ISO6763: Design with ISO6763DWR

Intellectual 585 points

Part Number: ISO6763
Other Parts Discussed in Thread: SN74LVC1G08, SN74LVC1G125, ISO6741

Tool/software:

Hello Team,
We are using the IC ISO6763DWR for one of our application.

We have a 3.3V SPI from an MCU to be isolated with a 5V ADC.
The SPI speed is 5MHz

the default output of the ISO6763DWR is high.

Does this mean when the input is at high impedance, the voltage at the out is HIGH.

We have another SPI slave connected to the same but in the non isolated side.
since CS of the ADC is high (ship is not selected), the MISO pin will be floating or can be high or low and the corresponding out can be either high or low.
Will this create any problem to the other SPI slave device connected to the non isolated side of the SPI.

Can anyone please suggest a digital isolator with output enable?.
Looking for your reply

8 months ago

0 Clemens Ladisch 8 months ago

Guru 318050 points

The isolator will always actively drive its outputs. To be able to combine multiple MISO signals, disable the isolator's output signal by adding any '125 gate (e.g., SN74LVC1G125) controlled by the /CS signal. Alternatively, combine multiple MISO signals that are high when idle with an AND gate (e.g., SN74LVC1G08).

0 Sv 8 months ago in reply to Clemens Ladisch

Intellectual 585 points

Hello Team,
Is there any digital isolator with an output enable pin?.

0 Aaditya V. 8 months ago in reply to Sv

TI__Mastermind 18525 points

Hello,

Thanks for reaching out.

From the schematic and clock diagram you have attached, it seem that you need 3 forward channels and 1 reverse channel digital isolator. The ISO6741 is a 4-channel isolator (3 forward, 1 reverse) and has output enable pins. Please check this device here: https://www.ti.com/product/ISO6741

Sv said:
Does this mean when the input is at high impedance, the voltage at the out is HIGH.

Yes, your understanding is correct. Please check this FAQ for information on F vs non-F devices: https://e2e.ti.com/support/isolation/f/1013/t/1130157

Regards,
Aaditya V

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ISO6763: Design with ISO6763DWR