• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 35 subscribers
  • Views 1110 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.

UCC21520: VCCI terminal voltage

tateo yamashiro
Guru 10890 points

Part Number: UCC21520

Hi,

We got a question from customer about UCC21520.
Could you help us?

[Question]
Our customer is considering VCCI voltage, 3.3V or 12V. They are concerned about heat of the IC.
If internal LDO is included in VCCI terminal, power loss generates the heat. So 3.3V might be better. But 3.3V is close to minimum reccomended input voltage.
Does the IC have internal LDO in VCCI terminal? And does the condition of 12V input voltage generate the heat more than 3.3V input voltage?

Best Regards,
tateo

  • 0
    TI__Intellectual 2805 points
    Hi Tateo,

    Thank you for using the UCC21520. I am an applications engineer for this device.

    Let me look into your question and I will get back to you.

    Regards,
    Mateo
  • 0
    TI__Mastermind 23215 points
    Hello Tateo,
    Thank you for supporting the UCC21520 with your customer.
    The operating current of VCCI is not a significant consideration in power dissipation since it is only 2mA. So at 3.3V the consumption will be 6.6mW and at 12V the consumption is 24mW.
    This is only approximately a 17mW difference in power dissipation, so I would use the VCCI bias that is most convenient for the customer, and is higher than the INA and INB input signals. The VCCI bias needs to be equal to or higher than the input signal positive peak voltage.
    Please confirm on the E2E thread if this answers your questions.
    Regards,
    Richard Herring
  • 0 in reply to Richard Herring
    Guru 10890 points

    Hi, Thank you for your reply. Let me make sure one thing.
    Why does the VCCI voltage need to be higher or equal to input signal(INA,INB) positive peak voltage?

    Best Regards,
    tateo

  • 0 in reply to tateo yamashiro
    TI__Mastermind 23215 points
    Hello Tateo,
    I hope the previous answer helps your concerns.
    For the VCCI voltage needing to be higher, or the same as the input voltage; this is stated in section 6.1 in the datasheet Abs Max Ratings.
    The reason is the input signals have diodes coupling to VCCI to share the ESD protection. Therefore there is a diode path to VCCI which is not intended to sustain long time period currents flowing from input pins to VCCI.
    With the VCCI range being very wide from 3.3V to 18V this should not be a limitation in the designs.

    Regards,
    Richard Herring