PTH08T250W: Using two modules in parallel and for current control

Hi Tahar,

What I was thinking of is controlling the load current by driving the 'Vo adj' with an op-amp.

Mark

Hello Mark, 

I am not aware of this method been tried before in the PTH08T250W. The Vo Adjust function of the  PTH08T250W device is similar PTH12040W. 

Thanks! 

Tahar

Hi Tahar,

Looking at TIDA-00582 schematic. Switch S1 can be used to adjust Rset. Is it safe for the PTH08T250W to switch S1 while the power is on?

Mark

Hello Mark, 

That can be done, but depends how aggressive the change is, you may run into stability issues. As I mentioned above, I am not aware of this method been tested and proven with this device. 

Why you do not want to use the device per the TIDA mentioned above? That is the recommended method to paralleling these modules for high current of upto 100A application. Configuring a PTH08T250W as a master and each additional module as a slave allows start-up and transient conditions to be controlled by a single module.

Thanks! 

Tahar 

Hi Tahar,

The application is to drive a laser diode. 100A is needed to get maximum output power out of the particular laser diode model. The diode voltage for maximum output power is around 2 volts but exact value is device and temperature dependent. That is the reason why output current control is necessary.

Do know if it would be possible to obtain a loaner TIDA?

Mark

Hello Mark, 

I checked the TIDA is not orderable, we only provide the report and the supporting documents as in the web. 

Can you show me a high level SCH of what you are trying achieve, I can review it and give further feedback? Also you mentioned a design with similar topology using pth1204w, can you share if that possible as well? 

Thanks! 

Tahar

Hi Tahar,

This is the link to the 3rd party laser driver.

https://analogmodules.com/wp-content/uploads/2017/12/787.pdf

From looking at the board, they are driving the 'Vo adj' with an op-amp.

Below is the diagram of what I am trying to do. I hope it is legible.

Mark

Hi Tahar,

I got a positive news. The TI's spice PTH08T250W model - PTH08T250WECU_TRANS - does respond as I hoped it would to driving the 'Vo adj' pin. I applied a ramp with rise time of 0.5 ms to the 'Vo adj' pin and the Vo responded as expected within 1 ms. See attached pictures.

Mark

Hi Tahar,

I cannot get PTH08T250W master/slave configuration to work in PSpice. Do you know if this has been successfully attempted? What are the tricks?

Mark 

Hi Mark, 

Great, if the PSPCIE mode provide a stable operation, then most likely this will behave as such in hardware as well. 

Thanks 

Tahar

Hi Mark, 

The PSIPCE mode does not have the share feature, I tried and does not support two. I run some transients and is not doing what need to be done without Ishare.  

Are you planning to do a simple  prototype board to do further testing, because I think what you have so far is promising.   

Thanks! 

Tahar