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  • TI Thinks Resolved

TLV6703: Hysteresis range

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Replies: 22

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Part Number: TLV6703

Hi Sir 

TLV6703 hysteresis range 5.5mV is too small 

May I know how to extend the hysteresis range of TLV6703 ? have any tool can easy design ?

So far our application is 2cell battery voltage monitor ,the battery voltage is 8.4V~6V

We would like to design VIT-=5.9V and VIT+=6V

Thanks 

  • In reply to Kai Hsiao:

    Hi Kai,

    I have found the recommended values in the simulation by trial and error. I just played a bit with the values. Deriving the correct formulas for the resistances consumes more time.

    The correct formulas are:

    R2 = R3 x D x (0.395V x B - 0.4V x A) / (0.4V x A x D + R3 x B x C)

    R1 = (R2 x R3 x B) / ((R2 + R3) x 0.4V)

    with:

    A = 5.95V - 0.395V

    B = 6.05V - 0.4V

    C = 5V - 0.395V

    D = R3 + 10k

    5.95V in "A" is your lower threshold. Change it as desired. 6.05V in "B" is your uppper threshold. Change it as desired. 5V in "C" is the pull-up voltage. And 10k in "D" is the pull-up resistance.

    The run of the calculation is as follows: Choose R3 arbitrarily. The higher R3 compared to R1 and R2, the lower the hysteresis. I have chosen 10M here. Then, enter R3 into the formula of R2. Afterwards, enter R3 and R2 into the formula of R1. Of course, you could create an excel sheet which does all these calculations automatically for you.

    Here is the result of the simluation with the improved values:

    And here is the according TINA-TI file:

    kai_tlv6703.TSC

    Kai

  • In reply to kai klaas69:

    Kai

    Just to be clear, when you resistor divide down your input voltage to the 0.4V reference level (approximately 15:1), that gains up the internal hysteresis of the TLV6703 by the same ratio.  So the internal hysteresis of 5.5mV becomes approximately 82.5mV without adding any feedback. 

    However, to your point we should add some equations to our datasheet to help in the design of circuits that require additional hysteresis.

    Chuck

  • In reply to Chuck Sins:

    Hi Chuck

    1. if Vih+=6.8V ,Vil-=6V ,May I know the resistor value? this application is using for 2cell battery voltage monitor 

    2. If 15:1 ratio ,the internal hys will be 82.5mV ,what's the side effect ? sorry ,i have a little confuse 

    I use kai_tlv6703.TSC to calculator ,but seems like the result is not correct 

  • In reply to Kai Hsiao:

    Hi Kai,

    I think you have made a mistake during the calculations. Applying the formulas by myself, I get:

    However, taking into account the input current of TLV6703 of up to 25nA, I would decrease these resistor values by at least a factor of 20:

    Kai

  • In reply to kai klaas69:

    Thanks Kai for your support on this.  As usual, your support is excellent.

    Kai

    Now that you are requesting much more hysteresis than 100mV, introducing positive feedback is required as Kai has shown.

    Chuck

  • In reply to Chuck Sins:

    Thank you, Chuck!

    Kai

  • In reply to kai klaas69:

    Hi Kai / Chuck

    Thanks for your fully support 

    just one question 

    how do you use TINA to calculate the value?

  • In reply to Kai Hsiao:

    If you are using TINA, then that is a trial and error approach.  Reducing the size of the positive feedback resistor will increase your hysteresis.  However, it will also slightly impact your initial switching threshold.  It is possible to fine tune your circuit with TINA but I would recommend doing some calculations so you have an expectation for your results before running your sim.

    Chuck

  • In reply to Chuck Sins:

    TLV03.xlsxhI Sir

    I follow your formulas then got R1 = 11K ;R2=4.7K ; R3 =470K 

    But got fail reslut after implemented to test , the pin allways Hi ,no chance goes to lo ?

    Could you please teach me whats problem ?

    Attached is my calculation form !!

    The correct formulas are:

    R2 = R3 x D x (0.395V x B - 0.4V x A) / (0.4V x A x D + R3 x B x C)

    R1 = (R2 x R3 x B) / ((R2 + R3) x 0.4V)

    with:

    A = 5.95V - 0.395V

    B = 6.05V - 0.4V

    C = 5V - 0.395V

    D = R3 + 10k

  • In reply to Toby Lan:

    Toby

    It appears that you are new to this thread.  Please recognize that the equations you shared have an upper threshold of 6.05V and a lower threshold of 5.95V.  I just want to make sure that you were aware of this when you ran your simulation.  If you want to change to the previous design plan of Kai which had Vih+=6.8V ,Vil-=6V, you will need to alter your equations.

    Chuck

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