I2C acknowledgement problem and resistor pull-up

Thread Starter


Joined Oct 3, 2011
We are using a buffer for I2C interface signal's voltage level translation. Here our I2C host is OMAP3530 which is of 1.8V signal level and device is video ADC which is 3.3V signal level.So we are using a buffer for voltage translation.
When we try to access the Video ADC from OMAP3530, we are not getting the acknowledgement from the processor side.whose waveform are capture at the i/p and o/p the buffer

i/p of the buffer:
o/p of the buffer:

The internal pull-up resistor of the buffer is 10K and the I2C lines of video ADC is 2K2.The pull-up resistor used at OMAP processor is 4K7 which is fixed.
what is the equivalent pull-up resistor we can at the I2C lines of video ADC.
please comment on this....



Joined Apr 24, 2011
Your attachments did not copy as we're not subscribers to THAT board. Try again.

A schematic of the I2C portion is vital to understand your problem. Post one.

What do you use for the buffer? There are dedicated function IC's for this purpose. I've done level change on an I2C bus once (5V<->3.3V) using such a translator and had no issues.