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PA ramp

Sergey Gerasimenko
Intellectual 600 points
Other Parts Discussed in Thread: CC1310

HI, we need to control PA ramping in CC1310.

In July 2017 SVS wrote to a user:

PA ramping is configured in bits 15:8 of the value written at address 0x6088 (configured by the override). Bits 15:13 configure the PA trim time increment in steps of (8+4*2^PaTrimTime)/12 [us]. Bits 12:8 configure the the PA trim step size (zero is illegal, lower this value longer is the ramp time).

In addition, ramp time can also be setup by changing the value for bits 15:8 at address 0x608C (default is HW_REG_OVERRIDE(0x608C,0x8213)). Bits 15:13 configure the PA ramp IB  time increment in steps of (8+4*2^PA ramp IB  time )/12 [us]. Bits 12:8 configure the the PA ramp IB step size (zero is illegal, lower this value, longer is the ramp time).

Please refer to the following wiki for ramp settings used at higher data rates.

http://processors.wiki.ti.com/index.php/Settings_for_Different_PHY%27s

Regards,

SVS
My questions are:
1. What is "IB" in the answer above when the register  0x608C is referenced?
2. How exactly the registers 0x608C and 0x6088 work together to define PA ramp time?  In the link above to the settings for different PHY there are two examples:

  1. "PA ramping. Set HW_REG_OVERRIDE(0x6088,0x1024) and HW_REG_OVERRIDE(0x608C,0x0813). This gives a PA ramp time of approximately 5 us."   I can't figure out how this number of "5 us" was derived using the explanation given by SVS.
  2. "Set HW_REG_OVERRIDE(0x6088,0x6119) and HW_REG_OVERRIDE(0x608C,0x8113). This gives a PA ramp time of approximately 100 us "  The same - how did it result in 100 us.

Can you please explain?

Thank you,

Sergey

  
  • 0
    TI__Guru**** 317180 points
    A question on the side: Why do you want to alter the PA ramping?
  • 0 in reply to TER
    Intellectual 600 points

    The main reason is that we are seeing a huge amount of wide-band noise in Transmit in our design that uses a CC1310 and an external PA. The RF people in my company asked a question of how quickly we ramp the power up and down, hence is the question.

    The second reason is that our modem supports a wide range of link rates, starting from 19.2 kbps and up to 500 kbps, and I would like to make sure that the ramping time is set properly for each link rate.

    The last reason is to understand the product. 

    Sergey

  • 0 in reply to Sergey Gerasimenko
    TI__Guru**** 317180 points
    IB:
    tpower consist of the following fields:
    Bit 0..5: IB: Value to write to the IB field
    Bit 6..7 GC: Value to write to the GC field
    Bit 8: boost: Value of boost bit in synth
    Bit 9..15: tempCoeff: Temperature coefficient for IB. 0: No temperature compensation

    Where IB is the bias current to the PA and GC is a gain factor.

    Wide band noise:
    Do you have a plot showing the spectrum from CC1310 alone and after the FEM highlighting the issue you are seeing?

    Ramping time:
    If using the settings from SmartRF Studio the ramping is scaled with datarate
  • 0 in reply to TER
    Intellectual 600 points

    Thanks for clarification. 

    After upgrading the project to include the latest RF patches the noise went away.

    And if the ramping is scaled with data rate, we should be ok.