Other Parts Discussed in Thread: BQ27541
Just some curiosity questions. Apple use what appears to be a variant of the BQ27545 in many of their cells, marked SN27545. From what we understand, the function of the device is the same, but it has different firmware, with potentially some additional software features.
The datasheet for the BQ27545, its functions, pinout, and its data/flash locations appears to all be relevant. When communicating with this device via an implementation of the HDQ protocol, we can do so as if its a BQ27545, and cannot detect a difference, beyond the obvious difference in firmware versions. We may have found a difference in the HDQ timing, but we haven't investigated this deeper.
We have noticed a trend with this prefix swap in Apple devices, where BQ is replaced with SN. The same occurred with the SN27541 (BQ27541), and some other, typically power/charging related ICs, like the SN2400AB0.
Are the SN prefixed IC's a custom part supplied exclusively to Apple/Foxconn?
Is the distribution of them controlled in some way?
Are we allowed to discuss the differences in firmware/hardware?
Where does the "SN" come from? Why not "AP" or "FC" ect
What level of information can you provide on these parts?
We would love to know more about where they come from, whats different about them, and why there is no information on them available from TI. Any information you could provide would be useful