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Original question:

TPS3803: Adding Hysteresis in TPS3803-01

TPS3803: Adding a hysteresis

Vladimir Naumenkov
Prodigy 120 points
Part Number: TPS3803
Other Parts Discussed in Thread: TPS3808

Dear Sir, please answer

I need to add a hysteresis in TPS3803-01. Power supply is 3.6 – 2.4 V. I need to set a threshold voltage 2.7 V and to add a hysteresis.

I use TPS3808 application, as I assume, that the logic of operation of these microcircuits is the same. (in my case V1 = V2, please, see figure 1, page 2 of TPS3808 application). On the page 4 assigned the following values: V1+ = 2V, V1- = 1.8V. 

 Please see Figure 2 of TPS3808 application, page 2:

R1 connected to V1+ voltage (it's 2V in this example).  

If I understand right, RESET output  must be HIGH at V1+ (it's 2 V ), but according to Figure 2 - this is a LOW level. And in figure 3 (page 3), in my opinion, it should be the other way around. I understand that, if the input voltage is only applied and it starts to grow, then RESET output  is LOW, until the supply reaches 2 V, but Figure 2 shows the voltage V1+ =2V, i.e. voltage at which the RESET output must be HIGH.  Please, explain.

TIA

Sincerely,

Vladimir Naumenkov

TPS3808 application_.pdf

  • +1
    TI__Mastermind 24260 points

    Hi Vladimir,

    Figure 2 describes the situation when V1 is recovering from an undervoltage condition (V1 < V1+, V1 increasing after V1 < V1-). Thus, the RESET output is still LOW.

    Figure 3 describes the case when V1 is still above V1- and has not triggered an undervoltage condition yet. Thus, the RESET output is HIGH.

    If the trends in these two situations continued until after the respective thresholds had been crossed, then your analysis would be correct. However, the figures describe situations where V1 is going towards V1+ from an undervoltage condition (Figure 2) and where V1 is going towards V1- from the nominal voltage level (Figure 3).

    Does this answer your question?

    Thanks,

    Patrick

  • +1 in reply to Patrick Shalton
    Prodigy 120 points

    Dear Patrick, thank you

    Sincerely,

    Vladimir Naumenkov