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REF2033: Problem with the EN pin of REF2033

Fabio Lo Gerfo
Prodigy 30 points
Part Number: REF2033

Hi, I would like a technical support for my application.
In my application i use a REF 2033 with Vin=5V and I would like enable/disable it using a programmable system.
On the datesheet i see that the device is in shutdown mode (EN = 0) when 0 <= Ven <= 0.7 and the same is in active mode (EN = 1) when Ven > Vin-0.7.

I tried to anable/disable REF2033 with an FPGA with 3V3_LVCMOS output directly connected to EN pin and this (REF2033) works righ.

But if Vin - 0.7V = 4.3V is greater than 3.3V, this shouldn't turn on. Why does it occur?

Thanks for your help.

  • 0
    TI__Mastermind 19550 points

    Hi Fabio,

    The voltage between VIH (Vin - 0.7V) and VIL (0.7V) is a grey area where the EN characteristics are not guaranteed. We recommend to always go above VIH and below VIL to ensure proper operation.

    I would not consider the area between VIH and VIL as hysteresis but instead as a grey zone.

    What is the purpose of the REF2033? Do you also use the 1.65V rail?

  • 0 in reply to Marcoo Z
    Prodigy 30 points

    Hi Marcoo,

    Thanks for your help.

    I understood that the zone between VIH and VIL is not the standard hysteresis but a zone whose functioning cannot be defined.

    The REF2033 in my application is used as a voltage reference for a calibration pulse generator in a cubesat and i also use the 1.65V rail.

    If I wanted to drive the enable pin with 3V3_LVCMOS, what would you advise me to do? Can I use a MOS driven by the 3V3 rail and connected in pull up with Vin?

  • 0 in reply to Fabio Lo Gerfo
    TI__Mastermind 19550 points

    Hi Fabio,

    I agree with you, I would use a mosfet with a resistor to level shift. Keep in mind that this inverts the logic so make sure you take that into account.

  • 0 in reply to Marcoo Z
    Prodigy 30 points

    Hi Marcoo,

    I have got last questions. Is REF 2033 still in production? How long will it still be available?

    Are there any new products with similar features that can replace REF2033?

    Best regards

    Fabio

  • 0 in reply to Fabio Lo Gerfo
    TI__Mastermind 19550 points

    Hi Fabio,

    This device is in a common process, it is widely used by customers, and TI fully expects this devices to be available for the next 8-10 years and longer. TI has no plans to obsolete the device, and TI does not obsolete devices when there is still customer demand.  If there is any unforeseen issue that prevents TI from continuing to build this product thus forcing TI to obsolete this device, the customer will be given 1 year to place LTB orders and another 6 months beyond that to take final deliveries.

    There is currently no other VREF in our portfolio that can support 1.65V output. If you need 1.65V then you would have to use a voltage divider + op amp combination with a VREF.