LTM2883

Hi Keith, 

The LTM2883 is protocol agnostic, meaning it doesn't necessarily need to be used for I2C. But it is only the SDA channel that is bidirectional. The SCL channel only transmits forward. It could be repurposed to support other open collector data though.

But the LTM2883 can't support a 7V logic directly. That would violate Absolute Maximum Rating. Can you describe the 0V to -7V logic or device that is being isolated?

Regards,

Jason  

thank you jason,

The other device is very old and uses 0v as a 1 and -7V as a 0.  It is not happy with less then -6.75V.

In transmit mode the standard 3.3V logic transmits data and clock at a very slow rate KHz.  The 3.3V side receives an acknolwedge signal in return.

In receive mode the standard 3.3V logic receives data and clock.  The 3.3V sends the acknowledgement.

The LTM2883 handles up to +12.5V and -12.5V.  I have an evaluation board and set it up to convert 3.3V to 0V and 0V to -12.5V.  The -12.5 can be changed to -7V with a single resistor.   I have a transmit circuit working to send 0V when the standard logic is 3.3V and -12.5V when the standard logic is 0V.  I was hoping that I could make it work in both directions for all 3 lines.

Hi Keith,

If you need additional bidirectional channels, you can consider the ADuM1250 or ADuM2250.

Let me clarify the abs max though. The integrated isolated dc/dc converter of the LTM2883 can indeed provide a +/-12.5V supply. But the digital I/O cannot interface with 7V logic directly. That will violate the abs max for the I/O pins.

Regards,

Jason

Hi Keith,

If you need additional bidirectional channels, you can consider the ADuM1250 or ADuM2250.

Let me clarify the abs max though. The integrated isolated dc/dc converter of the LTM2883 can indeed provide a +/-12.5V supply. But the digital I/O cannot interface with 7V logic directly. That will violate the abs max for the I/O pins.

Regards,

Jason