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Posts: 2
Registered: ‎04-17-2017
Accepted Solution

Proper antenna load resistance Si4012

Hi,

 

document https://www.silabs.com/documents/public/data-sheets/Si4012.pdf, page 5:

 

>>Therefore the antenna load resistance in parallel with the Si4012 differential output resistance should equal 600 

 

document https://www.silabs.com/documents/public/application-notes/AN639.pdf, page 12:

 

>>For the Si4010 chip configured for the maximum value of PA bias current, the load resistance at which clipping occurs is RIN ≈ 500 Ω. As a result, this value is often stated as being the optimal load resistance for the Si4010 chip, and is usually the design target for the input impedance of a loop antenna.

 

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For the Si4012 chip, should I swap the 500 Ω with 600 Ω in Equation 26. ?

Posts: 88
Registered: ‎02-25-2014

Re: Proper antenna load resistance Si4012

The optimum load impedance is: 

~600 ohms for MSOP, and

~500 ohms for SOIC package of Si401x.

 

However, Silicon Labs recommends to have the differential input impedance of the loop antenna slightly smaller than these values above, in order to avoid harmonic issues. So, the design target for the loop antenna input impedance would be around 400-500 ohms (for SOIC and MSOP packages, respectively).