. So if I connect 3-4 LED's with 10 or 20mA current capability, it should be damaged . Right??
So can I take a external source with same ground supply???

Thanks and Regards
Sandeep

0 Biser Gatchev-XID over 10 years ago in reply to Sandeep N S

TI__Guru**** 393215 points

I definitely don't recommend that you drive LED's directly from the AM335X GPIO's. My suggestion is you insert a transistor in between. See page 6 of Beaglebone Black schematic for an example: http://elinux.org/Beagleboard:BeagleBoneBlack#LATEST_PRODUCTION_FILES_.28C.29

0 Sandeep N S over 10 years ago in reply to Biser Gatchev-XID

Intellectual 280 points

Am not meaning like that. I just take LED as an example load. Please excuse me. If I connecting load more than 50mA(like a buffere pull up) ,Can I use a external power source for it???

0 Biser Gatchev-XID over 10 years ago in reply to Sandeep N S

TI__Guru**** 393215 points

You should take into consideration maximum current handling capabilities of I/O cells. These are up to 4mA or 6mA for most pins (IOH and IOL from DC Electrical Characteristics tables in AM335X Datasheet Rev. G.). Loads that require larger currents must be buffered externally.

0 Sandeep N S over 10 years ago in reply to Biser Gatchev-XID

Intellectual 280 points

Thanks Biser for your support

Sandeep

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AM335X peripheral/GPIO Pull up Power Rail Connection??