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SN65HVD72: SN65HVD7x: Clarification on ±100 V transient pulse rating in Absolute Maximum Ratings

Guilherme Frantz
Prodigy 10 points

Part Number: SN65HVD72
Other Parts Discussed in Thread: THVD1400, TPD1E10B09,

Hello! I have a question regarding the absolute maximum ratings of the SN65HVD7x family.
In Table 7.1 (Absolute Maximum Ratings), the datasheet specifies:

“Voltage input range, transient pulse, any bus pin (A, B, Y, or Z) through 100Ohm: ±100 V”

However, the characteristics of this transient pulse are not defined (e.g., waveform, duration, rise/fall time, repetition rate). Right below, the datasheet lists ESD and EFT robustness levels (IEC 61000-4-2, IEC 61000-4-4, etc.), but these appear to be separate standardized tests, and it is unclear whether they are directly related to the ±100 V transient pulse condition. Could you please clarify:

1- What pulse definition (waveform and timing) is associated with the ±100 V transient rating (e.g., rectangular pulse, IEC surge-like waveform, etc.)?
2- What is the maximum allowable duration and energy for this pulse condition?
3- Is this rating derived from or equivalent to any standard test (ESD, EFT, surge), or is it an internal characterization?
4- Should this condition be interpreted as a single-event survivability limit, or is there an allowable repetition profile?

This clarification is important to understand how this rating should be used when designing external protection (TVS, series resistors, etc.).
Thanks in advance for your support.

  • 0
    TI__Mastermind 28172 points

    Hi Guilherme,

    Thanks for reaching out on E2E. Since this is somewhat of an older transceiver, we don't include much information for this spec. Let me ask around internally to see what I can find for you.

    However, if this is a new design, I would highly recommend looking at our newer THVD1400 transceiver. This transceiver has improved performance and features across the board, while being cheaper. But if you need higher bus fault protection on the differential pins, our THDV24xx series of transceivers would be best: particularly THV2410 which has +/-70V protection (sustained voltage, not a transient). We also have transceivers with surge protection build in: https://www.ti.com/product-category/interface/rs-485-rs-422-transceivers/products.html#2192=Surge%20protection& 

    For external protection, ideally you will want to spec the diode clamping voltage below the transceiver bus fault voltage. SN65HVD72 has a bus fault rating of 16V, so a clamping voltage below that would be the target. So something like our TPD1E10B09 would work well. For series resistors, I don't typically recommend these as they aren't that helpful for reducing transients, and they decrease the RS-485 drivers output strength. 

    Best,

    Ethan

  • 0 in reply to Ethan Sempsrott
    TI__Mastermind 28172 points

    Hi Guilherme,

    Below is the definition of the 100V transient. This is close to a surge test (like IEC 61000-4-5). However, to select the correct TVS/ESD diode, my comments above still apply. 

    Best,

    Ethan