BQ25890H: Any way to disable part

Is there some min current that would still allow I2C communication even without a battery?

Minimum current regulation using ILIM pin is 500mA.

If you leave D+/D- lines floating, the IC will detect an unknown adapter and set IINDPM to 500mA.

So I floated ILIM by removing the resistor I have connected to it.  I'm still able to communicate over I2C.  I plugged in a battery and REG0B indicated it was fast charging.  Am I missing a step somewhere?

Thank you

Eric,

What is the voltage at SYS with VBUS only applied?  To what voltage are your D+/D- lines pulled up?

SYS is about 1V. DP/DM are shorted to each other as recommended by TI. There is another BQ25890H in the system that handles talking over USB.

Eric,

With D+=D- and ILIM pin floated, input current limit (IINDPM) is set to 3A. What is the voltage at VBUS? Has VINDPM clamped input current below 3A due to load on SYS?

Also I got my fake battery emulator to work so I can see now that it does not charge the battery despite what I saw reported.

I made a lot of progress with this but I'm seeing some weird behavior on startup.  I have my second charger's Ilim floating so he shouldn't be drawing any current.  Then I wrote some software to watch for a power good event.  When I see it I split the available current between the two chargers.  

Now I just removed that portion of the code so all I have is my main charger with ilim grounded and the second charger with it's ilim floating.  Only the main charger is connected to DP/DM lines.  So what happens is I connect my device to a laptop and there is a short series of very high current draws peaking at about 1.5A.  It will eventually settle at 500mA.  Is this something you have observed before?  Is it expected behavior?  What happens is on some ports or some laptops I get kicked off the bus and I assume it is from misbehaving with my current draw.

---edit ---

I see that disabling auto detect for the main charger stops this from happening.

Thank you

Eric,

Can you attach your schematic? 

The charger should not draw more than average current than the IINDPM setting.

Can I send it to you privately again?

sent in a PM

also right now I removed resistors 520 and 546 which float Ilim and DP/DM on charger 2.

Just a little more evidence to share. This does not happen on my docking station USB ports. Those work fine. Only on my laptop. These have something called Dell power share, I wonder if it's confusing the detect mechanism.

The charger should recognize the laptop port as either SDP (100mA) or CDP (900mA). I haven't seen peaks like that. What is the time scale on the scope plot? What is your load on SYS of main charger? What is the voltage measurement at VBUS of main charger when this happens? Is the charger hitting VINDPM? Can I get a scope shot of VBUS, SYS, IBUS, ISYS? Just to confirm, this is will battery not connected, yes?

Time scale was 2.0ms. You're right the charger recognizes those laptop ports at CDP but it will not connect. I see traffic on the USB bus and then the laptop takes power away from us. This happens in a cycle forever. I also added a 1k resistor on main charger Ilim to reduce the current spikes I showed you. Even with that change though it still did not connect.

However I noticed that if I had auto detection disabled my device will connect to USB right away, no issues. As a work around I put in a timer that disables auto detection after a successful detection for 5 seconds. In that case my device is kicked off the bus but the second time around it connects. Not sure what the root cause of that is.

The screenshot was with both batteries connected, one each to charger 1 and charger 2. The system cannot run from laptop power alone. I'll work on those other captures for you. I can get VBUS, SYS, IBUS, but not ISYS at least not without a lot of effort :)

Thanks for the help so far I appreciate it.