Isolation design help needed.

Thread Starter

random_1uim

Joined Apr 8, 2021
2
First of all thanks for reading this post. I am designing an isolated board for several peripherals for which I need your help/suggestions. The board contains a buck converter (like LM2596) to step the input voltage from (9-36V) to 5 V. Then there is an isolation converter ( Vin=5V, Vo=5V isolated). My first questions is regarding this isolation converter. The only component I could find online is 0505 series (0505 converter) which is limited to 1 W only. I need at least 1.2 Amps of current supply. The peripherals include one isolated RS485 transceiver, one CAN bus transceiver and two or three ADC connected via I2C bus with a digital isolator between ADC and microcontroller. Following are my questions regarding this board and I would really appreciate your help.

Is there any similar model like 0505 converter(isolated) with higher power handling capacity?

Is the board design ok? with respect to isolation!

The microcontroller runs on 3.3 V so I would need to use a 5 to 3.3 V linear regulator, would that effect the performance too much? is so should i go for 5 to 3.3 V isolated converter?

Any other suggestions regarding this design?

Here is the picture of this board.


photo_2021-04-08_09-01-38.jpg
 

crutschow

Joined Mar 14, 2008
27,718
Have you tried to find an isolated step-down converter so you only need one conversion?
A flyback converter may work since the are inherently isolated.
Here's some info on them.

Why do you show the input and output of the devices apparently connected to the non-isolated and isolated power?
I would need to use a 5 to 3.3 V linear regulator, would that effect the performance too much?
It depends upon the current.
A linear regulator dissipates power equal to the difference in the input and output voltage times the current.
 

Thread Starter

random_1uim

Joined Apr 8, 2021
2
Why do you show the input and output of the devices apparently connected to the non-isolated and isolated power?
Thanks for your reply, these are isolated transceivers, the block diagram may look a little confusing, In fact, the connections show the isolated and non isolated power lines, the data connection is shown with a dashed line.
I am inclined to use flyback converter now as it is inherently isolated. the current drawn by thee microcontroller is 300mA so a linear regulator should be fine i think.
 

du00000001

Joined Nov 10, 2020
78
One DC/DC 10 W converter with output regulation would be the RECOM REC-10 series. These do not come with a 5 V input, but why not use one with a 9-36 V input - a perfect fit if your input specification (from the drawing) holds. And if you need only 3.3 V on the MCU side, these are available with a 3.3 V output as well.

Having seen the schematic drawing, I still cannot understand why you want your MCU to run isolated at all. Or do you intend to implement an isolated power inverter of some kind where the isolation of the MCU would be one of several possible solutions ?
 
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