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How to calculate the TILN inductances for the CC2590

Yoo Hsiu Yeh
Intellectual 425 points
Other Parts Discussed in Thread: CC2640, CC2590

Hi all,

I am creating a design that uses the CC2640 with the CC2590 gain amplifier. I have been given two different reference schematics for the CC2590:

- the CC2541-CC2590EM schematic here: www.ti.com/.../swrr116

- the CC2590 datasheet: 

In the CC2590 datasheet, there are two transmission line inductors,

- 0.87nH on AVDD_PA2 (pin 10), Length=40mil, width=8mil

- 1.54nH on AVDD_LNA (pin 13), length = 100mil, width = 8mil.  These were calculated for a 1.6mm thick 4-layer PCB.

In the CC2541-CC2590EM schematic, we have

- 5.1nH chip inductor on AVDD_PA2 (pin 10).

- TLIN inductor of unknown value on AVDD_LNA (pin 13). Measuring the gerber file gives approx 200mils length, and 8mils width.  So the length is about twice what is recommended in the datasheet.  This is also for a 1.6mm thick 4-layer PCB.

So I have two questions:

1. Are the two circuits equal?

2. If I have a 1mm 4-layer PCB, how would I recalculate the values so the inductances are the same?

Thank you very much for your reply.

  • 0
    TI__Mastermind 18780 points

    Hi,

    The CC2590 performance is sensitive for layout changes. I would recommend that you follow the reference design for the CC2590 part closely, and keep tha stack-up between the top layer and the GND layer underneath as in the reference design. Then  change the stack-up for layer 3 and the bottom layer to fit your PCB. This will give the lowest risk to get good performance with mininmum tuning/debugging.