Azoteq have changed the part numbers of the IQS5xx devices from 'A000' to 'BL'. This is to distance the touch controller purchased from any specific product firmware release, such as the IQS5xx-A000 or IQS5xx-B000. The 'BL' indicates that the device is pre-programmed with an I²C bootloader(BL). The application firmware is then programmed by the end customer during product testing and manufacturing, making the part number and controller more generic for any future application firmware.
On the IQS5xx-B000 (the latest Azoteq trackpad controller platform), the customer already creates a custom HEX file,including the required setup and tuning parameters for that specific hardware. This then needs to be programmed onto the device, negating any application firmware that is already pre-programmed on the controller.
Here is a table showing the part number change for all three controllers in the IQS5xx family.

Brand of Product：	Azoteq
Part#：	IQS5xx family 、 IQS5xx 、 IQS5xx-A000 、 IQS5xx-B000 、 IQS525A000QNR 、 IQS525BLQNR 、 IQS572A000QNR 、 IQS572BLQNR 、 IQS550A000QNR 、 IQS550BLQNR 、 IQS550 、 IQS572 、 IQS525 、 IQS5xxBLQNR More Part#
Product Category：	More
Application：	More
Data Type：	PCN/EOL More
Safety & Environment Standards：	More
Operating Temperature：	Please see the document for details
Qualification Grade：	More
Qualification Approval：	More
Package：
Language：	English Chinese Chinese and English Japanese
Date of Creation：	1 March 2016
Version Number：	Revision 1.0
Data Encoding：	ACN_5XX_01
Data Size：	308 KB