Hi,
how does your input signal looks like? Single continuous wave (CW) frequency? Amplitude?
Which kind of mixer do you want to use? Active or passive? What's the mixer's conversion loss or gain? Mixer application, IF or direct-down conversion?
According to Friis formula of noise, you should place the amplifier/opamp before your mixer. Other way arround your mixer noise is also amplified.
Further, if you are realizing a direct-down conversion (zero-IF) also a possible DC offset caused by a local oscillator leakage will be amplified by an amplification after your mixing stage.
As KlausST already stated, option 2 is cheaper as you have lower requirements for your opamp ciruitry e.g. bandwidth and slew rate.
greets
What´s your sampling rate per channelUse the uC ATSAME54P20A to capture and process the data.
My style is to treat all inputs most equally, thus I´d rather use just 5 ADC channels and 5 pieces of 8-to1-Demux. But that´s a personal taste.1) The uC ATSAME54P20A provides 32 ADC inputs. And I need to sample 38 currents. Therefore the uC has not enough ADC inputs to cover the first requirement.
(I have quite a lot of experience with the HTAxxx Current transducers. Regulation loops down to some 10s of mA AC with a HTA1000. DC stability is worse, especially when you expect some overcurrent peaks --> remanence effects)The output HTA 300-S current sensor is +-4V (denpens of the direction of the current) and the range if uC ADC inputs goes from 0V to 2.5V. So I need to scale the output sensor voltage to fits with the ADC input range because when I process the data in the uC, I need to detect direction and value of the current through RS.
Hi!
Thanks for your quick reply.
I try to answer your questions:
1) The sampling scheme is channels interleaved.
2) The ADC resolution is 12 bits and I am expecting to measure currents with a +-1.5% of accuracy in the hall effect sensor range: 0A / 300A
I like your proposal with five 8:1 demux and I regarding to the power supply of the current sensor....I did not think about that, but your proposal of using unsymmetry power supplies and drive Vref/2 to the 0V of sensor sounds also good for me. Is there any reference design of your proposal?
Thanks!
I´m missing some details.Is this the solution you were talking about?
Traco rating = output rating = P_VC+ = 15V * 38 * 0.025A = 14.25WP_VC+ = 16.25*0.95A*0.85=13.12W
P_VC+ = 13.75*0.95A*0.85=11.1W
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