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ISO7740: ISO7740 Pin 10 is different with ADUM1410

Chen Alex1
Genius 3665 points
Part Number: ISO7740

HI Sir

I Try to use the ISO7740 to replace ADI/ADUM1410

original circuit is work correct, but after change it, the system no work

after check the data sheet

i found the ADI/ADUM1410 pin 10 Is a function pin & connect to ground in my design

but ISO7740 is close the IC , when pin 10 is connect to ground, work abnormal

please advise

thanks

  • 0
    TI__Mastermind 26120 points

    Hello,

    Thank you for reaching out. The ADUM1410 and ISO7740 have slightly different functions for pin 10. On the ADUM1410, pin 10 controls the default output of the device (expected device output when input power is off). For example, if pin 10 is low, the default output will be low, and if pin 10 is high, the default output will be high. However, the ISO7740's default value is not programable and is built into the device. You can determine what the default is by the presence or absence of the F suffix in the part number, the ISO7740 device has a built in default of high, and the ISO7740F has a built in default of low. Since your original design was grounding the pin on the ADUM1410 for a default low signal, you would want to use the ISO7740F.

    Since the ISO7740 does not have a programable output, pin 10 of the ISO7740 serves a different purpose. Pin 10 serves as the enable pin, which controls whether the device's outputs are enabled or disabled. If pin 10 is low the outputs will be disabled and all the output pins will be in a high impedance state. If pin 10 is open or high, the outputs will be enabled and match the inputs of the device. Since pin 10 is grounded in your design, it is permanently tied low and and all outputs will be disabled. Please disconnect pin 10 of the ISO7740 from ground and either leave the pin open or tied high for the outputs to be enabled and work as expected.

    Regards,
    Darrah