UCC28180: UCC28180 is question about ISENSE resistor.

Hi Bob,

I am reaching out this question with design team. I will answer you asap.

thanks.

Dear David Huang33,

Thank you very much for reply.

May I ask add question?

I worry about the pin3 (ISENSE) and pin 1 (GND) Diode speed and I am add asking questions.

(Datasheet)
There is a description to insert a diode between pin 3 (ISENSE) and pin 1 (GND).

(Question2)
As long as Vf falls within the range specified in the application note, there is no problem with Schottky, high-speed D, or commercial D？

Best regard.
Bob Lee.

Hi Bob,

For the clamped diode, at 8.3.14 paragraph on the datasheet there is explain on how to choose the diode.

No problem with Schottky, but please keep in mind that VF should be between 0.438V-1.1V.

Dear David Huang33,

Thank you very much for Quickly answer.
May I ask add quwstion about diode?

(Question3)
What is the purpose of inserting a diode?

The customer is in mass production.
I ask to support urgent about ISENSE resistance value and Question3.

Best regard.
Bob.

Hi Bob,

the diode is used to protect the PFC stage during the condition like surge test or lighting that has very high inrush current through Rsense.

if the inrush current is very high and the Isense pin voltage higher than 1.1V, The controller will output high at this condition. This may cause failure on PFC stage, so in order to avoid this condition, the diode is added to clamp the Isense pin voltage to be less than 1.1V. And the the VF of the diode should be higher than 0.438V which is the ocp threshold to avoid influence of ocp function.

Dear David Huang33,

Thank you very much for quickly answer.

Please continue to support us.

（Question）
If this resistance value is set to 100Ω or 330Ω, etc.
Are there any problems?

Best regard.
Bob Lee.

Dear David Huang33,

How is the progress?
I would like to answer my customer by Japan time 8/8.

（Question）
If this resistance value is set to 100Ω or 330Ω, etc.
Are there any problems?

Please continue to support us.

Best regard.
Bob Lee.

Dear David Huang33,

Thank you very much for reply.
I reply my customer your answer.

I will feedback my customer situation.

Best regard.
Bob Lee.

Dear David Huang33,

Thank you very much for reply.

If I have any questions, I will post a new one.
Please give me support.

Best regard.
Bob Lee.