ISO1540: Designing with ISO1540DR

Part Number: ISO1540
Other Parts Discussed in Thread: ISO1640

Hello Team,
We are using ISO1540DR for one of our applications.
The following is the block diagram of the same.

The IC INA238AIDGST is used to measure some voltage.
The voltage measured is isolated from the MCU supply voltage.
So we are using a digital isolator in between.

Do we need 2 digital isolator?.
The I2C address of the I2C slaves will be different.

Looking for your reply

5 months ago

0 Andrew Jackiw 5 months ago

TI__Mastermind 20605 points

Hello Sv,

Thank you for looking into our isolators. Side 2 of ISO1540 is capable of handling multiple I2C nodes. The I2C isolator will simply pass the signals from the MCU (master) to the two INA controllers.

Also, please see ISO1640, which is the newest I2C device in the portfolio.

Best,
Andrew

0 Sv 5 months ago in reply to Andrew Jackiw

Intellectual 360 points

Hello Andrew,
Thank you for your reply.
Below is the schematic for the same.

The side VCC1 have 2 I2C slaves.
Also, is there any voltage sequencing required.
In some digital isolators I've seen, the VCC1 should be greater than VCC2.
or VCC1<VCC2

+1 Andrew Jackiw 5 months ago in reply to Sv

TI__Mastermind 20605 points

Hello Sv,

Thank you for the additional details. ISO1540 does not need VCC1<VCC2 the two sides are considered completely independent.

Sv said:
The side VCC1 have 2 I2C slaves.

It is not recommended or side 1 to drive more than one I2C node. Please see (+) [FAQ] ISO1640: Why are the maximum load capacitance and load current ratings for Side 1 of the ISO1640/ISO1641 less than Side 2?

Best,
Andrew

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ISO1540: Designing with ISO1540DR