PCA9507

[Nooneuser123]

HI All,

I'm currently using DP PCA9507 in my design and am experiencing some issues related to bus capacitance and the SDA line always being at 0. I have connected the PCA9507 in series between the master and slave and used it in an HDMI application.

As per the application note, the SCL lines do not need to have pull-ups, but when I probe, I always get a reading of 0 on the line, and my board is not working as expected.

Additionally, according to the application note, SCLA should be connected to SCLB, but I have connected SCLA to SCLA. Will this create any issues? Also, the power rails are at 5V on both sides in my slave section.

Please take a look at this and help me resolve this query as soon as possible. Your assistance will be greatly appreciated.

Spoiler

[Nooneuser123]

Hi Team,

When the PCA9507 Buffer is placed in my circuit am getting the SCL and SDA bus capacitance as 1.5nF or 1.9nF but as per the spec it should be <50nF to pass the I2C testing .

When i remove this IC and measure it i could get the buscapacitance as less than 50nF and my test passes in the complaince.

could you please help to guide why am getting huge capacitance in nanofarads instead of picofards. please help me out on this matter as it is very urgent,

[Nooneuser123]

Hi Team,

I still didnot get the answers yet for my question. Am getting the DDC SCl, SDA lines capacitance values around 1300pf instead of 50 pf as per I2C Specification . Is there any reason why am getting more value ? is it because of the I2C redriver buffer capacitance ? is it supposed to be this way ? Plese help to reply at the earliest.

[guoweisun]

HI 

1: Why use two PCA9507 to connect the HDMI cable? for extend the communication cable?

2: add the pull up in the last PCA9507 SDA pin on HDMI display.

[Nooneuser123]

Hi Team,
Please find my comments:

1. Iam using a cable to extend my communication line from one end to the other end, both the ICs are not in the same PCB they are connected in 2 different pcbs.
2.as per the application it says no need to adding pullup in SDA line if used in display function.

[guoweisun]

Hi

1: How long did you extend this IIC between boards?

[Nooneuser123]

Standard HDMI cable less than <1M

[guoweisun]

Don't suggest use the PCA9507,you can select the PCA9614/5/6 for long distance extension.

[Nooneuser123]

Right now board is designed with PCA9507. Can you tell me if the series connection that i drew is correct ? its seems to be different than the application design. We have designed the source board and some other customer designed Sink board so the connection ended up being this way PORT A to PORTA for SCL and SDA.

Also is it required to use pullup on SDA in the sink side because the datasheet says no.

[guoweisun]

The connection is no problem,side B can't be connected with side B or other static offset structure port.

[Nooneuser123]

Ok, then do we need to mount the pullup on the SDA lines in sink side.

[guoweisun]

You can also try the low speed test again.

[Nooneuser123]

Hi Team ,

can you please help to provide the explicit answers to my questions.
1. do we need to mount pullup on SDA or not ?
2. porta to porta connection is correct or not between source and sink?

[guoweisun]

can you please help to provide the explicit answers to my questions.
1. do we need to mount pullup on SDA or not ?

[gw]Yes you need.
2. porta to porta connection is correct or not between source and sink?

[gw]correct.

For your application I suggest your select PCA9615 for long distance connection to replace PCA9507

[Nooneuser123]

I still didnot get the answers yet for my question. Am getting the DDC SCl, SDA lines capacitance values around 1300pf instead of 50 pf as per I2C Specification . Is there any reason why am getting more value ? is it because of the I2C redriver buffer capacitance ? is it supposed to be this way ? Plese help to reply at the earliest.