P82B96: Level shift by using TCA9517

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

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,

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

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,

Bobby-san,

Will you tell me your e-mail address?

Let me send you the specification of the CPLD.

Thanks!

Best Regards,

Hey Takumi,

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

Thanks,

-Bobby

Bobby-san, thank you !!

Best Regards,

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 Suzuki1 said:

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

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,

Bobby-san,

I got an additional question and information from the customer as below.

 - I informed TCA9511A to the customer.

   The customer would not like to use TCA9511A as "cable driver", to use interface between P82B96 and CPLD.

        CPLD－TCA9511A－P82B96 ----- cable -----P82B96－EEPROM

        The cable length is 30m～40m, clock speed is around 50KHz.

        CPLD - TCA9511A : 3.3V, TCA9511A - P82B96 : 5V (Does TCA9511A have level shift function, correct?)

   How about this cofiguration? 

Thanks!

Best Regards,

Bobby-san,

Will you tell me your idea about the cable length?

It seems to be difficult for PCA9511A??

And I would like to ask you an additional question.

Do you know the same/close function device with LTC4313?

www.analog.com/.../4313123f.pdf

Though I checked, I did not find the TI device.

Thans for your support.

Best Regards,

Takumi Suzuki1 said:

Bobby-san,

"

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?

[Bobby] You are correct. I don't expect TCA9511A would be able to drive that amount of cabling effectively.

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

[Bobby] Unfortunately this means P82B96 is the only option if we want to truly buffer the cable capacitance.

Thank you so much for your kind.

"

-----------------------------------------------------------------

I got an additional question and information from the customer as below.

 - I informed TCA9511A to the customer.

   The customer would not like to use TCA9511A as "cable driver", to use interface between P82B96 and CPLD.

        CPLD－TCA9511A－P82B96 ----- cable -----P82B96－EEPROM

        The cable length is 30m～40m, clock speed is around 50KHz.

        CPLD - TCA9511A : 3.3V, TCA9511A - P82B96 : 5V (Does TCA9511A have level shift function, correct?)

   How about this cofiguration? 

[Bobby] The problem with this is the TCA9511A does not work with static voltage offset devices like the P82B96.

The best solution I can think of is:  

CPLD - B sideTCA980x A side : 3.3V, TCA9511A - P82B96 : 5V (TCA980x can level shift but B side cannot connect to I2C switches, static voltage offset sides, or level shifters)

Thanks!

Best Regards,

Comments above in BOLD.

-Bobby

Hi Bobby-san,

Thank you very much for your patient.

I'm sorry I did not understand well your idea...allow me confirm that?

Your recommendation is as below?

  CPLD --- B side(TCA9803) A side --- TCA9511A --- P82B96 --- (cable) --- P82B96

          Power : CPLD  ---   3.3V

                        TCA9803 VccB --- 3.3V, VccA --- 3.3V

                        TCA9511A --- 5V

                        P82B96 --- 5V

Best Regards,

Hi Bobby-san,

Thanks for your reply!!

I will tell your idea to the customer.

Best Regards,