Can digital isolator go high (or low) and stay high (or low)?

[cupoftea]

ISO672X

https://www.ti.com/lit/ds/symlink/iso6721-q1.pdf?HQS=dis-dk-null-digikeymode-dsf-pf-null-wwe&ts=1673852830337

...datasheet doesnt say...its capacitively coupled so you infer from that that it needs a constantly changing input to work?

 

[FvM]

Read the datasheet thorougly, not just the headline.

 

[cupoftea]

Thanks, yes, it has a carrier, of high frequency, but they dont say how high.
They avoid referring to it (on all the time), as i guess, most comms lines dont do ON all the time..they have eg Manchester coding.
Also, it says what the infineon gate drivers say, and i have just had a reply from the official infineon forum saying they dont do 100% duty with any of their isolated gate drivers...this has blown my entire reality check totally out of the water on this subject. My compass on this is now just spinning round and round.

 

[FvM]

Most "non-optical" (inductive, capacitive) isolators are using modulation. Frequency is relative high and shows in delay and jitter rather than dc specs.

i have just had a reply from the official infineon forum saying they dont do 100% duty with any of their isolated gate drivers

What do they exactly say? Drivers aren't tested for 100 % duty cycle? Or they have a maximal on-time spec? 0 % duty cycle (infinite off) should be supported hopefully.

--- Updated Jan 16, 2023 ---

Referring specifically to TI digital isolators, they are clearly suited for DC signals (infinite duty cycle).

 

[stenzer]

Hi,

I have used the this kinds of (OOK) isolators several times. Main appliction for me was to isolate a SPI bus, where individual !CS signals have to stay HIGH or LOW to avoid an interference between the individual slaves. I haven't had any issues.

Also the detailed description in section 9, clearly indicates the usage of DC signals, as a LOW signal is represented by the CF and a HIGH signal by its absence.

BR