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LM3435: [ LM3435 ] SVDD Supply Range and Power Sequencing

Kenichiro
Mastermind 9165 points
Part Number: LM3435

[ LM3435 ] SVDD Supply Range and Power Sequencing

Dear forum member,

Could you help to check the supply voltage range of SVDD of LM3435?
I can find the specification for VIN, however, no clear description for SVDD range.

The information, I can find out from datasheet is below.


However, different information can be seen on the following post from Mr. Issac.

"Yes, it is ok to connect SVDD to VIN (as long as it is above 2.5 V)."

LM3435 / unused pin, control freq
e2e.ti.com/.../552806


Can you clarify the valid SVDD supply range?
Also, is there are the requirements and/or restrictions on power supply sequence between VIN and SVDD?

Thank you for your support in advance.
Regards,
Ken

  • 0
    TI__Mastermind 25500 points

    Hello Ken,

    I couldn't find clarification in the datasheet either, but Issac is the expert on this device so I have made him aware of this question. He should be able to clarify for you soon.

    Best regards,

    Clint

  • 0
    TI__Expert 3920 points
    Hi Ken,

    The previous question was asking if SVDD can be connected to VIN.
    The answer is yes based on VIN needs to be working above 2.5 V.

    The SVDD itself is independent of VIN and can be operating from 1.7 V to VIN (as long as your VIN is within 2.5 V to 5.5 V).

    Hope this clarifies your question.
  • 0 in reply to Issac Hsu
    TI__Expert 3920 points
    Hi Ken,

    One more thing, there was no sequencing as long as you tied SVDD and VIN together.
    If you separate them, it would be better to have SVDD runs up earlier than VIN.

    Thank you!
  • 0 in reply to Issac Hsu
    Mastermind 9165 points

    Hi Issac,

    Thank you for your feedback! It's clear for me.
    I will consult with my customer!

    Hi Clint,

    Thank you for your support as well!

    Regards,
    Ken

  • 0 in reply to Issac Hsu
    Mastermind 9165 points

    Hi Issac,

    Let me ask few more things with regards to power supply and its sequence.
    My customer would use the separate power supply (+1.8V SVDD and 5V VIN).  I  ask customer to ramp SVDD first, then VIN follow.
    Here are two queries.

    Q1: Are there any time/delay requirements between each ramp-up?

    Q2: Any requirements on shut-down sequence?


    Thank you for your support in advance.
    Regards,
    Ken

  • 0 in reply to Kenichiro
    TI__Expert 3920 points
    Hi Ken,

    It was not tested / specified for any timing / delay requirements between SVDD and VIN ramp-up.
    My guess is a several tens of micro-second of separation would do the job.

    Similarly, there was no shut-down sequence listed / tested.
    I would say as long as VIN goes off earlier than SVDD (by again several tens of micro-second), it will be fine.

    Thanks!