LM5067: Suggestion for using LM5067 in BMS for pre Charging

peeyush Chauhan

Part Number: LM5067
Other Parts Discussed in Thread: TPS23521, TPS2399

Hello Ti

I am going though a inrush problem with BMS . By using a resistor to pre charge the load require the high wattage resistor or in case where load is short circuit the resistor got burnt. So i came up with the idea to use negative hot swap controllers to inrush the current limit . after the inrush event is over my main MOSFETS will take over. So the problem is the Load Capacitance is varying (if consider 2-3uf per watt) depending upon the DC Dc or Traction Inverter used. My system is 16S ,50 amps so roughly 2900- 3000W load can be operated at output. So by going through the LM5067 calculator i choose lager cap to be around 10,000uf for which i got start up time to be 121ms and for 1000uf cap its around 12ms.. So my question is if i choose the fault time according to 10,000uf the falut time will be 470.59 ms at 10 amp current. So if puts a lower value cap instead of 10,000 one .. i cant change the fault time . and if load get short ckt during this additional time continuous constant current will be drawn. How can i handle this situation..

Thank you

Regards Peeyush Chauhan

over 4 years ago

0 Avishek Pal over 4 years ago

TI__Mastermind 39780 points

Hi Peeyush,

Welcome to E2E !!!

Thanks for reaching out to us. We will get back to you by Monday (31/May/21) end of the day.

0 peeyush Chauhan over 4 years ago in reply to Avishek Pal

Prodigy 20 points

ok sir..

0 Rakesh over 4 years ago in reply to peeyush Chauhan

TI__Guru** 105531 points

Hi Peeyush,

Do you have any timing constraint for the startup? If not, I suggest to use soft-start mode of start with TPS23521 instead of power limit mode of start with the traditional hot-swap controllers, to safely charge the large output capacitors. For these kind of use cases, TPS23521 is an ideal fit. Please refer the product datasheet, application report https://www.ti.com/lit/an/slvae07/slvae07.pdf and let me know if you have any questions.

Best regards, Rakesh

0 peeyush Chauhan over 4 years ago in reply to Rakesh

Prodigy 20 points

Hello sir Actually the purpose here to use lm6057 is also to use the circuit breaker function. The whole process i am thinking is that . The Hot swap controller will start the pre charge session with the soft start and my mcu will wait for the PG signal. If all goes well my mcu will turn Off the hot swap and energies the main mosfet path.. In case of Shot circuit i want hot swap will detect that and notify to mcu.. Time is not the Issue for me i Can spend long time in Pre Charge..

0 peeyush Chauhan over 4 years ago in reply to peeyush Chauhan

Prodigy 20 points

And one thing sir .If this hot swap controller initiates and it has a shorted output . means Shunt voltage is above Circuit breaker link . will it instantly turns mosfet off or it will wait for the timer .

0 peeyush Chauhan over 4 years ago in reply to peeyush Chauhan

Prodigy 20 points

SIr IS TPS2399 is also the part I can go with for your suggestion to use soft-start mode to control the di/dt and increase the the fault time above the SS time. The only problem I have with this device is circuit breaker operation..Please enlighten me.

0 Rakesh over 4 years ago in reply to peeyush Chauhan

TI__Guru** 105531 points

Hi Peeyush,

For an overload event, all hot-swap controllers wait for the fault timer to expire to switch-off the hot-swap MOSFET.

So, I don't see any advantage in going with TPS2399 controller.

For the below... If you turn-off the hot-swap, it won't be able to detect any fault. The hot-swap should always be in enable state to detect the power path faults.

Regards, Rakesh

0 peeyush Chauhan over 4 years ago in reply to Rakesh

Prodigy 20 points

Sir the motive of turning off the hot-swap is that my BMS is 16s , 50 amps with main SCD limit to be 200AMPS. My Aim is to remove precharge resistor and use hot swap.. With 3-4 amps I will charge the capacitors and make the current limit to be doubled.by this I can spend much time charging the caps which I cant do with Resistors. i only want hot to detect falts prior to main mosfets turning on.. I have a SCD latch with main mosfets...

0 Rakesh over 4 years ago in reply to peeyush Chauhan

TI__Guru** 105531 points

Hi Peeyush,

Ok. Understood.

You can use LM5067 to pre-charge the output cap. Please get an EVM and evaluate.

Let us know if you have any questions during evaluation.

Best Regards, Rakesh

0 peeyush Chauhan over 4 years ago in reply to Rakesh

Prodigy 20 points

Thank you sir.. I require some help in choosing the MOSFET .I have gone through LM5067 calculator with 10,000uf cap I require 640 ms start time at 4.3 amps current . So after the inrush even I need to turn it off . tool is suggesting SOA breach So how I can choose the mosfet ..I don't want to drive any load on it..Thanks

0 Rakesh over 4 years ago in reply to peeyush Chauhan

TI__Guru** 105531 points

Try with SUM80090E

Power management

Power management forum

LM5067: Suggestion for using LM5067 in BMS for pre Charging