TCAL6408: TCAL6408 - why just two I2C addresses?

Hi Thomas,

Tomasz Jastrzebski said:

It is not a question but a suggestion. Why do not you allow for four I2C addresses instead of just two?
Additional two addresses could be easily handled the same way DAC63004 does it, that is, by connecting ADDR pin to either SCL or SDA.
This would be a great improvement while pin and functional compatibility would be 100% retained. It seems like it is a really 'low hanging fruit'.

Ofc, I know that similar IC with more ports exist but it is not a desirable solution since it would require more long PCB traces which even may force us to add additional PCB layers.
In such context, using, let's say, four 8 port expanders, rather than two 16 port expanders would be substantially more convenient and actually dramatically cheaper.

This is a good suggestion, and I find this a good solution for I2C addressing. 

I think the major reason why we pursued just 1 ADDR pin as opposed to 2 in the past has been to be pin-2-pin with other competition. In general, if even one pin has a different use case, even in software, it has the potential for us to lose share in specific circumstance. For example, if our fixed I2C address bits are different then our competitors, we technically are not "electrically compatible" even if a few bits are flipped but everything else about the IC is electrically the same: VOL, IOL, ICC, VCC, etc. 

Another reason could be qualification purposes. If we release TCAL6408 with 4 address options, and the existing customer uses the 2 address option already qualified in their system, it might be difficult to sell the device because it would require a re-qualification of the device of which the customer might not want to spend the time + resource to accomplish. 

If the business opportunity is significant, we have made device spins in the past to accommodate. Please email me here at t-townsend@ti.com if you would like to start further discussion. 

Regards,

Tyler