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TCA9517A: I2C Interface (Lower Voltage Level Support) Requirement

Neil Chen
Prodigy 110 points

Part Number: TCA9517A
Other Parts Discussed in Thread: LSF0002, TCA9800, ISO1640, TCA4311, TCA4307, TCA9803, TCA9511A, TCA9617B

Hi Sirs, 

Take a TI.TCA9517A to be reference, and write my design requirement as lists : 

(1) Operating supply voltage range (A-Side & B-Side) : can accept 1.8-V voltage 

(2) VOL (Low-level output voltage) : have the upper limitation is 0.4-V voltage 

Above two cases, does TI have any I2C repeater relative solution to recommend on here? Plz confirm and many tks!!

BRs

By Neil

  • 0
    Prodigy 110 points

    Hi Sirs, 

    after my evaluate, I want to change I2C/SMBus bus buffer/repeater design requirement as lists, 

    (1) Operation supply voltage (Both sides): need 3.3-V voltage 

    (2) VOL (Low-Level Output Voltage): both sides have the upper limitation is 0.4-V voltage (for max) 

    Base on the revision required, does TI have any bus buffer/repeater solution to recommend on her? 

    BRs

    By Neil

  • 0 in reply to Neil Chen
    Guru 320280 points

    What is the purpose? Are the supply voltages on both sides always the same?

    A passive translator like the LSF0002 might work.

    If you need buffering, consider the TCA9800/1/2/3; note that it has restrictions on what you can connect to the B side.

  • 0 in reply to Clemens Ladisch
    Prodigy 110 points

    Hi Clemens, 

    Here is my current design diagram, the Nv/I2C0 bus be source and expecation get the exterinal IO voltage be 5.0-V. 

    Now, the middle isolator confirm to use ISO1640 to implement, but this isolator will possible meet Nv <=> isolator VOL is too high problem. So, estimate to add I2C/SMBus bus buffer/repeater, that's my design point target. 

    Because the Nv/I2C bus need to placed external pull-high resistors and base on my survey all TI relative buffer/repeater chip, it look like these can using: 

    (a) TCA4311

    (b) TCA4307

    (c) TCA9511

    Above all, could you help to re-confirm can design-in? if not recommend, plz let me know which one be suggestion on here? Many tks!

    BRs

    By Neil

  • 0 in reply to Neil Chen
    TI__Guru 55618 points

    Hi Neil,

    I am not sure that TCA9803 will work well with the static voltage offset of the side 1 VOL output from the ISO1640. I have not seen too promising of results in the past from connecting the internal current source on B-side of the TCA9803 to an ISO1640. Not sure if this will work but it could be worth a try. I would recommend to remove any external PU resistors on B-side of the TCA9803. You could also flip the direction of the TCA9803 so that the A_side faces the ISO1640 and the B-side faces the Jetson Orin. You would need to ensure any external or internal PU resistors are removed/disabled on I2C0. 

    For the three hot-swap buffers listed: TCA4311/4307/9511, these buffers will also not work for your system. These buffers all implement some type of rise-time acceleration circuitry which means they will drive to VCC for a brief period of time under specific conditions. The conditions are a specified rising slew rate and a voltage input threshold of 0.6 V. 

    The VOL1 of the ISO1640 unfortunately is between 570mV and 710 mV with typical of 650mV. The output LOW of the ISO1640 will trigger the RTA threshold of the TCA9511A which will create problems. TCA9511A drives HIGH while the ISO1640 is attempting to drive LOW. 

    What is the VIL of the Jetson Orin Module? 

    I believe using TCA9517A / TCA9617B would also not work, since you would need to have B-side face the Jetson Orin, which VOLB = 0.52V. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 110 points

    Hi Tyler, 

    thanks for your great support and response, plz refer to my response for relative Jetson Orin Module specifcation: 

    (1) VOL = 0.3 x 3.3 = 0.99-V voltage 

    (2) VIL = 0.2 x 3.3 = 0.66-V voltage 

    Above I2C interface case of Jetson module side, and share current design series diagram by using "bus buffer/repeater + isolator" solution. 

    Plz help to review which one of TI solution can recommend on here? (for bus buffer/repeater part) Many tks!

    BRs

    By Neil

  • 0 in reply to Neil Chen
    TI__Guru 55618 points

    Hi Neil,

    So in this case, I would recommend the following: 

    Either the TCA9517A or TCA9617B can be used with its B-side facing the Jetson Orin. 

    The PU resistors will need to be adjusted to ensure that the Jetson Orin can pull LOW below a VOL = 0.4V in order to me the VILC or VILB spec of the buffers listed. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 110 points

    Hi Tyler, 

    Thanks for your update, after discussed our customer to deep dive this topic and we have an one question to asking as list, 

    As mentioned the Nvidia Jetson Orin module/ I2C interface required, is VOL = 0.99-V (possible can adjust pull-high become lower voltage) & VIL = 0.66-V, for maximum. 

    But, after reviewed you recommend "TCA9517A or TCA9617B" datasheet (as Fig.1 & Fig.2 relative VOL define), both(B-Side) look like are very close "Nvidia Jeton/ VIL required" and consider too margin for possible get "fail" judgement of Nvidia Jetson side. 

    So, does possible can find an other similar bus buffer solution to implement and VOL can be more lower required? 

    Plz confirm and need you great support on this topic, many tks!!

    Fig.1: TCA9617B/ VOL Specification

    Fig.2: TCA9517A/ VOL Specification 

    BRs

    By Neil 

  • 0 in reply to Neil Chen
    TI__Guru 55618 points

    Hi Neil,

    Those VOL's are correct from the TCA9617B / TCA9517A datasheets. 

    VOLB(max) = 0.58V

    VOLB(max) = 0.60V

    is close to the 0.66V max for Jetson Orin, but will still work. 

    If possible, you can also flip the buffer so that the A_side faces the Jetson Orin. There you have much more margin with a lower typical VOLA = 0.1 V. 

    You might consider the TCA9803 as it has low VOL on both sides. 

    The limitation with this device is that it cannot be used with 5V logic, and the device has strict limitations on the B-side which requires no external sources of pull-up current such as pull-up resistors or leaky ESD cells on the B-side. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 110 points

    Hi Tyler, 

    Tks comment, this bus buffer will implement on VCC=3.3-V voltage so can ignore the 5V logic, I still have two questions to asking : 

    1. TCA9617B/TCA9517A A_Side connect to Jetson Orin => this one can provide more lower VOL level to avoid Nvidia judgement condition occur. 

    But, other side (B_Side) connected to Isolator/ISO1640B, it will have any functional risk? Plz double confirm. 

    2. TCA9803: this one isn't a good choice to design-in, due to B-side not necessary external PU resistor and not sure affect functional behavior. 

    BRs

    By Neil

  • +1 in reply to Neil Chen
    TI__Guru 55618 points

    Hi Neil,

    Neil Chen said:

    1. TCA9617B/TCA9517A A_Side connect to Jetson Orin => this one can provide more lower VOL level to avoid Nvidia judgement condition occur. 

    But, other side (B_Side) connected to Isolator/ISO1640B, it will have any functional risk? Plz double confirm. 

    I am not so confident having B-side face the ISO1640 due to the large output low voltage from the ISO1640. The logic low cannot be interpreted by the TCA9617B/TCA9517A due to this larger voltage. 

    VILB must be < = 0.4V for TCA9617B

    VILB must be < = 0.45 V for TCA9517A

    Neil Chen said:
    2. TCA9803: this one isn't a good choice to design-in, due to B-side not necessary external PU resistor and not sure affect functional behavior. 

    I would not recommend TCA9803 for this application. 

    Regards,

    Tyler