It seems to be that this is not possible to find in one chip. I found ADAS3022 which has 8 inputs high impedance, 0-5V and 0-10V input 16bit. But this consumes quite much current.
I also found AD7171 which is low power but needs external reference 5V for 0-5V, external MUX and may be external buffer for high impedance. I know that there were multimeter circuits like ICL7109 which had very high input impedance, stable values, but unfortunately no 0-5V input and no multiplexer in front.
I would need a solution for a data logger - battery driven - and therefore need something with very small current consumption that does not need to be very fast. 100 Sps or so would be ok. May be somebody has an idea.Thank you very much !
Thank you Daryl,the supply voltage is not so sure at the moment. May be there will be 3.3V and 5V. Thank you for the hint to the AD7689. I will have a look at the data sheet.8 external OP amps are possible - but this takes quite some space for all those and may be as well the series resistors and caps according to the data sheet http://www.analog.com/media/en/technical-documentation/data-sheets/ADA4805-1_4805-2.pdf. The offset may differ from channel to channel then. 125uV means some LSBs. Using 5V as supply may be some upper bits are lost or the op amps would have to be supplied by 5.5V or so. When using the ADR4550 with 300mV drop also the 5.5V could do.Another possibility would be using an external MUX like DG406 and a buffer amp after this in front of the ADC. Using this only one amp would be necessary. Also using a divider up to 10V also would be possible.Regards,Matthias