[ TPS60231 ] LED Open Detection

Hi,

The customer uses 2 Led's and want to detect if one of them fail, right?
Can you provide the part number of the led's?
What about the values in the table at 20% duty cycle. (red marked)
Are they measured right?

In general the detection should work as long as there is enough margin.

Regards,
Michael

Hi Mike,Thank you for your reply.

This is for production line to check LED connecter is plugged into board correctly or not.
This means if LED is open, both two channels are open.

Yes, they can measure the current as table above, can you comment from design perspective that the current customer measuring is reasonable or not for each case (w/ LED, w/o LED)?

Also, do you think this current can be used for LED open detection purpose at production line?
What I’m concerned are this current may vary over different lot and/or other condition.
If this current difference is always the case, it works fine, though.

Thanks,

Ken

Hi Mike,

Sorry for rushing you, but it's really appreciated, if you can reply as soon as possible. Since customer is really close to their production start, so they need information soon.

Please contact to me directly, if you need further info. from my side.

tanaka-k(at)clv.macnica.co.jp

Thanks,

Ken

Hi Ken,

I understand that customer needs information asap.

I don't have a EVM in my lab since this is an older device.
It will take some days to get the Material and perform some tests.

Do the Led's have some variations?

Thanks & Regards,
Michael

Hi Michael,

Thank you for your support!
Yes, according to customer, Vf of their LED has +/-10% variation. This could cause the current variation as well, correct?

Let me try to summarize what I would like to make sure.

1: When no LED connected to TPS60231(Open), 5V supply current is getting increased.(see table above). Can you explain why this happen? and is this expected behavior?

2: According to customer, 5V supply current for the condition of No LED, 20% duty is around 26mA while 7mA with LED. Are these number reasonable? Do you have any ideas how much variation does this value have?

Please let me know, if you have any questions. tanaka-k(at)clv.macnica.co.jp

Regards,

Ken

Hi Michael,
Sorry for rushing you, but it's really appreciated if you have any update on this discussion.
Thanks,Ken

Hi Ken,

Today i received the EVM and performed the first measurement.

These are the values i got: (5Vin)

Duty [ % ]	With LED	No LED (Open)
0	<0.01	<0.01
20	8	4
100	40	4

This results matches with the numbers i expected.

How does the input current measurement setup looks like at the customer board ?

Maybe there is something wrong.

Which Frequency do they use for the dimming?

Regards,

Michael

Hi Mike,

Thank you for your support!! I understood that  what you are seeing is something different than customer observation. I will share your result with customer and confirm PWM freq. Can you send an e-mail to me? I can share the business background with you.

Thanks,

Ken