DS90UH949 I2C DDC

Thomas%20Sagcob

Other Parts Discussed in Thread: PCA9306

Hi,

DSD90UH949-Q1: On our board the DDC-IF is used only internal so it doesn't has to fulfil the HDMI-Spec. We've plugged the I2C-IF and the DDC-IF together with an I2C master to a 3V3 bus.

Question:

1.) how are the threshold voltages for VIH, VIL and VOH defined? (e.g. VIH = 0,7*VDD, VIL = ...)

2.) to which supply voltage are the threshold related to? (e.g. voltage supplied at RX_5V, ...)

3.) when connecting the DDC and I2C ports together, is it allowed to supply "DS90UH949/pin43 = RX_5V" with 3V3 to meet the threshold requirements?

Thanks in advance

Thomas Sagcob

over 9 years ago

0 Eric Hackett over 9 years ago

TI__Guru 74252 points

Thomas,

Your post has been moved to the High Speed Interface forum for more appropriate support.

Regards,

0 Jason Blackman over 9 years ago

TI__Genius 14015 points

Hi Thomas,

The DDC_I2C port was defined with 5V pull-up in mind, but the VIH threshold is low enough to support 3.3V as well. The VIH level in the datasheet right now is 0.7*VDD,DDC where VDD,DDC is 5V. This works out to 3.5V, but as I said the actual threshold is much lower. We are in the process of updating the datasheet to show this value as being fixed 2.5V maximum.

It is acceptable to connect both ports together and run off of 3.3V pull-ups.

Thanks,
Jason

0 Thomas%20Sagcob over 9 years ago in reply to Jason Blackman

Prodigy 70 points

Hi Jason,

many thanks for your fast answers.

In addition, can you give me also the "new" values for VIL and especially for VOL.

Threshold for VOL might be critical when using a levelshifter (e.g. PCA9306) to 1V8 domain.

Thanks
Thomas