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TPS63002: Circuit configuration for starting up with an input voltage of 3.6V

Part Number: TPS63002
Other Parts Discussed in Thread: TPS63802, TPS3803

Dear all,

I would like to ask a quesiton about this device

Our customer is planning to start with an input voltage of 3.6V with the following circuit diagram (R3 = R4 = 2kΩ).

However, when checking the data sheet, the threshold value at which EN goes high is min1.2V, and the voltage applied to the VINA pin UVLO is max1.8V.

In other words, EN goes high first, but then VINA is at UVLO. Is there any problem in this case?

If there is a problem, it is considered to set R3 = 4kΩ and R4 = 2kΩ as shown in the following circuit. With this circuit,

I think that the input voltage starts up at 3.6V without any abnormality. Please let me know if there are any problems.

Best Regards,

Y.Ottey

  • Hello,

    and thank you for using our device!

    May I ask, what is the reason for the voltage devider at VINA/EN/PS ? Do you want the device to start at VIN=3.6V?

    According to the datasheet the max threshold for VINA is 1.8V, correct. With your chosen devider you will be too close to the threshold and risk to get unwanted shutdown and restart events. You need to consider the resistor accuracy, as well.

    Regards,

    Moritz

  • Dear Moritz

    Thank you for your reply.

    I answer the following contents about your question

    "May I ask, what is the reason for the voltage devider at VINA/EN/PS ?"

    I think they are designing with reference to the configuration in the datasheet.

    Is it possible to recognize that the reference circuit example in the data sheet is valid only when using a lithium battery?

    "Do you want the device to start at VIN=3.6V?"

    Yes.

    Regards,

    Y.Ottey

  • Good morning,

    The typical application shown in the datasheet recommends a low pass filter at VINA/EN/PS, like in section 8.2 in the datasheet. If exchanging R4 with a capacitor is an option for your customer, start up at 3.6V will not be an issue anymore.

    According to the description in the datasheet section, this aplication example is suitable for "for systems powered by one-cell Li-ion or Li-polymer battery with a typical voltage between 2.3 V and 4.5 V. They can also be used in systems powered by a double or triple cell alkaline, NiCd, or NiMH battery with a typical terminal voltage between 1.8 V and 5.5 V"

    Hope this helps.

    Regards,

    Moritz

  • Dear Moritz

    Thank you for your reply.

    Does the above refer to the following circuit configuration?


    As I wrote in the first one, is there any problem with R3 = R4 = 2kΩ?

    Best Regards,

    Y.Ottey

  • Hi Y.Ottey,

    yes. However the circuit in your picture has the modification that the suggested C is changed to R4.

    With the voltage devider of 2 you will get 1.8V +- 'error' at VINA. 1.8V being the threshold of the undervoltage lockout for VINA you might not get out of undervoltage lockout or recycle your device uncontrolled, so yes, it'll be a problem.

    Regards,

    Moritz

    .

  • Dear Moritz

    Thank you for your reply.

    With the voltage devider of 2 you will get 1.8V +-'error' at VINA.
    1.8V being the threshold of the undervoltage lockout for VINA you might not get out of undervoltage lockout or recycle your device uncontrolled.
    The above problem you are worried about, I think that the following circuit (starting with Vin = 3.6V) can solve it.

    Is there anything wrong with this circuit?

    Regards,

    Y.Ottey

  • Hi Y.Ottey,

    no, that circuit will make it worse. With this voltage devider you will get 1.2V at EN, which is exactly it's threshold. This will cause the same effect as described above.

    And you're missing the filter circuit on the input of VINA, which is necessary to reduce the noise at that pin.

    Why do you need the voltage devider and cannot use the circuit show here?

    regards,

    Moritz

  • Hi Y.Ottey,

    The EN pin threshold of the TPS63002 can be anywhere between 0.4 V and 1.2 V, and cannot be used to precisely define the turn-on input voltage. Using the above approach with a voltage divider, your Vin threshold can be anywhere between 1.2 V and 3.6 V, which is not really precise.

    The TPS63802 has a precise EN pin threshold, and can be used as described in this application note:
    http://www.ti.com/lit/an/slvae79/slvae79.pdf

    If you want to use the TPS63002, you need to add a voltage supervisor circuit (such as TPS3803 for example) connected to EN pin to turn on the device at precisely Vin = 3.6 V.

    Best regards,
    Milos