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P82B96 Supply Voltage Noise & Current limiting resistor

RAVI TEJA
Intellectual 270 points
Other Parts Discussed in Thread: P82B96

Hi,

We are designing a P82B96 based I2C prototype for low frequency (40kHz) long distance (upto 300m) master-slave communication - smart energy meter application. The pull-up voltage on the Long Distance Transmit sides (Tx,Ty,Rx,Ry) is 12V - powered using a 12V 5A SMPS. We are much concerned about the voltage ripples/Noise on the SMPS output. The SMPS datasheet indicate 100mV noise at 45kHz switching frequency.

Can someone please let us know if the above SMPS can safely be used with P82B96 for I2C communication at 40kHz Bus Clock Speed without any interference? Also, please suggest if there is a better way to suppress the noise from SMPS.

Also, do we need to connect a current limiting resistor on P82B96 Vcc pin when connecting it to 12V line?

Regards,

Ravi

  • 0
    TI__Expert 5140 points
    Hi Ravi,

    In regards to the noise, I don't think there's a concern for noise as this is less than 1% of of your total voltage. The only way to suppress this noise would be to add capacitance.

    Also, you will not need a current limiting resistor on Vcc pin.

    Thanks,
    Siby
  • 0 in reply to Siby James
    Intellectual 270 points
    Thank you . And sorry for the delayed reply. I waited to test and reply. We tested the connection today and power supply wise, it just working fine without a current limiting resistor. However, we are unable to establish a successful P82B96 I2C communication link. I shared the details in a new post. We would really appreciate your help if you can take a look and share your suggestions. The link is below,

    e2e.ti.com/.../531147

    Thank you again,

    Ravi