Background:
I added a circuit for TI's LM2674 which is a Power Converter High Efficiency 500mA Step-Down Voltage Regulator (http://www.ti.com/product/lm2674) This requires an inductor, which I am using Coilcrafts D03308 (http://www.coilcraft.com/do3308p.cfm). (see: "layout.jpg")
The device I am working on amplifies biosignals (~1 - 10 mV) with an AD623 and the op-amp, TLC2272 to an audio jack. It also amplifies the signal with a LM386 to an 8Ohm speaker. We are using the Voltage Regulator to split the power for the instrumentation amps to be on regulated voltage and the speaker amp would be on the 9V battery. We are trying this because if we turn up the gain on our LM386, we get feedback when these three ICs are on the same power source.
Issue:
With the new board I built up, there is an unwanted hum over the signal. Other than the addition of the Voltage regulator circuit and arranging the board, nothing has been changed.
My guess:
The inductor is creating and EMF that is creating this hum on our signal trace. I read that it was shielded but perhaps it's still too close? (see "issue01.jpg")
My question:
How much space do I need to give the EMF-inducing components so they don't interfere with the sensitive signals? Does anyone have experience with this LM2674 circuit in particular?
I added a circuit for TI's LM2674 which is a Power Converter High Efficiency 500mA Step-Down Voltage Regulator (http://www.ti.com/product/lm2674) This requires an inductor, which I am using Coilcrafts D03308 (http://www.coilcraft.com/do3308p.cfm). (see: "layout.jpg")
The device I am working on amplifies biosignals (~1 - 10 mV) with an AD623 and the op-amp, TLC2272 to an audio jack. It also amplifies the signal with a LM386 to an 8Ohm speaker. We are using the Voltage Regulator to split the power for the instrumentation amps to be on regulated voltage and the speaker amp would be on the 9V battery. We are trying this because if we turn up the gain on our LM386, we get feedback when these three ICs are on the same power source.
Issue:
With the new board I built up, there is an unwanted hum over the signal. Other than the addition of the Voltage regulator circuit and arranging the board, nothing has been changed.
My guess:
The inductor is creating and EMF that is creating this hum on our signal trace. I read that it was shielded but perhaps it's still too close? (see "issue01.jpg")
My question:
How much space do I need to give the EMF-inducing components so they don't interfere with the sensitive signals? Does anyone have experience with this LM2674 circuit in particular?
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