Hi team
From the data sheet and other questions,
It was confirmed that it can be used with VCCA <VCCB and VCCA = VCCB.
I accidentally designed it with VCCA 3.3V and VCCB 2.5V, but I2C access is working fine.
I saw the SDA / SCL waveform of the A / B channel. The low drive is also made and the signal does not rise.
I am aware that it deviates from usage. I'm looking for a reason to support operation with VCCA> VCCB.
I want some advice.
thanks.
Hi Takayuki,
From the data sheet and other questions,
It was confirmed that it can be used with VCCA <VCCB and VCCA = VCCB.
The datasheet actually states B side should be larger than A side by atleast 1V.
You may be able to get it to work where the device still functions while A>B but deviating from the recommended set up means that the electrical parameters will likely no longer describe the device's characteristics accurately. The device was designed, validated, and tested for the condition of B > A by 1V. One of the major parameters affected when you don't follow this set up would be that the ViLc may drift lower. I2C compliant devices who drive low during a contention situation (SDA control hand off) may no longer be able to meet the ViLc requirment anymore. You may see corner cases where some units on boards can function correctly while others may not due to silicon variations or intermittent failures at higher temperatures.
I have seen customers successfully use the device where A side is equal or slightly larger than B side but from my stand point (a TI representative), I cannot recommend going outside of the datasheet specifications.
Now that being said, the big concern here is that the 2.5V bias on VccB no longer meets the datasheet's minimum requirement of 2.7V. I believe you are actually close to the device's undervoltage lock out threshold since the power supply recommendations also state a 2.5V threshold.
I believe this to be something that would require you to redesign the circuit/PCB.
-Bobby
