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REF35: About VDO

user5163865
Genius 3800 points
Part Number: REF35

Tool/software:

Hi,

If the VIN voltage falls below VDO + VREF, will VOUT be output? Or will the output stop due to an error?

VDO varies depending on the conditions, but for example, if the current VDO is 0.1V and the REF3525 is used, a minimum VIN of 2.6V is required.

In this case,
what happens when VIN = 2.55V or VIN = 2.0V?

My guess is that
when VIN = 2.55V, VOUT is approximately 2.45V.
When VIN = 2.0V, does VOUT output stop?

On the other hand, the customer believes that output stops under both of the above conditions.

Sorry for the basic question, but I would appreciate your answer.

Best regards,
Hiroshi

  • 0
    TI__Expert 6640 points

    Hi Hiroshi-san,

    We cannot guarantee device behavior if VDO specifications as reported in the datasheet are not met. Why is the customer trying to supply REF35 with an input voltage less than VDO + VREF?

    Thanks,

    Jackson

  • 0 in reply to Jackson Wightman
    Genius 3800 points

    Hi Jackson-san,

    Thank you for your quick reply.
    Initially, I told the customer that it was not guaranteed either.

    Normally the recommended operating conditions are followed, but they are checking because it is necessary to stop the output in the event of a system malfunction.

    Looking at the internal block diagram of the REF35, there is an EN control in the digital core.
    The customer speculates that this circuit will disable the device and turn VOUT OFF if VDO falls below the specified value.

    If this is incorrect, they are considering reviewing the system, so I would appreciate any advice you could give me.

    Best regards,
    Hiroshi

  • 0 in reply to user5163865
    TI__Expert 6640 points

    Hi Hiroshi-san,

    The datasheet specifies which levels on the EN pin will lead to an on or off state:

    To turn the device off, the EN pin should be at 0.3*VIN, so the customer's understanding is not correct.

    Could the customer toggle the EN pin from another source, like an MCU?

    Thanks,

    Jackson

  • 0 in reply to Jackson Wightman
    Genius 3800 points

    Hi Jackson, Thank you for your reply.

    I asked the customer to externally control the EN pin from the microcontroller.

    This issue has now been resolved.

    Best regards,
    Hiroshi