• State
  • Locked Locked
  • Replies 8 replies
  • Subscribers 83 subscribers
  • Views 498 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMDXIDDK379D: IDDK development kit LEM sensor overcurrent protection threshold

Cherry Zhou
Mastermind 22235 points
Part Number: TMDXIDDK379D
Other Parts Discussed in Thread: BOOSTXL-DRV8301, DRV8305, BOOSTXL-3PHGANINV, INA240, DRV8301

Hi team,

The customer has found some errors in our documents:

As shown above, the LEM overcurrent protection threshold is 11A. 

This section of the circuit is shown in the figure, and the sensor output at 11 A of the original side current is calculated as:

LTS 6-NP：( 11 / 3 ) * 0.625 + 2.5 = 4.792V

CAS 6-NP：11 * 2 * 0.1042 + 2.5 = 4.792V

4.792V post-stage operation requires a multiplier of 0.66, i.e. 4.792 * 0.66 = 3.16272V. This voltage value is essentially the same as the 3.1565-V threshold set by the subsequent comparison circuit:

However, for the current sensor, 4.792V is out of the linear range of the sensor output:

Issue: is there anything wrong with the LEM sensor overcurrent protection threshold of 11A described in the document?

Could you help check this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Mastermind 45426 points

    Hi Cherry,

    I am reviewing these details and will get back to you soon.

    Best,

    Kevin

  • 0 in reply to Kevin Allen18
    TI__Mastermind 45426 points

    Hi Cherry,

    What the customer mentions looks valid. The Hall sensor is getting saturated a 11A and the subsequent trip may / or may not occur (it's really on the boundary). The trip current can be set and reduced by changing the TrpRef resistor divider shown below. The MAX trip current that can be set is ideally ~10.2A with a TrpRef of ~3.05V.

    I'll submit a ticket to have the document improved.

    Best,

    Kevin

  • 0 in reply to Kevin Allen18
    TI__Mastermind 22235 points

    Hello Kevin,

    Thanks for your confirmation.

    And please also be aware of there might be some same errors we should take a look at:

    1). BOOSTXL-DRV8301: the characters of a built-in check amplifier is as follows:

    The current acquisition section is designed as follows:

    The sampling resistance is 10 mohm, the midpoint is half the AD acquisition range of 1.65 V, and the internally programmable gain of 8301 is set to 10. So the acquisition range here is 16.5A * 0.01ohm * 10 = 1.65V, which is designed to be ±16.5A for 0 to 3.3V. However, based on the output linear range of the check amplifier, the design here is also clearly outside the linear output range of the amplifier..

    2) BOOSTL-DRV8305: The current acquisition section is designed as follows:

    The sampling resistor is 7 mohm, the midpoint is half the AD acquisition range of 1.65 V, and the internally programmable gain of 8305 is set to 10. So the collection range here is 20A * 0.007ohm * 10 = 1.4V, which is designed to be ±20A for 0.25V to 3.05V.

    The DRV8305 detection amplifier's character is as the following:

    No linear region is exceeded at +20A, but at -20A, the linear region of the operational region is exceeded (less than 0.3 V).

    3) BOOSTXL-3PhGaNInv: The current acquisition section is designed as follows:

    The sample resistance is 5 mohm, half the mid-point AD acquisition range is 1.65 V, using the INA240A1 with a 20-factor ratio. The acquisition range is therefore 16.5A * 0.005ohm * 20 = 1.65V, and is designed to be ±20A for 0V to 3.3V. The VS of the INA240 in the circuit = 3.3 V.

    The output swing of the INA240 is limited by the VS, and therefore cannot meet the 16.5-A 3.3-V design.

    The problem is the same for the three development kits above, please help confirm. Thanks.

    Thanks and regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Guru* 92200 points

    Hello Cherry,

    Kevin is currently out of office.  He should get back to you at the end of the week. 

    Thank you for your patience.

    Lori

  • 0 in reply to Lori Heustess
    TI__Mastermind 22235 points

    Hi Lori,

    Thanks for your message and expect the response.

    Regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Mastermind 45426 points

    Hi Cherry,

    I am still reviewing these details and will need to get back to you soon after I have the answers.

    Best,

    Kevin

  • 0 in reply to Kevin Allen18
    TI__Mastermind 22235 points

    Hi Kevin,

    Understood and thank you.

    Regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Expert 3620 points

    Hi Cherry,

    Thank you for your patience!

    Here is the response -

    1. BOOSTXL-DRV8301 supports only upto 10ARMS (14APEAK). The current measurement is scaled for ±16.5A just to show the calculation. So actually, that output voltage will be ±1.4V will be with respect to VREF of 1.65V. Output voltage swing will from 0.25V to 3.05V. So, lower swing 0.25V will still less than 0.3V which is out of specs of DRV8301’s internal shunt amplifier. I will create the Jira ticket to improve the doc. Please note that existing current range will still work with onboard external amplifier as shown below.

    2. BOOSTXL-DRV8305 – Similar issue as mentioned in 1. I will create Jira ticket to improve the same.

    3. BOOSTXL-3PhGaNInv – Similar issue as mentioned in 1 with external amplifier INA240A. I will create Jira ticket to improve the same.

    Regards,

    Sumit Patil