Question for LTC3309A application

Hello,

There could be a few reasons why the load regulation might not be as good. Small 0402 or 0201 (better) VIN to AGND and a VIN to PGND should be placed as close to the pins as posible. Please see the Low EMI PCB Layout section and pin discriptions in the LTC3309A datasheet for more information on this. Is the FB sensed close to the load? Where is the output measured? Is there a kelvin connection to the ouput?

Thanks for your answer.

Below is my layout. I use one line to connect the IC's AGND with peripheral devices. The small 0402 capcitor is a little far from my Vin pin. Would this cause my load regulation be worse than ideal design?

Could you offer me the Design materials for me（PCB/layout or PDF）

0602.610-DC2745A_REV06_GERBER.zip

Hello,

Attached is a zip file containing the Gerber files for the layout. We do have pdf files as well but I could not load them at this time. Maybe it was to big for both on a single reply.

The attached layout uses a 4 layer board with layer 2 a solid GND plane. There are VIN to AGND and VIN to PGND 0201 caps very close to the IC. AGND is a wider trace. AGND and PGND only connect at a single point near the output capacitor.

I hope this helps.

I did forget to answer you question. We did find that having the decoupling caps out farther did make an effect on the regulation. Having them as close as possible will help.

1172.DC2745A-6-CHECK PLOTS.zip

I also included a zip file containing the layout in pdf files.

Thanks for your kindly reply. 

I will check it and do some test.

May I ask when will those desige materials realse in the ADI Official website

Hello,

We are in the process of releasing it now. We are just doing the final edits on the demo manual. After that is signed off I still believe the process to release it on the web is still 2-3 weeks. My guestimation is about 3-5 weeks.

Got it.

Thanks for you help.

Dear Marty:

I have done some tests on my board.

I'll find the FB voltage dropped(FB voltage will drop to 0.47V while the output current is about 6A) while the load becomes heavier. 

I have reviewed the Datasheet and find the LTC3309A is the 1st generation Silent Switch technology architecture. So the Caps should place symmetrical with Vin and Vout. 

In the meanwhile, the LTC3309A on my board can't startup with Heavy load. And due to the SS pin may be design inside the IC, so I can't change the SS cap to set the startup current.

Could you please give me some advice?

Hello, What are you using for a load? Many electronic loads look like a short at startup. We have not seen any issues with the LTC3309A starting up into full load, 6A.