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TPS3842-Q1: How to calculate hysteresis accuracy

Kazuki Kuramochi
Genius 9040 points
Part Number: TPS3842-Q1
Other Parts Discussed in Thread: TPS3760-Q1

Tool/software:

Hello Expert,

Could you please tell me how to use following hysteresis information?

Datasheet said as below.

However, this calculation seems that there are some miss match against other reset ICs and specification.

For example, to estimate min value, it probably used 5% as 7mV - 7mV*5% = 6.65mV.
If I used 0.5%, at least it should be 7mV -7mV*0.5% = 6.965mV.

Moreover, the other reset ICs hysteresis "accuracy" information is defined as below.

Then, hysteresis min/Max is calculated as Hysteresis voltage(Vth[mV]*hys[%]) * Accuracy(e.g.7mV*(+-1.5%) = 6.895mV/7.105mV).

But TPS3842-Q1's hysteresis calculation is completely different against the other device.
So I'd like to make sure about how to calculate hysteresis min/Max.

Best regards,
Kazuki Kuramochi

  • 0
    TI__Expert 6130 points

    Hello Kazuki

    I will look into the calculations, I will respond with an update by Friday 7/5

    Regards, 

    Oscar Ambriz 

  • 0 in reply to Oscar Ambriz
    TI__Expert 6130 points

    Hello Kuramochi-san, 

    Regarding the first part of the questions, it appears there is a typo. As you mentioned the following is accurate "If I used 0.5%, at least it should be 7mV -7mV*0.5% = 6.965mV." I will inform our team to complete the datasheet update. 

    Additionally, i see there is reference to another device but i do not believe it is listed. Can you tell me what the other device is? 

    Regards, 

    Oscar Ambriz 

  • 0 in reply to Oscar Ambriz
    TI__Genius 9040 points

    Hello Oscar-san,


    I understand that the calculation at datasheet is typo.
    Could you  please tell me when will you update this typo ?

    For the comparison against other device, could you confirm following comparison between TPS3842-Q1 and TPS3760-Q1?
    Both device are battery voltage monitoring, sense pin separated, reset IC.

    Left side is TPS3760-Q1's datasheet and which is defining Hysteresis "accuracy" by "-"1.5%(min) ~ 1.5%(Max). Also the other device's has almost same description. 
    On the other hands, at right side TPS3842-Q1, it is specified as Hysteresis "Voltage" as  0.5%(min) ~ 1.5(Max).
    So there are difference against previous devices.
    Therefore, I'm asking about whether TPS3842-Q1's description correct when I compare with other devices.

    Best regards,
    Kazuki Kuramochi

  • 0 in reply to Kazuki Kuramochi
    TI__Expert 6130 points

    Hello Kazuki, 

    I have informed the team of the typo and this issue will be resolved on the next datasheet revision during early Q4. 

    Yes, the way hysteresis is listed in the datasheets is different but they are both correct for their respective device. 

    Regards, 

    Oscar Ambriz 

  • 0 in reply to Oscar Ambriz
    TI__Genius 9040 points

    Hello Oscar-san,


    Thank you for your reply.

    If TPS3842-Q1's hysteresis range only have positive value, unlike other reset IC, it should be below.
    min = 700mV(Vth(typ)) + 700mV*0.01(Hys) + 700mV*0.01*0.005(Hys variation) = 707.035mV
    Max= 700mV(Vth(typ)) + 700mV*0.01(Hys) + 700mV*0.01*0.015(Hys variation) = 707.105mV

    The datasheet calculation is as below.(typo is corrected)
    min = 700mV(Vth(typ)) + 700mV*0.01(Hys) + 700mV*0.01*-0.005(Hys variation) = 706.895mV
    Max= 700mV(Vth(typ)) + 700mV*0.01(Hys) + 700mV*0.01*0.015(Hys variation) = 707.105mV

    Therefore, I'm asking you about the difference of TPS3842-Q1 and other reset IC.

    This is just confirmation and sorry for asking you again but could you please tell me which is correct calculation for hysteresis voltage?

    Best regards,
    Kazuki Kuramochi

  • +1 in reply to Kazuki Kuramochi
    TI__Expert 6130 points

    Hello Kazuki, 

    No need to apologize i'm happy to help. The hysteresis inaccuracy is only positive, your first calculation is correct. I have informed the engineer in charge of this device and he will make this update next month. 

    Regards, 

    Oscar Ambriz 

  • 0 in reply to Oscar Ambriz
    TI__Genius 9040 points

    Hello Oscar-san,


    Thank you for your support and I understand.
    I don't have additional questions any more.

    Best regards,
    Kazuki Kuramochi