TPS2546: Load detection - Power wake: set/reset time

Hi Adam

Thank your reply, but I would like to know the load detect set time for power wake. Could you tell me the specific value?

As the table, load detect set time - non power wake is among 140~275ms. However, load detect set time - power wake?

Thank you!!

Hi Eddie,

Unfortunately we do not have a parameter for this within the datasheet. 

Hi Adam

However, our customers meet an issue and hope to know the parameter(load detection set time -power wake). Does anyway help us to know the value??

Thank you

Hi Eddie,

What is the issue the customer is seeing?

Hi Adam

Customer sets to 0011 and wanna know the set time as the current spike over the 67mA which is the threshold  for load detect power wake.

You could check the below waveform

Hello,

The purpose of the load detection circuit is to indicate to the system when a load has been attached which would pull a constant current. This is just an in rush current spike which is not enough to indicate that a load has been detected. 

We do not have the timing for load detection set time -power wake is not available 

Hi Adam

Why could we not measure the the set time? It could be more helpful and clear for user.

Thank you

Hi Eddie,

I can try to measure this but I will not have a chance to test this until middle of next week. Will update you with my results then 

Hi Adam

Thank you! But it is too late for the result. Could you pull-in the timing?

Hi Eddie,

Unfortunately no. I have previous commitments that I need to work on beforehand. If the customer needs it beforehand, then they can actually conduct the test themselves. Just connect a light load on the VBUS pin, and see at what point the STATUS pin goes low. 

Hi Adam

So could you make a specific dead line for the measurement? How about before 5/27?  I could tell to customer.

Thank you

Hi Eddie,

Adam is out of office currently, he should be able to get back to you next week. Could you please have customer test on their board as Adam described in the meantime, it should be too difficult to do the testing?

Thank you,

Hari

Dear Hari

I also would like to measure the parameter by myself but our country recently outbreak COVID-19. Therefore, we could not visit our customer to debug and should stay home to work.

Thank you

Eddie

Hi Adam

Thank your help. Actually, I would like to know the detection time not STATUS transform. How long will I_VBUS trigger the STATUS as I_VBUS over the threshold?

You could refer the above waveforms from customer that descript the duration over the threshold and cause STATUS to change its state.

Thank you

Hi Eddie,

I am not sure I understand your question. It will take about 200us of I_VBUS over the threshold before the STATUS pin is asserted. The STATUS pin will remain asserted for as long as the current on VBUS is above the threshold. 

Hi Adam

If your measurement is that I_VBUS should take 200us over the threshold before the STATUS pin changing. However, the below picture seems not matching your result. There is a periodical  current spike which over threshold but less than the 200us why is the STATUS pin asserted?

Geen: I_VBUS; Purple: STATUS;  3.85us over the threshold; I_VBUS Max: 288mA, STATUS: 0V

I would like to know what is the minimum duration of I_VBUS over threshold causing STATUS pin changing??

In your waveform, the I_VBUS is near constant value but my customer met the problem is current surge.

Thank you

Hi Eddie,

You can see that the STATUS pin is already low when the current spike is seen. So something is occurring before the current spike in this measurement. The current spike shown in the measurement is not causing the STATUS pin to go low

Eddie Yeh said:

In your waveform, the I_VBUS is near constant value but my customer met the problem is current surge.

Is this current surge being seen when no adapter is connected? If so, then that is the problem. Why are their transient current spikes without any device connected. If this current surge is from a connected device, then wouldn't the system want to know that a device has been connected? 

Hi Adam

Please, check the waveform.  Fig1. Green is Iout and yellow is STATUS. TPS2546 sets to 0011.

After 2.06s of the system into S5, STATUS pin change to low. 

Why is each current spike duration below 200us which still caused STATUS keep in Low?

Hi Eddie,

You can see in the electrical characteristics for the power wake mode, that it has a typical reset time of 15 seconds.  So the STATUS pin could eventually be going back High, but it does not show in your capture.