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TPS7A4001: UVLO threshold/hysteresis

ArTzy
Mastermind 20310 points

Part Number: TPS7A4001

Hi Experts,

We'd like to ask assistance for contirmation on the follow query from customer:

This datasheet declares the presence of undervoltage lockout functionality.
As far as I understand, the desired threshold is set via EN pin.
Section 6.5 (Electrical Characteristics) gives the following values ​​for VEN_HI/VEN_LO: 1.5/0.4 V.
So, ratio is 3.75, which is practically unusable, the hysteresis is very huge.
So, I think something is phrased unclearly there.

On the other hand, there is also Figure 9 (Enable Threshold Voltage).
The values ​​there look like valid hysteresis.
But that's just a graph demonstrating a typical temperature dependence.
There are no numerical values ​​that take into account factory inaccuracy/etc.

Please provide the actual VEN_HI/VEN_LO values ​​with tolerances.

Thank you.

Regards,
Archie A.

  • 0
    TI__Expert 4180 points

    Hi Archie,

    Yes this part has UVLO but the UVLO threshold is not "set" by the EN pin. The threshold is hard programmed into the device to be below the minimum recommended input voltage on the part, as described in the UVLO section in the datasheet (See below excerpt from datasheet). The EN pin is only responsible for enabling or disabling the device.

    The VEN_HI and VEN_LO thresholds are spec'd as worst case scenario voltages needed to turn the device on and off respectively, across temperature and process variations. For example, this part specs VEN_HI as 1.5V. If you apply 1.5V to the EN pin, then we are guaranteeing that the device will turn on across any and all operating conditions and process variations. The typical value needed to turn on the device may be lower than this but we can only guarantee it turning on at 1.5V or greater. Similarly, for VEN_LO, bringing this chip below 0.4V will guarantee that the device turns off across all temperature and process variations.

    It looks like this chip does have EN hysteresis of ~150mV.

    Best,

    Aden

  • 0 in reply to Aden Taylor
    TI__Mastermind 20310 points

    Hi Aden,

    Thanks for your guidance.

    Customer bought TPS7A4001 from Digikey, reported that it does not turn off the output (which is what the concept of UVLO means) if the input voltage is less than 7 volts; and it does not turn off even when it is less than 6 volts, etc. Thinking that threshold adjustment is done via the EN pin.

    So how should we perceive this? That TPS7A4001 doesn't have UVLO functionality at all?

    Thank you.

    Regards,
    Archie A.

  • 0 in reply to ArTzy
    TI__Expert 4180 points

    Hi Archie,

    This chip does have UVLO, though it appears that the typical threshold is ~3V. There is quite a large swing on this value though, so you could see maybe a volt or two above or below this typical value. The EN pin does not adjust this threshold at all, it is only responsible for enabling and disabling the device once enough voltage is supplied to pass UVLO.

    Best,

    Aden