BQ24618: BQ24618 Board Not Running

Hello,

I will get back to you by next week.

Thanks,

Mike Emanuel

Hello,

Can you please obtain a waveform of the input voltage, PH voltage, SRN voltage, and output current when this is happening (preferably all on the same plot)? Also, can you confirm the SRN voltage at the pin?

Thanks,

Mike Emanuel

BQ24618Board_AdditionalInfo.pdf

Here are the plots you requested. There is no measurable current into the battery. There is about 4mA of board current.

Is there any chance the PCM on the battery is affecting anything? I would not think so. I would assume it protects against over charge and under discharge. I lowered the charge current to 1.5A and tried 2 different batteries and still nothing.

If there is anything else, let me know.

Thanks, Tim.

Mike,

I am not sure what the battery supplier is using.

I tried one at 1.5A without the PCM and it acted the same way. So maybe that is not it. (Shoot!)

Thanks, Tim.

Dear Tim,

Can you probe the REGN, VREF, TS, VCC, input voltage, ACSET, ISET1, ISET2, and CE with a multimeter?

Thanks,

Mike Emanuel

Mike,

REGN = 5.971V, VREF = 3.292V, TS = 1.657V, VCC = 12.08V, VIN = 12.23V, ACSET = 0.815, ISET1 = 0.298, ISET2 = 0.106V, CE = 3.292V.

Thanks, Tim.

Dear Tim,

Are you able to send your layout? Those voltages seems good, what is the SRN DC voltage when this happens?

Thanks,

Mike Emanuel

Mike,

Okay. It is a 2 layer board

.BQ24618Board_Layout.pdf

Thanks, Tim.

Oops. Forgot to answer other question. SRN is at 3.774V. 

Dear Tim,

I need some additional time to review this layout and will get back to you next week.

Thanks,

Mike Emanuel

Dear Tim,

What type of capacitors are you using? The datasheet footprint seems to suggest they are polarized, is this the case?

Thanks,

Mike Emanuel

Mike,

These are just ceramic caps. Non-polarized.

Thanks, Tim.

Dear Tim,

I will go through the layout guidelines as follows:

1. The input capacitors C9 and C4 both need to be as close as possible to the MOSFET supply and ground connections.

2. The IC needs to be placed as close as possible to the switching MOSFET gate terminals for a clean gate drive.

5. The output capacitor needs to be placed next to the sense resistor output.

7. Please make sure that analog ground and power ground are tied together as described in the layout guidelines.

8. Is the thermal pad connected to the PCB ground? I cannot tell from the layout provided, but this is critical.

9. The VREF capacitor could be placed closer to the IC.

Thanks,

Mike Emanuel

Mike,

Is your conclusion that the schematic is okay, the parts are okay, it is just the layout that is causing the problems? End of story?

(And yes the pad is grounded.)

Thanks, Tim.

Mike,

I doubt we will ever use BATFET.

I used a 10uH inductor instead of a smaller 6.8uH inductor, since we had these in stock. Could that be an issue?

Thanks, Tim.