BQ40Z60: Safety Mode

Hi Keith,

Before you get too far along with your design using bq40z60 we would like to make sure you have considered all of the options as well as the challenges of working with a such a tightly integrated solution.

We have found that many customers using bq40z60 have difficulty designing their board to pass EMI testing. This is due to the limited degree of freedom you have when laying out such an integrated solution which includes a switch-mode device. As attractive as it may sound to have the charging, gauging, and protection functions in one IC, in practice by using a separate charger and a separate gauge you get more flexibility and it can actually be easier to design. Not only can you choose from a wider range of chargers and gauges, but you can take advantage of newer technology and newer firmware. Popular choices for discrete multi-cell chargers range from standalone ones with integrated FETs like bq2417x or external FETs (for higher currents) like bq2461x to SMBus/I2C controlled chargers like bq2477x, among many others. The newest and most interesting charger is the buck/boost charger bq2570x which allows you to take any voltage input and charge any battery voltage stack, as well as take that battery voltage and boost or buck it back out to any target voltage. It’s great for USB Type-C and USB-PD applications. On the gauge side, the most popular new standalone gauge is bq40z50-R2 which has the most recent feature set and more extensive safety and protection options.

Of course TI is here to support you no matter which ICs you choose, but be sure to consider all of your options and don’t assume that integration is always the best.

a) The [SS] Safety Status bit on other devices such as the bq40z50-r2 is ORed with all of the Safety bits. If any safety bit asserts, SS is asserted. For the bq40z60, the function should be similar - I am working with the firmware team to confirm.

b) I am working with the firmware team to confirm. I will update this thread by the close of business on Thursday.

c) Are any of your safety bits asserted? Please ensure they are unasserted. Unsealing the device should clear the SS Flag.

Please let me know if the issue persists.

Sincerely,
Bryan Kahler

Hi Bryan,

a) have you had a response from your firmware team
b) any updates from your firmware team
c) the device is already unsealed? it is not obvious why the SS flag is set?

As a bit of background we already use the BQ40Z60 in a deployed product.

thanks,
Keith