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ISOM8111: ISOM8111

GERMÁN LÓPEZ
Prodigy 25 points

Part Number: ISOM8111
Other Parts Discussed in Thread: ISOM8110, ISOM-EVM

Tool/software:

Is posible replace ILD213T by ISOM8111 to work as switching to isolate/protect the input pin of any MCU ?¿

(apart from ILD213T being double)

Thanks in advance !!

  • 0
    TI__Mastermind 34580 points

    Hello German, 

    ISOM8110 is functionally equivalent ILD213T and should be able to drop into the schematic without major changes. Please note that the ISOM8110 is currently only a single channel device, therefore the footprint may need to be changed. 

    Best,
    Andrew

  • 0
    Prodigy 25 points

    Thanks to confirm that both are equivalents.

    Talking about de Low Pass filter with Resistor+Capacitor, wich values do you recomend in input pins of ISOM8111? Any Application Note about it?

    Thanks in adcance !!

  • 0 in reply to Andrew J
    Prodigy 25 points

    Thanks so much Andrew, any Application note with typical connections (or recommended values) to work as switching & input filter (RC, ...)? (no need inputs with high speed)

    Thanks in adcance

  • 0 in reply to GERMÁN LÓPEZ
    TI__Mastermind 34580 points

    Hello German, 

    The filter's cut off value needed for your design will depend on your application requirements. The current filter's cutoff frequency is ~160Hz = 1/(2*pi*10k*100n). This filter selection is okay. The same filter will work for ISOM8110 since it is a functional match for the current design. Please note that faster data rates may be possible since ISOM8110 has a faster isolation technology (BW = 680kHz).

    Best,
    Andrew

  • 0 in reply to Andrew J
    Prodigy 25 points

    Sorry, but is a little confuse for me understand the swithing mode of ISOM8110/1. I find it difficult to understand the relationship between a sufficiently high IF, so that the output transistor works saturated (small VCE), for specific conditions of a 'pull-up' resistor connected to 3V3 (input of my MCU). Could you help me ¿?

    Is this hypothesis presented in the image correct?

    Thank you for your patience.

  • +1 in reply to GERMÁN LÓPEZ
    TI__Mastermind 34580 points

    Hi German,

    The ISOM811x will be in saturation mode whenever the collector current is limited below the IF*CTR, or IF*CTR > IC. This is shown in the figure where VCE = 0.4V. 

    The equations you showed are mostly correct. 

    • RF = (VCC - VF) / IF = (24V-1.4V)/10mA = 2260ohms
    • Rc is correct. However, please note that 4mA limit is set by the pull up resistor. (VCC=5V, RL=4.7kΩ; which corresponds to the Ic=1mA test condition for VCE)

    Best,
    Andrew

  • 0 in reply to Andrew J
    Prodigy 25 points

    Thanks so much, it's already more clear now.

    Finally, we bougth the evaluation board ISOM-EVM to check the diferents values of resistors (RL & RC) vs operations modes (switching, ....).

    BR