TPS25981: Selecting E-Fuse to protect the batteries

Hi Jin,

JIAN JIN said:

Two 12V 18AH lead acid batteries could be reverse connected and this is the protection device. 

Can you share a block diagram showing how you want the connections and where you want to use eFuse and your load. I am asking this cause most eFuses don't have reverse polarity protection i.e. if battery is connected in wrong polarity, device will get damaged. eFuse do have reverse current blocking.

Also, can you confirm by 2x 12V batteries you mean your application voltage is 24V.

JIAN JIN said:

If the current draw is greater than 8 amps for 15 seconds on the batteries, we would like for the connection to be opened.

eFuses can limit current. They also have scalable current trip. Mostly the response is either immediate circuit break or limit current and thermal shutdown due to higher power dissipation. Do you want <15s response time or you want no response for 15s and then trip (blanking timer)

Best Regards,
Arush

Hi Arush,

Thanks for your quick feedback!!

For your last question "Do you want <15s response time or you want no response for 15s and then trip (blanking timer)"

My reply is: the connection is opened within 15 seconds.

For the block diagram and your question "can you confirm by 2x 12V batteries you mean your application voltage is 24V." You will find in below,

The two batteries are in parallel to increase the battery capacity. And there is a power source from the panel which has higher voltage (i.e. 13VDC) could charge the batteries in the normal application.

And there should be a efuse or circuit break which is close to each battery to protect each battery.

And if two terminals are connected in reverse poles, like below, the huge current would be go through the two batteries. Then the efuse or circuit break could work to protect each battery.

So, still the question, could you pls kindly advice the suitable MPN for eFuses or Circuit Break which could be the solution to this case? Thanks.

Hi Jian,

So you will need reverse polarity protection. TPS25947 is good fit here but it is uni-directional eFuse. TPS25981 and TPS25948 don't have this reverse polarity protection but with a system level workaround, they should work. 

By adding a diode between the device ground and signal ground, we can achieve reverse polarity protection. With this workaround, better recommendation would be TPS25948 (wcsp package, not suitable for some applications) and then TPS25981 (more current and QFN package).

What type of end application are you designing this for? 

Best Regards,
Arush

Hi Arush,

Thanks for your recommendation! We will consider to use TPS25948 and we are doing the evaluation for the feasibility of this solution. I will let you know if we have any further action. Thanks.

JIN JIAN