• State TI Thinks Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 2 answers
  • Subscribers 36 subscribers
  • Views 816 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PCA9517: PCA9517 output low level problem

Ken Chen39
Intellectual 545 points
Part Number: PCA9517
Other Parts Discussed in Thread: TCA9509, TCA9803

The value of PCA9517 Vol is different from that of Vol in SMBUS2.0 protocol. Could you please answer it?

  • 0
    TI__Guru 62920 points

    Hi Ken,

    The "B" side of the PCA9517 uses a static voltage offset in order to properly sense the intended direction of data flow.  For this reason, it is a little higher in voltage.  You can read more about how static-voltage-offset buffers work in this application note:

    http://www.ti.com/lit/an/scpa054/scpa054.pdf

    Please let us know if you have further questions.

    Regards,
    Max

  • 0 in reply to Miguel Robertson
    Prodigy 30 points

    PCA9517 can not be applied SMBUS application

  • 0
    TI__Guru 53575 points

    Hi Ken,

    This device is intended for use in I2C and SMBUS applications. While PCA9517 does not meet all specifications set by SMBUS, it is designed to be compatible with devices that adhere to this standard. The standard defines that other devices should have an low-level input voltage of 0.8V and will therefore recognize the output low of PCA9517. As Max mentioned, PCA9517 has a slightly higher low-level output voltage because of the static-voltage-offset used by the buffer. The device is able to implement this buffer method while still remaining within compatible operating specifications for SMBUS.

    Let me know if you have any more questions.

    Regards,
    Eric

  • 0 in reply to Eric Schott1
    Prodigy 30 points

    I need to pin to pin to replace PCA9517DGKR. Is there any product recommendation that complies with the SMBUS specification?

  • 0 in reply to user6311762
    TI__Guru* 77241 points

    The 9517 while is not 'compliant' to I2C/SMbus standard it is is compatible, meaning that any I2C/Smbus compliant master/slave device connected to it will be able to function properly. The ViLc on B side of the device was selected to be 0.4V because I2C standard dictates this to be the highest VoL at a given 3mA IoL.

    If you are hard pressed on finding a I2C/Smbus compliant repeater, then the closest thing you will find is a dynamic offset buffer (as opposed to 9517's static offset buffer). But none of our dynamic offset buffers are pin to pin with the 9517. Dynamic offset buffers may also violate the VoL spec you are referring to under certain conditions. (their Vol are dependent on the input VoL which if high enough wold go laregr than 0.4V after the dyanmic offset is added to it).

    If you are looking purely for a device with a VoL lower than 0.4V on its static offset side then the only devices I can think of are TCA9509 (B side must be larger than A side by 1V) and TCA980x (does not support 5V logic).

    -Bobby

  • 0 in reply to BOBBY
    Prodigy 30 points

    Test TCA9803 found that Vol max = 434mV is inconsistent with the data sheet range(Vol max = 0.26), why？

  • 0 in reply to user6311762
    TI__Guru* 77241 points

    Hello,

    Sorry I didn't see your message until now.

    Is this the A side of B side of the device? If A side, then what is the pull up resistor value you are using?

    -Bobby