This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Buck converter for RF microwave amplifiers

Other Parts Discussed in Thread: LM76005, LM73605, LM73606, LM61460

Hi everyone,

I was reading this: https://www.ti.com/lit/an/snva593/snva593.pdf and i thought that it would really help battery life in my case too.

I am looking for a buck converter to use with some RF power amplifiers.

There are two kinds of PAs, those that work at 2.4GHz & those that work at 5.8GHz.

There are 6 PAs powered by the same source, have a voltage range of 6-16V and have quiescent currents 40mA & 80mA (2.4GHz & 5.8GHz respectively).

I used to power them directly from a battery pack but since their current peaks of 6A go above the specs of the battery pack which is 4.5A max i would like to use a buck converter after the battery in order to drop those current peaks to within the battery's max current capability.

The battery pack has output voltage options through a button which are ranging from 9V up to 20V. I am willing to use the 20V option in order to satisfy my requirement.

Also, i am thinking that in this way i could use some analog switch in conjunction with a microcontroller to create 3-4 output voltage options (messing with the buck converter fB circuit) in order to waste less power when transmitting power required is less than the max achievable level or even better if the buck converter has some dedicated pins either analog or digital for this purpose.

So, a few things that come in mind are

  • output ripple & noise levels
  • use of additional LC filter or passive differential output filter
  • transient response during current peaks drawn by the PAs
  • stability disturbance due to the fast transient current peaks 
  • output MLCCs ESR
  • efficiency during light load conditions

I was looking at the LM76005 and saw that the efficiency was quite good and output ripple is not bad as well however i need a bit more information whether that buck converter is suitable for use with RF PAs.

Can you pls help me out here?

Regards to all

Manos Tsachalidis

  • Hello

    You have listed several good points in your list; all of these should be carefully tested.

    I think the the LM76005 would be a good choice, as would the LM73605 and LM73606.

    We also have a newer device, the LM61460.

    All of these devices use low ESR ceramic capacitors and the LM61460 has low EMI.

    The best way to test the suitability of the device is to get an EVM for the regulator

    you are interested in and test with your application on the bench.

    Thanks