AMC3301: Ground reference and buffer

Erik Friesen

Part Number: AMC3301
Other Parts Discussed in Thread: OPA2317, , AMC1301, AMC3330

Could there be any issue with a midpoint divider then unity gain buffer like I have drawn here? This schematic was originally drawn for the AMC1301, and I'd like to convert this to use the AMC3301 instead, using something like the OPA2317 as a unity gain buffer.

The probe in this design consists of a 2k shunt in a galvanic o2 sensor, so this precludes direct connection. The output range is 0-200mv dc.

With only 1ma usable external power, this doesn't leave a lot of good options for midpoint buffering. The datasheet shows connecting HGND to the negative side of the shunt, I assume this is only to keep the common mode input range correct.

The AMC3330 has no stock or I'd have used that part.

Any comments or suggestions?

over 3 years ago

0 Alexander Smith over 3 years ago

TI__Guru 50191 points

Hi Erik,

Unfortunately the sourcing issues you are experiencing are widespread across our industry.

You are correct that connecting the HGND to the negative side of the shunt is primarily for keeping the input voltage within the common-mode input range, but this connection also serves to cancel the common-mode input noise.

The only potential issue I see with connecting to the mid-point like this is the power source, ISO_VDD and ISO_VSS. How are these voltages being generated and will they be capable of floating in line with the sensor?

0 Erik Friesen over 3 years ago in reply to Alexander Smith

Prodigy 230 points

In this case, the AMC3301 DCDC would supply this voltage, like this.

0 Alexander Smith over 3 years ago in reply to Erik Friesen

TI__Guru 50191 points

Hi Erik,

This should work!

If you plan on conducting EMI testing I'd encourage you to take a look at this document before moving on to the layout phase: https://www.ti.com/lit/an/sbaa515/sbaa515.pdf

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AMC3301: Ground reference and buffer