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P82B96: Level shift by using TCA9517

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Replies: 16

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Part Number: P82B96

Hi,

I would like to ask you a question about "level sifting".

My customer is planning to use I2C I/F with "CPLD" (master) as below.

 CPLD(master) --- P82B96 --- EEPROM(slave)

But the I/F level between master and P82B96 is difference, master "L" is 0.8V(typ) and P82B96 is "0.88(typ) and 1.0V(max)".

So to solve this situation, the customer is considering to use TCA9517-Q1 or TCA9306-Q1 as "level shifter".

That is to say,

CPLD(master) --- TCA9517(or 9306) --- P82B96 --- EEPROM

CPLD --- TCA9517 : 3.3V or 1.8V 

TCA9517 --- P82B96 : 5V

TCA9517 will be used as "level shifter" in this case.

I would like to ask you, is it possible this kind of usage, right?

Thank you very much for your support.

Best Regards,

Takumi

  • Hello Takumi-san,

    Our team is currently out of the office due to the US holiday, but we will get back to you later this week.

    Regards,
    Max

  • In reply to Max Robertson:

    Hi Max-san,

    Thank you for your kindness!

    Let me wait for your reply.

    And I got an additional information from the customer as below.

    ==============================

     *** P82B96 → TCA9517/9617B  (LOW I/F)      :     seems to be OK

      P82B96 VOL 0.67V~0.79V

      TCA9617B VIL ~1.5V

    *** TCA9517-Q1/9617B →  P82B96 (LOW I/F)  :   risky??

      TCA9617B VOL 0.45V~0.6V

      TCA9617B VOL 0.48V~0.58V

       P82B96 VIL 0.6V@+25 °C、0.55V@+50 °C

    ==============================

    Condition ---  VccA:3.3V、VccB:5V、IOL=500uA

    If TCA9517 seems not to be appropriate to use as an interface, please let me know another solution.

    Thank you so much in advance.

    Best Regards,

    Takumi

  • In reply to Takumi Suzuki1:

    Hey Takumi,

    How exactly is the customer using the P82B96? In your original post you had:

    master <-P82B96-> EEPROM

    However the P82B96 is meant to be used in a pair and for cable transmission.

    The Sx/Sy side of P82B96 cannot interface with any static voltage offset sides of an I2C buffer. So B side of TCA9517/9617 cannot connect to Sx/Sy of P82B96.

    Making B side of either of those devices means they must face the master which has a VoL worst case of 0.8V which is larger than the ViL/ViLc on B side of the TCA9517/9617.

    Can you provide a snapshot of the VoL spec from the master (from datasheet)? Typically the VoL is spec'd based on an IoL level.

    Also can you check why the customer chose to use the P82B96? I'd like to know if this is the correct device for their application.

    -Bobby

  • In reply to BOBBY:

    Hi Bobby-san,

    Thank you very much for your reply.

    I checked the configuration of the customer.

    Sorry, I misunderstood the system, the right configuration the customer is considering is as below.

            CPLD(master) --- TCA9517 --- P82B96 --- cable --- P82B96 --- EEPROM(slave)

            master : 3.3V power, VIL=0.8V(max), VOL=0.4V(max)

            I2C line : 12V

     Let me ask you again, is it possible to make this configuration?

    And I got the specification of the CPLD.

    As I would like to send it to you, please let me know your e-mail address?

    Thank you for your support.

    Best Regards,

    Takumi

  • In reply to Takumi Suzuki1:

    Bobby-san,

    Will you tell me your e-mail address?

    Let me send you the specification of the CPLD.

    Thanks!

    Best Regards,

    Takumi

  • In reply to Takumi Suzuki1:

    Hey Takumi,

    You can send me an email at duynguyen@ti.com

    Thanks,

    -Bobby

  • In reply to BOBBY:

    Bobby-san, thank you !!

    Best Regards,

    Takumi

  • In reply to Takumi Suzuki1:

    Hi Bobby-san,

    Thank you very much for your kind support.

    As a result, the customer gave up using TCA9517.

    But the customer is considering to use PAC9306 instead of TCA9517.

    That is to say,

     CPLD(master) --- PCA9306 --- P82B96 --- (cable) --- P82B96 --- EEPROM(slave)

     CPLD - PCA9306 : 3.3V, PCA9306 - P82B96 : 5.0V

    How about this configuration?

    I suppose it seems to be OK but I would like to ask you your idea about this.

    If it is possible to use, will you give me the reference circuit schematics?

    If it is not, please tell me another solution?

    I appreciate your strong support very much!

    Best Regards,

    Takumi

  • In reply to Takumi Suzuki1:

    Takumi Suzuki1

    Hi Bobby-san,

    Thank you very much for your kind support.

    As a result, the customer gave up using TCA9517.

    But the customer is considering to use PAC9306 instead of TCA9517.

    That is to say,

     CPLD(master) --- PCA9306 --- P82B96 --- (cable) --- P82B96 --- EEPROM(slave)

     CPLD - PCA9306 : 3.3V, PCA9306 - P82B96 : 5.0V

    How about this configuration?

    [Bobby] Unfortunately this won't work. PCA9306 is a level shifter only device, it does not redrive the low level signal. So ~800mV VoL from P82B96 will still generate a ~800mV low through the PCA9306. Any low from the CPLD will be shown at the same level plus some shift up to the P82B96 as well.....

    I suppose it seems to be OK but I would like to ask you your idea about this.

    If it is possible to use, will you give me the reference circuit schematics?

    If it is not, please tell me another solution?

    [Bobby] How far away is the cable length? I'm wondering if we could pass the signal using: CPLD---(PCA9306 if needed)---TCA9511A--Cable--TCA9511A---EEPROM

    I appreciate your strong support very much!

    Best Regards,

    -Bobby

  • In reply to BOBBY:

    Bobby-san,

    Thanks for your reply!

    I'm sorry that PCA9306 is not the apropriate device in this application.

    Thank you for your recommendation of TCA9511A.

    About the cable length, it seems to be around 30m - 40m...

    I suppose 30m seems to be difficult to drive for PCA9511A.

    What do you think of the distance?

    If it is difficult to drive, is there another device to recommend??

    Thank you so much for your kind.

    Best Regards,

    Takumi

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