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ISOM8113: Storage Delay

Pjs
Intellectual 900 points

Part Number: ISOM8113

Hi, 


Please can you provide some further information on the storage delay parameter. Can you let me know:

  • Is the storage delay temperature dependent - is there a way to track expected variation?
  • Is the storage delay affected by product lifetime if the environmental and loading conditions are kept consistent (i.e. data is still being transmitted but it's the same capacitive/resistive loading).
  • What element causes storage delay in opto-couplers/emulators?
  • Are you able to provide what the typical storage time might be? I can see there's an Ioff typical and Ts max but not Ts typical. Can this be calculated if we share loading conditions?
  • What other factors affect the storage delay? I.e. does forward current / CTR play a part?

Many thanks

  • 0
    TI__Mastermind 33945 points

    Hello PJS, 

    Thank you for reaching out. 

    1. Storage time (Ts) is a component of TOFF which is tracked over temperature in the typical application figures like Figure 6-25. Switching Time vs Load Resistance
    2. The ISOM811x's timing characteristics should not change with respect to lifetime since the isolation transmission circuits do not degrade. Optocouplers have a LED-aging effect which causes this however, ISOM811x does not have an LED and will not age.
    3. Storage delay in
      1. Opto-emulators is caused by some charge remaining on the output circuits. 
      2. Optocouplers is caused by the characteristics of the LED 
    4. Yes, please see the figure 6-25 (and other curves) in the datasheet. 
    5. Ts and Tr are used to calculate Ts

    Best,
    Andrew  

  • 0
    Intellectual 900 points

    Hi Andrew, 

    Thanks for the quick response.

    >> Storage time (Ts) is a component of TOFF which is tracked over temperature in the typical application figures like Figure 6-25. Switching Time vs Load Resistance

    Thanks, the figures are helpful. How do I find out the typical characteristics for a 1k load, VCC=6V and IF=8.6mA.

    >> Ts and Tr are used to calculate Ts

    Do you mean Tf here? Or some other parameter? Do the forward current or CTR affect the Ts?

    Finally, are there any other opto-emulator parts we should be considering with substantially reduced Ts time?

  • 0 in reply to Pjs
    TI__Mastermind 33945 points

    Hello PJS,

    Specific test conditions may not be covered. You can estimate your test conditions using the Figure 6-7. Collector Current vs Collector-Emitter Voltage and Figure 6-13. Collector Current vs Forward Current graphs. A Vce = 6V with a 1kohm load would result in an Ic_max=6mA. This would be a saturation mode behavior where Ic_max is the limit of IF*CTR. 

    TOFF = Tr+Ts as shown in the graph below since the output will be inverted from the IF signal when using a pull-up resistor. 

    CTR will affect switching performance somewhat. For best switching results, higher CTR variants are preferred. 

    Best,
    Andrew