• TI Thinks Resolved


Part Number: ISO7742

Hi Sir 

If use ISO7742 for UART interface 

Have any condition need to add external series resistor? just like reduce noise coupling  

  • Hello Kai,

    Thank you for using E2E Forum and for showing interest in ISO7742.
    For normal device operation the resistors at device input pins (like INA) are not necessary but if the system is expected to have noise or transients at input pins of device then yes it is recommended to have RC filters. When the values of RC chosen appropriately the filter serves two purposes,

    1. It filters out any noise at inputs and avoids data corruption. Please choose the value of RC such that the cut-off frequency of the RC Low Pass Filter is slightly higher than the input signal datarate and the rise/fall times are not affected much.

    2. If transients with voltage higher than what the device can support are expected at input pins of device, the resistor from RC filter limits the current (10mA) into and the voltage (5.5V) that appears at device pin thereby avoiding any damage to device. Please choose the value of R such that the max current into the device is limited to what the device can handle for given transient voltage.

    I hope that answers your question, thank you.

    Koteshwar Rao