TPS92200: Is there any way to drive 2 LED strings by TPS92200?

Hi Kazuya,

May I understand what is the voltage and current for the two LEDs? What is the input voltage?

BR,

Steven

Hi Steven,

Thank you very much for your reply kindly.

Vin=12V, Vo= LED Vf * 2pcs in series = 7V (3.5V * 2, Daylight and lamp color are similar Vf), Io = 900mA.

If you need more information, please let me know?

Thank you again and best regards,
Kazuya.  

Hi Steven,

Thank you very much for your prompt reply.

If LED path is changed when TPS92200 is not active, can PMOS FET be inserted between LED anode side and output capacitor

(= inductor output side)?

Thank you again and best regards,
Kazuya  

Hi Kazuya,

If PMOS is connected in such a way for TPS92200, the source of the PMOS will be floating and driving it will be complex.

For TPS922053, the source of the PMOS is connected to Vin, which makes the PMOS easier to drive.

Best Regards,

Steven

Hi Marek,

Do you have the same question as Kazuya? Is there anything I can help with?

BR,

Steven

Hi Steven, Marek,

Thank you very much for your supports.

Steven,

I think source voltage of PMOS FET would be fixed to drain voltage (=LED anode voltage) + 0.1V~0.2V.
So the source voltage should be not floating.
Is my understanding correct?

Marek,

I want your comment too. Could you please give me your help?

Thank you again and best regards,
Kazuya.  

Hi Steve,

I'm sorry that I forgot to write the following my comment.

The customer needs 900mA LED current and doesn't need high speed turning on/off time.
Also they prefer lower cost device. 
So they want to use TPS92200.

Thank you very much and best regards,
Kazuya. 

Hi Kazuya,

Kazuya Nakai59 said:

I think source voltage of PMOS FET would be fixed to drain voltage (=LED anode voltage) + 0.1V~0.2V.

For the first time before you turn on any LED strings, the source of the PMOS is floating and is difficult to drive.

BR,

Steven

Hi Steven,

Could I ask you an additional question?

How about NMOSFET case? Is it difficult to drive 2 LED strings in time division by NMOSFET inserting between cathode of each LED strings and TPS92200 low side sense resistor (RSENSE)?   

Hi Kazuya,

I am currently out of office. I will reply to you before tomorrow.

BR,

Steven

Hi Steven,

The customer wants use TPS92200 and it is very helpful for them if you give any schematic to to drive 2 LED strings in time division. 

Could you please give me your reply?

Thank you very much and best regards,
Kazuya.

Hi Kazuya,

Sorry for the delay.

I think it may be possible to do so with N-MOSFET. You should pay attention to the "LED open load" protection feature of TPS92200.

Kazuya Nakai59 said:

Is it difficult to drive 2 LED strings in time division by NMOSFET inserting between cathode of each LED strings and TPS92200 low side sense resistor (RSENSE)? 

Currently I have not seen similar application before, but I think your description may be a feasible way to do so.

BR,

Steven

Hi Steven,

Thank you for your reply.

I understood that you have not seen similar application before.
The attached schematic is my understanding. Is this same as your thought?

Thank you again and best regards,
Kazuya.

2LED_drive_schematic_20230907.pdf

Hi Kazuya,

Yes. The circuit connection is the same as my thought.

Best Regards,

Steven

Hi Steven,

Thank you for your reply.

Could I ask you a question about TPS922052/3/4/5 schematic you showed at the beginning part of this thread?

Q, Has this schematic been verified to work?
     If you have it, could you please give me the test conditions and each part parameter?

Thank you again and best regards,
Kazuya.

Hi Kazuya,

This schematic is verified from theory only at this moment. If you do have a need, I can verify it on the EVM.

BR,

Steven