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TIDA-01167: ISO7637-2 pluse 1 negative in input side

user4979989
Intellectual 2800 points
Part Number: TIDA-01167

Hi team,

Could you help to confirm and clarify my understanding and questions as below about ISO7637-2 pluse 1 figure 26 and 27.

If there is a negative spike in input side (figure 26), the reverse polarity component Q3 will conduct and short Gate/Source of Q1 and Q2 to make them switch off to disconnect input and output.

Why the output is clamped in -3.25V?

Why the input is clamped in -20V?

Once there is a negative spike in input, I have the concerns on GATE pin and OVP pin, please help to clarify if these pin are over negative voltage spec.

Please also help to confirm my understanding on SEN/VIN/UVLO/EN pin.

1. SEN pin, a zener D4 will be forwarded and make SEN pin to be Vf (0.3V-0.4V), or even without zener, SEN pin can sustain -25V as datasheet 6.1 note#5.

2. VIN pin, a diode D5 will block the negative spike and won't let the spike go into VIN pin.

3. OVP pin, if a negative spike happens, the rating has only -0.3V which is not enough?

4. UVLO pin, same as #2, D5 will block the spike.

5. EN pin, same as #2, D5 will block the spike. 

6. GATE pin, I have no idea what's the voltage on GATE pin will be, please help to clarify.

Many thanks for your help.

Regards,

Allen

  • 0
    TI__Expert 5130 points

    Allen, hello and good day.  The design owner on our Automotive Systems team is out of the office this week on holiday.  He will be able to review and provide a response to you as soon as he returns to the office on Monday, August 19th. 

    Best Regards,

    John Fullilove

    Reference Design Operations

  • 0 in reply to JohnFullilove
    TI__Intellectual 2800 points

    Hi team,

    May I have your help to check my questions?

    Thanks.

    Regards,

    Allen

  • 0
    TI__Prodigy 440 points

    Hello Allen,

    Negative voltage clamping at input and output purely depends on impedance's of pulse generator and Input impedance of TIDA-01167 and its output impedance.

    As mentioned in user guide, ISO7637-2 Pulse 1 is applied on passive board with out any load.

    1) Negative voltage at Input of TIDA-01167: With out load of TIDA-01167, ISO7637-2 pulse 1 goes to -150V. With Impedance of TIDA-01167 same pulse is clamped at input to -22V(D1 clamp).

    2) Negative Voltage at output of TIDA-01167:  TIDA-01167 has inbuilt reverse polarity protection. ISO7637-2 pulse 1 is tested under no load conditions,Due to parasitic s under no load conditions output voltage is seen dropping to -3.25V in figure 27. But it is quite sure behavior of circuit will be different in loading conditions.

    Most of your understandings are correct, circuit has been built to protect from transients mentioned in user guide.

    Thanks

    Regards

    Rama