TPS92630-Q1: Open load fault detection issue

Hello TI Team, Could you provide feedback? 

Hi

i need the wave form of Vin Vou fault pin.

Hi Frank,

Please see below capture, if you need more information, please let me know, thank you.

Hi

I think the issue is due to the LED model, if you have to remove R4 R5 R6 to make sure the device is working normally.

Why TPS92630 still detected open load fault if I set PWM 100% output when Vin < 14V? 

A:Beacuse of the resistor r4 r5 r6, the device work in dropout so the device will detect open issue.

Is it possible to use TPS92630 to do constant voltage control?

A:It's a constant current device.

So I think you have to deal with the LED board or you have to choose some LDO or buck device.

Could you tell me why the LED board is like this, and what's your consider of using r6 and r5r4.

Hi Frank,

Thank you for your replied, actually, the LED module was supplied by 3rd party and the car OEM did not want to change the resistors value due to this LED module is a share part in car different platform, other ECU control it with constant voltage.

one more question, I found LED will blinking under certain voltage if met open load fault, does the fault detection has hysteresis mechanism? 

Hi 

Do you mind to upload the video again, I can't see any picture from it.

Hi Frank,

I don't know why upload video always failed, but you may try to reach below path:

https://drive.google.com/open?id=1cJrjnQ3teuPW-A0aOuSwPYXApmN4vYSn

Hi

Do you have control on other pwm pin.

if you give no feedback i will close this topic.

hi Frank, I didn't understand what you mean, please explain more clearly and do not use short words to reply the questions, at least the whom don't get your point is me...thank you so much.

Hi Frank,

Sorry, I think the question not yet been solved, did you watch the video which I uploaded, what's your comments and suggestion? my local FAE told me to ask the question on e2e forum and will get the correct and prompt response, seems he was wrong and make me disappoint as well.

.

Hi Sony ,

Sorry for the mistake, i open this topic from the morning, so i don't see your update.

I see you use two channel of TPS92630-q1 but you only offer one pwm input,so i ask you do you have any control on other pwm input pin

Hi Frank,

Yes, I did have control another pin by PWM at the same time, the freq / duty were the same; we have a self-test mechanisim which is to turn on both channels at the same time for a while.

Could you help me to capture the waveform of PWM pin(if two pwm share the same freq / duty and phase just catch one), output 1 , output 2, and the fault pin. And i want to confirm one thing：whether the Vin is a constant voltage source or not. 

Hi Frank,

PWM1 and PWM2 were controlled seperately but output by the same PWM setting when ECU power up. I has capture waveform as below, the VIN is 13V, PWM is 100%, I'll measure IOUT1 and remove PWM2 later, thank you.

Hi Frank,

I had captured more waveform as attached, measured under DC14V, 13V, 13.5V, 12.5V and 12V, for your reference.

capture.zip

Hi Frank,

Do you have any update? Another week has passed...thank you.

Hi Sony,

I have tested your setting in the EVM (the load as you set), but I can't recurrent the phonomen.Do you mind send a prototype to me for futher testing.

Hi Frank,

Did you test with equivalent resistance as 267 ohms and two LEDs in series? PWM freq is set to 200Hz, duty cycle is 100% and output both channels at the same time, could you try it again?

Hi Snoy,

I can't recurrent the phenomenon as your load condition, it can normally works in our EVM.

i notice the signal LED short resistor R140 & R149's value may have some issue, i recommend you to set R140 50K and R149 10K (also for the R141 & R137)

Hi Frank,

Thank you for your response, did you mean I should exchange the resistance of R140 and R139? Could you also let me know why you suggest to do like this? Thank you so much.

yes,

the divided resistor are used for single LED short detect, your set has some issue and it will trigger fault detect.

Hi Frank,

After swapped those resistors as you suggested, the issues still happened, FAULT pin still goes low; in facts, we did not monitor the FAULT_S pin, only FAULT pin.

Hi Snoy,

In your schematic I see the fault and fault_s connect together, do you mean you don't connect them in fact.

I have built a  load as your offer. But I don't use bead and the output cap (c133 c217,c132 c145) i use is 1nf cap. 

You can try to remove the beat and use 1nf output cap as I set.

Frank Qiu said:

In your schematic I see the fault and fault_s connect together, do you mean you don't connect them in fact.

Hi Frank,

Yes, we did not connect fault and fault_s pins together in the circuits, I'll follow your suggestion to try again and feedback to you then, thank you.

ok