TUSB4020BI: Downstream port power over current switching

Hi Ted,

Is the upstream port of the hub connected / active when this occurs?

Regards,
JMMN

Same result if connected the MacBook/powered hub or any adaptor. On the evm I have the +5 from the input jumpered over to the external 5V so it can be a self powered hub. Works well, just doesn't trip the overload port. The 2561 collapses the voltage but maintains the current.

The trip does work when Automode is off i think?? I want automode so that it can be a BC(divider) charging hub when connected to an adaptor or DCP/CDP when connected to a hub

Hi Ted,

FYI, if AUTOMODE is enabled, CDP is disabled.   I tested regular TUSB4020B and charging mode and I saw that when OVERCURz is asserted low, PWRON is disabled.  However, once the OVERCURz is not asserted, PWRON will be re-enabled.  Does this match the behavior you are seeing?

Regards,

JMMN

well, made some progress. Overcurrent downstream power management only seems to work when VBus is tied high and connected to a CDP which means no AutoMode (no BC Divider mode).  Even with automode disabled, downstream port control doesn't work with VBus low.

I'd like to have downstream port management work when connected to an Adaptor.  Is there a configuration that does that?

JMMN, not sure what PWRON is?

Hi Ted,

I just sent you a friend request, can you accept it and send me your schematic directly (it won't be posted online).

I meant to say PWRCTL, not PWRON.

Thanks,
JMMN

JMMN, at this point I am using the TI evm, TUSB4020PHPEVM REV A. Figured out today that it doesn't do Data or Power switching when VBUS <5 (which puts it in DCP mode). So, I suppose I'll live without downstream port power control because I need data.

Any way to set it up such that it won't enumerate more current than the upstream port/adaptor indicates?

thanks, ted

HI Ted,

Unfortunately no, there is no way for the TUSB4020B to modify its behavior based on the reported current consumption of devices. I took at look through your EEPROM file and i noticed that you had the ports marked as non-removable: "07 0C 00001111 'ports removable" which could impact the power control.

Regards,
JMMN

Yes, I caught that error eventually and changed register 07H to 83H.

Now believe the TUSB2040 will not meet my requirements.

I was just looking at the TPS2540 and it is very close.  If I could figure out a way for it to automatically select one current limit for SDP and a higher one for CDP/DCP it would work.

Is that possible?

If not, is there a TI controller/switch that can adjust current limit automatically?

thank you, ted

Hi Ted,

It sounds like the TPS2546 may be a better fit for your application than the TPS2540 or a hub.

Regards,

JMMN

So, if I connect a tusb4020 evm to a macbook pro USB port that is theoretically a CDP 1.5 and then plug an iPhone into each TUSB port that enumerates as DCP 1.5 is that considered USB Compliant even though I have each port limited (via TPS2561) to 1.25 A.

Is it up to each iPhone to limit its current draw if VBus droops?

Plugged into the Laptop the current to each phone is .75 A and the VBus voltage is 4.4 V.  VBus input is 4.6 V which indicate the upstream port is drooping under the load.

Plugged into a 2.4 A adaptor, each phone pegs at 1.2 A with VBus at 4.6 V.  VBus input is 4.9 V.  shows the TPS2561 working properly.

switch settings S8 - S1: 0 0 0 1 0 0 1 1

Is this a compliant configuration?

thanks, ted

still looking for best solution