BQ24616: Schematic review without DPM enabled

Noel Binny Abraham

Part Number: BQ24616

I would like to have a schematic review done for the aforementioned part number. I am using it for one of my projects to design a charger with 28V input, 22V output at 10A charging current. I've designed a schematic for the same and i request one of your engineers to take a look at it before i move ahead with the PCB design for the same. The board is configured without DPM/DPPM . The schematic has been attached below for your reference.Schematic_6S_Charger_BQ2461x TI review.pdf

over 2 years ago

0 Michael Emanuel35 over 2 years ago

TI__Mastermind 41935 points

Hello,

My schematic review is as follows:

1. Diode D1 is not optional and is required for bootstrap circuit.

2. Configured for 10 A charge current, 100 mA precharge current, and no input current limit.

3. VREF rail can only supply so much current, I recommend pulling up STAT1, STAT2, and PG through adapter but with at least 10 kOhm pullup to respect the 5 mA test condition through each pin when open drain is on.

4. Please see Table 4 of the datasheet. We recommend 3.3 uH inductor and 40 uF output capacitor for 10 A charge current.

5. Confirming 21.189 V charge voltage regulation.

Regards,

Mike Emanuel

0 Noel Binny Abraham over 2 years ago in reply to Michael Emanuel35

Intellectual 550 points

Michael Emanuel35 said:
Confirming 21.189 V charge voltage regulation.

We are using it to charge a 6S NMC. So that means peak voltage is 25.2V. So if it is being regulated at 21.189V how does it act as a charger? This is assuming i interpreted your reply correctly (stating that it is a buck converter.)

Michael Emanuel35 said:
Please see Table 4 of the datasheet. We recommend 3.3 uH inductor and 40 uF output capacitor for 10 A charge current.

Yes but other this configuration gives us a 10A output current with good ripple values within the resonant frequency range provided in the datasheet. Should i change the design to what is being recommended? I believe the components that has been given in the schematic above does the work too without much loss in performance. Correct me if i am wrong please.

0 Michael Emanuel35 over 2 years ago in reply to Noel Binny Abraham

TI__Mastermind 41935 points

Hello,

What I mean by 21.189 V charge voltage regulation is that is what the battery will be charged to. If you desire 25 V, you need to change the VFB divider. What is your input voltage? The input voltage always needs to be higher than the output voltage.

Ultimately how you design the ripple is up to you. Using a higher value inductor will give higher DCR which translates to lower efficiency. The tradeoff is ripple to efficiency.

Regards,

Mike Emanuel

0 Noel Binny Abraham over 2 years ago in reply to Michael Emanuel35

Intellectual 550 points

Michael Emanuel35 said:
What I mean by 21.189 V charge voltage regulation is that is what the battery will be charged to. If you desire 25 V, you need to change the VFB divider. What is your input voltage? The input voltage always needs to be higher than the output voltage

We are planning for a 28V input to charge a 6S battery. The values for VFB divider used is wrong.
I believe a 1.1Meg and 100k ohm divider should do the trick for a 25.2V output regulation?

+1 Noel Binny Abraham over 2 years ago in reply to Michael Emanuel35

Intellectual 550 points

Michael Emanuel35 said:
no input current limit.

The datasheet states that "If DPM feature is not required, ACN and ACP can be tied to VCC and ACSET can be tied directly to VREF. " This is is the reason i did not include input current limit. I wanted to confirm whether i can use the ACSET or not for input current limit even when i do not require DPM

+1 Michael Emanuel35 over 2 years ago in reply to Noel Binny Abraham

TI__Mastermind 41935 points

Hello,

Yes a 1.1 Meg and 100 kOhm resistor would give 25.2 V charge voltage regulation. Please make sure you control the input, as the maximum recommended input voltage is 28 V.

While it does not say the quote, "If DPM feature is not required, ACN and ACP can be tied to VCC and ACSET can be tied directly to VREF." in this datasheet, the same principle should apply. Please test according to your application.

Regards,

Mike Emanuel

0 Noel Binny Abraham over 2 years ago in reply to Michael Emanuel35

Intellectual 550 points

Hi again Michael Emanuel35

I would like to do a PCB review too for the same above. This time I would prefer to do it on a private chat rather than post it on a public domain. Can we arrange this please?

Thanks and regards