• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 3 answers
  • Subscribers 63 subscribers
  • Views 386 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS3850: TPS3850 - Threshold limits (min. and max.)

Nilesh Khupase
Intellectual 470 points
Part Number: TPS3850

Hello,

I am confused about the threshold limits (min/max values) of Precision window supervisor IC TPS3850G33DRC, which has been used for OV & UV monitoring in one of our existing board. As per datasheet nominal thresholds are mentioned as a percent of the nominal monitored voltage which are, VIT+(OV) = 4%; VIT–(UV) = –4% of 3.3V (nominal monitored voltage option in our case which is going to the SENSE input).

if my power supply tolerance is from, 3.207V (min.)  - 3.3V (typ.) -  3.472V (max.) then will the TPS3850 thresholds vary accordingly for overvoltage? for e.g. if in one of the scenarios my power supply is maximum (3.472V) then will the threshold values of TPS3850 be ±4% of 3.472V (max. value)?

 Thanking you in advance.

  • 0
    TI__Genius 9640 points

    Hi Nilesh,

    Thanks for your question. Please find the window comparator timing diagram below. 

    TPS3850G33DRC has a nominal threshold value at 3.3V, and it won't vary with the power supply. If you look at the diagram above you can see the voltage range that asserts and un-asserts the reset signal. And you can find the tolerances and the hysteresis. Thanks to hysteresis the reset won't be affected small changes. 

    If the Sense voltage is less than VIT-(UV) (min) = 3.3V - (3.3V x 0.8%) = 3.2736V, and over than  VIT+ (OV)max)= 3.3V + ( 3.3V x 0.8%) = 3.3264(In the datasheet  6.5 Electrical Characteristic section you can find the ranges for the parameters for VIT+(OV), VIT-(UV),  Hysteresis voltage)

    Please let me know if you have further clarifications. 

    Best Regards,

    Sila Atalar 

  • 0 in reply to Sila Atalar
    Intellectual 470 points

    Hello Sila,

    Thanks for the reply. Just correct me where my understanding is wrong. In our case, nominal monitored voltage option chosen is 3.3V  (TPS3850G33DRC) with tolerance limit of ±4%. Which gives me the nominal threshold values as VIT-(UV) = -(3.3 x 0.04) = -0.132V and VIT+(OV) = (3.3 x 0.04) = 0.132V.

    Table 6.5 'Electrical Characteristic' section gives me the min. and max. ranges for these parameters VIT+(OV) and VIT-(UV). For e.g. VIT+(OV) will vary ±0.8%, so VIT+(OV)max.=0.132 x 1.008=0.133V and VIT+(OV)min.=0.132 x 0.992=0.131V. 

    If the sense voltage is beyond this voltage range of 3.3V±0.132V, assertion of reset line will take place. These threshold values (±0.132V, ±4% of 3.3V) are fixed and will not vary with the IC Power supply tolerance.

  • 0 in reply to Nilesh Khupase
    TI__Genius 9640 points

    Hi Nilesh,

    Your understanding is correct. I just want to clear it briefly one more time. 

    The TPS3850 will not vary with the IC Power supply tolerance.

    TPS3850G33DRC has a threshold at 3.3V, and  ± 4% is the threshold that the device is actually set to.  And  0.8%  is the accuracy.

    So, for VIT+ (OV) = 3.3 +4%, and with the accuracy of 0.8%, we are accepting the trigger to happen  (3.3 +4%) ± 0.8%, and 

    for VIT- (UV) = 3.3 - 4%, and with the accuracy of 0.8%, we are accepting the trigger to happen  (3.3 +4%) ± 0.8%

    I hope it helps!

    Best Regards,

    Sila Atalar

  • 0 in reply to Nilesh Khupase
    TI__Genius 9640 points

    HI Nilesh,

    No problem!

    Regards,

    Sila Atalar