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tpic6a596 galvanic isolation

Denis Denis36
Prodigy 170 points
Other Parts Discussed in Thread: TPIC6A596, TPIC6C596, ISO7140CC, SN74ALVC244

Dear TI-er, I have questions.

1. Has tpic6a596 any galvanic isolation between logic part and power part?

2. Do I need to use additional protection with tpic6a596 such as optocoupler?

3. Is it safety to use cascade with many tpic6a596 in commercial using to drive solenoids in fountain?

  • 0
    TI__Expert 5380 points

    1, There is not any galvanic isolation between logic part and power part, 

    2, It depends on the system requirements, adding opto-coupler between logic input and TPIC6C596 can protect the logic control input circuit.

    3, TPICA596 supports cascading connection. May I know the number of the cascading devices and the max clock frequency?

  • 0 in reply to Anda Zhang
    Prodigy 170 points

    Hi Anda Zhang!

    2, if there will not be opto-coupler between logic input and TPIC6A596 will it safety for microcontroller and other cascaded TPIC6A596?

    3. 8 TPIC6A596 per meter. max 7 meters. max clock frequency 2M. Max switching frequency in drains 100Hz

    4. if power's part transistors will be broken becouse of high voltage is there any protection of logic inputs? i.e. if TPIC6A596 will be broken is there any protection of inputs CLK, DATA and so on ? or damage of one TPIC6A596 can affect all others cascaded TPIC6A596 and microcontroller and damage all?

  • 0 in reply to Anda Zhang
    Prodigy 170 points

    Hi Anda Zhang!
    Could you pls reply?

  • 0 in reply to Denis Denis36
    TI__Expert 5380 points

    Sorry for the late reply.

    2, Generally speaking, the risk is very low when using TPIC6C596 under the rated voltage and output current.

    3, Quiet long distance, recommend to add a buffer to enhance the driving capability?

    4, Possible. May I know what is the max voltage overshoot on the output pin? If the voltage is within the max rated voltage of TPIC6C596, there should not be problem. Otherwise there is protection circuit between the input logic and TPIC6C596 device.

  • 0 in reply to Anda Zhang
    Prodigy 170 points

    Hi Anda Zhang! Thank you for your reply!

    I want to use TPIC6A596, not TPIC6C596.

    Voltage is 45-48V. Current for each drain 240mA.

    Scheme is like this: MC -> Board1 -> Board2 -> Board3 and so on.

    Distance between Boards is 0,5 meters.

    Each BoardN includes 4-6 TPIC6A596.

    Protocol SPI, max clock rate 2Mhz.

    I think it's better to use opto-couple at the end of each Board and buffer/line driver at the beginning of each Board (for Clock, Data, Latch wires).

    Opto-couple will isolate, buffer will restore signals and edges after 0,5 meter transmission.

    Do you think it's ok?

    Which opto-couple and buffer do you suggest?

  • 0 in reply to Denis Denis36
    TI__Expert 5380 points
    For isolation device, , ISO7140CC can be used for SPI isolation.
    For the SPI signal, it is recommend to use a SN74ALVC244 or similar device just in front of each board. But 2MHz SPI speed is too fast, it's better to slow down to 200kHz level as there are so many boards in daisy chain connection.
    Another thing is that, since there are some many boards in series, 0.5 meter will have 0.5 ohm resistance, to avoid the level shift on the signal (which will cause the logic fault), it is better to use parallel connection of the power line on each board instead of serial connection, and put a 100ohm resistor in front of each logic input.
  • 0 in reply to Anda Zhang
    Prodigy 170 points
    Does SN74ALVC244 restore edges? May be use buffer with Schmitt trigger?
  • 0 in reply to Denis Denis36
    TI__Expert 5380 points
    That would be better. Actually the SPI speed and Ground Level play a key role in the system. Slow down the spi speed and optimize the power trace will improve the control reliability.
  • 0 in reply to Anda Zhang
    Prodigy 170 points

    Anda Zhang, thank you!