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TPIC71004(Squib driver)_1 _ Truebeyond

dong soon Lee
Prodigy 30 points


Dear Helper,

One of our valuable customer has been developing AHLS of Vehicles with TI, TPIC71004

Below questions from the customer.

1. What's the use of SQREF1(I/O# 13) and SQREF2(I/O# 14)?  

  Please see the below.

  We are refering TI datasheet 'SLVSAR0' and the question is for 'Diagnostic Test'

 - On the 'Electrical Characteristics',  RSQRUB=1.7 to 6.5 ohm,

 - On the 'Table 3 and 4', SQUIB RESISTANCE RSQUIB = 0 to 6 ohm

 - But On the 'Table 12', Measurement Reference Resistor for SQREF1 and SQREF2 is '1K ohm'

    -> We would like to know the reason why '1K ohm'

 

Thanks

 

Kevin / Truebeyond

kevin@truebeyond.co.kr

  • 0
    TI__Guru 74322 points

    Hey Kevin,

    SQREF1 and SQREF2 are pins used as reference to calibrate the ASIC for the squib. I believe an external resistor is placed here to serve as another reference to set the firing current, I will need to check with the designer to make sure that's the case.

    Rsquib is referring the equivalent resistance of the actual squib itself, as in if you measured the resistance across the squib. The different resistances are shown to give you an idea of what voltage to provide enough current to deploy the squib.

    Let me know if you need any clarifications.

    Regards,

    Eric

  • 0 in reply to Eric Hackett
    Prodigy 40 points

    Hi Eric,

    Thanks for your reply.

    Did you check the above with the designer to make sure that's the case?

    Thanks

     

    Kevin / Truebeyond

    kevin@truebeyond.co.kr

  • 0 in reply to Tommy Lee1
    TI__Guru 74322 points

    Hey Kevin,

    I talked to the designer, and the 1k ohm is there to show that it can be supported by this part. In some vehicle systems, there is a 'buckle switch' for seat belt buckles, that when open, causes there to be a higher ohmic path for the squib. This higher ohmic path is used to calibrate the gain within the ASIC since there are multiple loops of squib resistance. When this switch is closed, the typical 0-6 ohms resistance is seen, and that's why those values are recommended.

    The 1k ohm is just there to show that it's supported, but the typical squib resistances are around 4-6 ohms, as listed in the datasheet.

    Regards,

    Eric