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[SOLVED] Ground shifting from one level to another

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mrinalmani

mrinalmani

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Is there a way of making a node act as ground, without electrically connecting it to the ground.
I have a PWM signal generated by a MCU. The signal is being generated with reference to the MCU ground. Now I have to drive a MOSFET using this signal, but it is not possible to join the MCU ground and the source-pin of the MOSFET together.
Is there a way of "shifting" the ground level to the source-pin level, without connecting the two pins?
Thanks
 

hi,

Unless the grounds are connected the circuit won't work since the current has to flow back to the source. If your purpose of isolating ground is to avoid noise you may use ferrite beads(having attenutation at that frequency) to connect both grounds.
 

opto-coupler seems inappropriate due to long switching delays.
Desired switching frequency is about 100kHz
 

There are some high-speed optocouplers. SFH6325 has 2MHz bandwidth.
 
Ok, I finally wanna ask... is the use of opto-couplers an industry standard practice? Someone with experience, please provide feedback...
 

Two common ways to isolate grounds is with a transformer or an optical coupler. A transformer can only carry AC signals, of course, but an optical coupler can transmit AC or DC. Which to use is determined by the application requirements.
 
Digital Isolators are a more modern alternative to optocouplers, offering improved performance with lower power dissipation. They’re also much easier to implement in a design since the inputs and outputs use standard digital logic. Standard digital isolators have different numbers of input and output channel combinations and can operate up to 150Mbps. The ADuM124x/144x family might be suitable for the desired throughput rate (100 kHz) and dissipate extremely low power.

You can see the entire digital isolator product line available from Analog Devices at our web site: https://www.analog.com/en/interface/digital-isolators/products/index.html
 
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