ISO7720: ISO7720 application issue

Intellectual 980 points

Replies: 3

Views: 85

Part Number: ISO7720

Hi teams

My customer has a new requirement I listed below:

3.3V(High)-0V(Low)input to 3.3V(High)-1V(Low) Output. 10Mbps data rate.

I have an idea to achieve this requirement with our ISO7720 and need to double confirm with you.

Below is my question:

  1. Could we supply the device with 3.3V to VCC2 and 1V to GND2 to achieve this? (3.3V and 0V is applied to VCC1)
  2. If it could will it output a low level with 1V in output?
  3. Could we generate the 1V from VCC1 to power GND2? (Customer didn't need isolation actually)

3 Replies

  • Hi Gabriel, 

    I think there may be an issue here. If you supply 3.3V to Vcc2 and 1V to GND2, you are essentially giving 2.3V power supply to the ISO7720. This is very close the the UVLO threshold which may mean if the power supply is not well regulated the device may get stuck in UVLO during normal operation. 

    For my understanding, can you explain why the LOW signal has to be shifted up to 1V instead of 0V?

    Best regards, 

    Dan

  • In reply to Dan Kisling:

    Hi Dan

    Customer end equipment is LED wall driver.

    They leverage a 4V bus for LED driver IC to control the LED current.

    But as R/G/B/W LED forward voltage is different so some specific color LED won need such large headroom voltage.

    They create a 1V GND voltage for some LED to reduce the headroom voltage.

    So for these LED driver the control signal GND is 1V.

    I have tried this connection in ISO7721 EVM but it didn't work.


    I increase the input voltage to 4.5V and leverage TLV62569 (non-isolated buck converter) to generate 1.5V output.

    Under this condition the supply voltage for ISO7721 is 3V. But after I connected 1.5V to GND2 the buck output will be pump to also 4V.

  • In reply to Gabriel Xu:

    Hi Gabriel, 

    Sorry for the delay in response - the US had a holiday weekend. 

    Would you be able to draw a quick schematic of what you have tried so far so I can analyze it further? 

    Best regards, 

    Dan