Hello forum,
What is best parts/values to use around VS/REF pins to mitigate high frequency over/under shooting pulses on 240 output. REF1,2=AGND. Can 240 produce True RMS results compared to other industry current measuring devices, it seems in no way possible. Perhaps some manufactures falsely claim results are True RMS (Peak mV/A * 0.707)? Yet in our case 240 low end (0A<8A) RMS monitor values are well above typical, if we are to believe the web shunt error calculator results, 500uohm or 2mohm shunts were tested. Both shunts produce about the same error results from RMS values the 12 bit SAR converted.
Typical VS pins bypass (4.7uf/0.1uf) on 3v3 supply input. Example; datasheet (FAN4174) amp suggest 6.8uf / 0.01uf placed close VS pin to maintain 4mHz GBWP.
The 240 datasheet does not elaborate differential amplifier design or best parts values/methods to mimic CMRR (Fig.12) or GainVsFrequency (Fig.10) around 400kHz BW. Seemingly graphs (GainVsFreq) and CMRR roll off occurs near 400kHz under what VS/REF pin frequency conditions?
1. Order to produce similar results (CMRR Fig.12) does 400kHz BW have to be constrained relative to the VS,REF pins parts values?
2. Why does output over/under shoot occur if Fig.10 (GainVsFreq) shunt peak pulse amplitude & frequency & CMRR Fig.12 graph values fall well below 20V/V gain?
3. Seemingly GainVsFreq roll off curve near 1Mhz Fig.10 is being inverted, how is that possible? Test results indicate frequency gain increases opposed to Fig.10/12 indicate BW roll off occurs.
4. Can high frequency ripple (1.5Mhz) on VS pin mitigate or even invert CMRR and or cause GainVsFreq inverted response graphs?