ISO1540: 2 side to 1 side

Shuji Ishiwata

Part Number: ISO1540

Hi Team,

I have a question about ISO1540.

1, Can we use it from 2 side to 1 side?
5V → 2 side: ISO 1540: 1 side → 3V
2. Please tell me how to termination of unused pin.
3, How much current can ISO1540 put on the bus line?

Best Regards,
Ishiwata

over 5 years ago

0 Koteshwar Rao over 5 years ago

TI__Mastermind 49445 points

Hi Ishiwata-san,

Please find below my inputs. Thanks.

1. ISO1540 has two sides (Side1 & Side2) with different output current capability and load capacitance support. Hence, Side1 should always be connected to the I2C node (host or slave MCU) that needs isolation and Side2 should be connected to rest of the I2C where multiple nodes can be connected. In other words, Side1 should be connected to only one device while Side2 can be connected to multiple I2C devices.

2. The unused I2C pins can be left floating as they are open collector/drain.

3. ISO1540 outputs are open collector/drain hence, they do not source any current by themselves. ISO1540 Side1 is rated to sink upto 3.5mA while Side2 is rated for 35mA. Since the external pull-up resistor decides source and sink current, the value of external resistor should be chosen accordingly. Please remember to also consider the pull-up resistors from other nodes on the I2C bus while calculating the resistor value.

Regards,
Koteshwar Rao

0 Shuji Ishiwata over 5 years ago in reply to Koteshwar Rao

Genius 5905 points

Hi Koteshwar Rao-san,

Thank you for your response.

Can ISO1540 transmit from 2 sides to 1 side with 1 to 1 connection?

Best Regards,
Ishiwata

0 Koteshwar Rao over 5 years ago in reply to Shuji Ishiwata

TI__Mastermind 49445 points

Hi Ishiwata-san,

Since ISO1540 is a bidirectional I2C isolator, yes you can transmit data from either direction - both Side1 to Side2 and Side2 to Side1. Thanks.

Regards,
Koteshwar Rao

Isolation

Isolation forum

ISO1540: 2 side to 1 side