Just want to ask the AD9171 design issue as below:
1. Datashee page 56 showed below info, if can help to explain the following formula in detail:
The ac differential current measured at DACx+ and DACx− is as follows:
IAC_DIFF (mA) = DACCODE/DACCODEMAX × IOUTFS × RINT(RLOAD + RINT)
where: DACCODE = 0 to 65,535 (decimal).
RLOAD is the load impedance seen on DACx+ and DACx−.
2. How to calculate the AD9171 output power?
Thanks a lot.
1. I believe the formula is not exact.
Let me give one example.
DACCODE is 2's complementary code:
When DAC code = 32767, the differential current = 32767/32768 x IOUTFS x RINT (RLOAD + RINT)
When DAC code = 0 the differential current = 0/32768 x IOUTFS x RINT (RLOAD + RINT)
When DAC code = -32768, the differential current = -32768/32768 x IOUTFS x RINT (RLOAD + RINT)
2. Output power = I^2 x RLOAD. For example, for a full scale sine digital code, the RMS power on load of 100Ohm with 20mA full scale settings will be = ~1dBm.