Electronics > Projects, Designs, and Technical Stuff
ICL7135 ground loop
davorin:
Well I just ordered some ICL7135 today @ Digikey for testing...but the TC500 series looks promising...just reading their appnote...
but then again...the linecard design features isolated CAN for communicating to the main controller (with GPIB/USB/Ethernet) and isolated power supply...
so no matter what the frontend chip is...it is (or should be ;o) easily replaceable...
Dr. Frank:
I used the 7135 over 25 years ago, with a small 6502 and VIA chip, sharing 5V supply, for different thermometer sensors, PT100, special T-diode, a AuFe/Ni thermocouple.. required a 7650 chopper amplifier for x100 gain for 1µV resolution.. as long as the sensor is isolated from the digital ground there's no problem with ground loops, worked very well.
I used the counting method, with a gate, very easy, as described in the datasheet, with IRQ and FP arithmetic, everything written in assembler.
I still have this PCB /module somewhere.
Frank
bin_liu:
It is recommended to use digital isolation. The power supply can use a module like B0505S-1WR2, but I think the 7135 circuit is more complicated. There are several peripheral components that need special attention. I have about 10PCS for the 7135. It is not easy to consider using it in the future. It’s a collectible. ;D
davorin:
Thought of using this one:
https://www.digikey.com/product-detail/en/murata-power-solutions-inc/NXJ1S0505MC-R7/811-3094-1-ND/5697921
SMT and 4.2kV isolation...and should arrive tomorrow for testing...
Yeah I know that the ICL family is kinda obsolete...but it fits to my other chips I am still keeping since 30 years (o;
The TC510 will be on my next digikey order (o;
Kleinstein:
In principle that power module looks good, but the ICL7135 also need some negative supply. So the more logical way would be a 12 V DCDC and than some local LDO / virtual ground to make the +-5 V.
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