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Question on TIDA-00699

Randhir Kalsi
Expert 4545 points
Other Parts Discussed in Thread: TIDA-00699, LM53603

Hello team,

Hope you are well.

Would you be able to help out with customer inquiry:

Does the TIDA-00699 operate through (5V buck output doesn’t fall out of regulation) ISO 7637-2:2004 Pulse 1, 2a, 3a/b and 5b (clamped load dump) tests?

If so by what means is the energy well used to hold up the system implemented?

  • 0
    TI__Intellectual 1930 points

    Hi Randhir,

     

    Thanks for the question. For scalability, the information from our email thread is contained below.

     

    Yes, the TIDA-00699 is designed to operate through all the listed pulses. The combination of the smart diode controller, EMI filter, TVS diodes and high input voltage devices prevent any disturbances to the system output during these pulse conditions.

     

    For pulse 1, the TVS diode clamp the pulse voltage at -21V and shunt the remaining energy. The smart diode controller (LM74610) disconnects the circuit from the input within a few us of the pulse, and the 5V output is sustained by the residual charge on the input capacitors until the supply voltage recovers. There is some undershoot on the line.

     

    For Pulse 2a, the clamping TVS diodes and damping of the input filter prevent any noticeable disturbance at the input of the upstream devices.

     

    For Pulse 3a/b, these very fast transient pulses are completely dampened by the input filter and are unnoticeable at the inputs of the upstream devices.

     

    For Pulse 5b, the voltage rise is slow enough for the control loop of the LM53603 to respond to the input voltage ramp preventing any noticeable disturbance at the output.

     

    To confirm these, please refer to the design guide.

     

    Thanks,

     

    Luis Cordova

  • 0 in reply to Luis Cordova
    Prodigy 220 points

    Specifically regarding Pulse-1 (2 mSec, -75V negative transient) I am intrigued by the statement in the design guide:

    "Though it is not shown here, the LM74610 disconnects the circuit from the input within a few µs of

    the pulse, and the output is sustained by the residual charge on the input capacitors until the supply

    voltage recovers."

    The design guide does not seem to state the load on the output during this test. From my understanding, ISO 7637-2 pulse tests require the equipment to be operating under 'normal conditions' and to be 'fully initialized'.

    As the PSU design is 10W to 15W, was the output loaded to this level during the Pulse-1 testing?

    Pulse-1 specifies that 'normal power' is not re-applied (following the pulse) until 200 mSec later (t2), and so any bulk-storage capacitors would need to support a 200 mSec power drop-out, not 2 mSec, in order to avoid crashing any connected equipment. There's not much point in holding up a supply's output with nothing connected to it!

    Regarding automotive testing, ISO-7637-2 Pulse-1 does not appear to have evolved to cope with modern automotive infotainment/communications equipment These are almost certainly running some form of operating_system / file_system, and do not take kindly to having power repetitively removed. Pulse-1 is supposed to be repeated for 500 cycles. Communications equipment could take minutes to be fully 're-initailized' before the next pulse-cycle, which potentially makes this test very time-consuming (and hence very expensive).

    Does anybody know if the 200 mSec time is allowed to be shortened? If 'normal' power was allowed to be re-applied immediately after the 2 mSec pulse, which is more representative of the real world, then the test makes more sense and equipment is not un-necessarily crashed during testing.

    Anybody any thoughts/experience of this?

  • 0 in reply to dh
    TI__Intellectual 1930 points
    Hello,

    Unfortunately, I do not currently have the information as to what is allowed in regards to power drop-out time shortening.

    As for the loading during the Pulse-1 testing, this is ultimately dictated by the amount of energy storage available. I do not have an exact figure as this was mainly done to demonstrate the device behavior during such condition.

    -Luis