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THVD1550: Difinition of Driver Short Circuit Current

Shinichi Inoue
Guru 22541 points

Part Number: THVD1550

Dear Specialists,

My customer is considering THVD1550 and has a question.

I would be grateful if you could advise. 

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In the datasheet P.8 of 7.6 Electrical Characteristics, Ios(Short-circuit output current) is defined -250mA to 250mA.

How should we understand this?

Which is the correct understanding？

(1) When the driver outputs A and B are short-circuited, the protection function inside the device limits Ios to the range of ± 250mA.
And since the driver is protected, it will not break down.

(2) When the driver outputs A and B are short-circuited, it is necessary to insert an external resistor so that Ios is within the range of ± 250mA.
When Ios exceeds ± 250mA, the driver may be damaged.

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I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    Guru 327300 points

    The absolute maximum ratings and recommended operating conditions are limits that your circuit must be designed to meet. The electrical characteristics describe how the device itself behaves.

    The IOS specification in section 7.6 says that if you force an active output to any voltage between −15 V and 15 V, then the current that flows is guaranteed to be between −250 mA and 250 mA.

    The IO specification in section 7.3 is ±60 mA. When you exceed it, the device might no longer work correctly. There is no absolute maximum rating for the output current, only for the bus voltage, so the current that flows for any voltage up to ±18 V will not damage the device.

  • 0
    TI__Guru 54042 points

    Hi Shinichi,

    The short circuit current is the current sourced/sunk from/into A into/from B when A and B are shorted together (with the voltage to ground being within +/-15V) will not exceed the +/-250mA boundary. It is not a design requirement but a spec on how the device operates in circuit conditions - the short circuit that we define for RS-485 is due to an insulation failure in the cable that could cause A and B to short circuit (but they could have a common mode  voltage still - which is why test to +/-15V).

    Please let me know if you have any other questions!

    Best,

    Parker Dodson