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CC1125: Will the load impedance value 57 +j4 ohms on pin 17 (PA) will remain the same for 220-222MHz application

Jonathan Geronga
Expert 7930 points
Part Number: CC1125
Other Parts Discussed in Thread: CC1200

Hi Team,

We have a customer with the following inquiry below:

Our customer is currently using CC1125 for their 217-220MHz half-duplex radio and the load impedance values for pin 17 is 57 +j4 ohms according to this e2e post below:


Will the load impedance values on the pin 17 (PA) remain the same if they are switching to 220-222MHz application?
They can change the passive LC filter on the receiver side to accommodate the 220-22MHz application.

Please confirm if this is possible.

Thanks!

Jonathan

  • 0
    TI__Guru**** 317180 points

    As far as I know we haven't done any testing in the wanted band. 57+j4 is from the ref design we made for 169 MHz. 220 Mhz is fairly far away from 169 MHz if you calculate in percent so I would assume that the load has to be adjusted. 

    One way to do it is to plot the impedances in the post you referred to and see which impedance 220 MHz end up with if you follow the line between the different data points. A different method would be to scale the network with 169/220 as a starting point but it could be that some different filtering is required dependent on the regulations for the band they want to use. 

    Since we haven't tested this, the customer has to do testing and tune the network accordingly.

    Also look at https://e2e.ti.com/support/wireless-connectivity/sub-1-ghz/f/156/t/556722?CC1200-matching-circuit-for-220MHz

  • 0 in reply to TER
    TI__Expert 7930 points

    Hi TER,

    Thank you for your response. We already informed this to our customer and here's their response:

    They already have an FCC approved radio which is operating in the 217-220 MHz range & the PA (pin 17) load impedance is 57+j4 ohms.
    They said that they can change the pre-select filter which connects to the LNA pins 19 & 20 from 217-220MHz to 220-222MHz. 
    Do they still have to change to CC1200 or will CC1125 work?

    Thanks!

    Jonathan

  • 0 in reply to Jonathan Geronga
    TI__Guru**** 317180 points

    CC1125 and CC1200 covers the same frequency range.

    If they have a radio that operate in the 217-220 MHz range and are happy with the performance they should test this in the 220-222 MHz range.