What are the registers and what is the procedure to adjust dBFS levels in DAC AD9164?
I have referred the data sheet of DAC AD9164 but not able to find the registers.
To adjust FS level you need to either change the load or FS current. Changing load is not suggested because it will affect the signal integrity as well. However, changing FS current is easy and feasible.
Changing the FS current is possible by changing the resistor connected between ISET pin and VNEG. Please follow the "Voltage reference" section to find more details.
The FS current value can be adjusted digitally over an 8 mA to 40 mA range by the ANA_FULL_SCALE_CURRENT[9:0] bits (Register 0x042, Bits[7:0] and Register 0x041, Bits[1:0]), as well. The instructions can be found under the "Voltage reference" section, either.
Thank you the helpful response.
How dBFs value and Fs current are related? Is there any look up table for dBFs value corresponding to Fs current? Kindly let us know.
You are very welcome! I'm afraid I don't have an easy answer for you! dBFS is the power level and FS current is just current level. The power level depends on the load and portion of the FS current that is delivered to the load.
For example, in the case of the current AD916x eval boards, as mentioned in the datasheet, the source load (including 2xRINT, RL, and 2xRpullup) seen from the DAC ac current source is equal to:
The total source load seen from the ac current source is 29Ω:
We are using a 1:1 load ratio balun. Thus, V2 is equal to V1:
where is the peak differential current delivered to the load, is the peak voltage measured across the total load and is the total RMS power delivered to the load. In dB, the output RMS power is -24.7dB. Since this power is gained at FS current, the output RMS power is -24.7dBFS.