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TPS3806I33-Q1: TPS3806I33DBVR Hsense Lsense

John Lucas
Prodigy 20 points
Part Number: TPS3806I33-Q1
Other Parts Discussed in Thread: TPS3779, TPS3710

I am working with an TPS3806I33DBV. I am having trouble with the voltage drops across the Hsense and Lsense. In the order that they are shown in relevance to the resistor dividers on the data sheet the Lsense will always have a higher voltage than Hsense. Am I not understanding something about this or is the information perhaps incorrect? Please advise as my circuit is currently not functioning as desired and I need to eliminate or correct this possibility.

  • 0
    TI__Genius 12630 points
    John,

    The HSENSE has the higher voltage threshold since this threshold is given by V_HSENSE = Vref (R1 + R2 + R3)/R3 while V_LSENSE = Vref ( (R1 + R2 + R3)/(R2 + R3). This makes sense since HSENSE represents the falling threshold LSENSE plus hysteresis. Please refer to "programming voltage thresholds" on pg 5 of the datasheet when calculating resistor values and thresholds.

    Please click “This resolved my issue” button if the answer provided resolved your issue. If this doesn't resolve your issue, please provide a schematic of your circuit so I can better assist you. Thanks!

    -Michael
  • 0 in reply to Michael_DeSando
    Prodigy 20 points

    I appreciate the response. I have been using the equations on sheet 5. I have one additional question. Is the reference voltage on sheet 5 of 1.207 V, an arbitrary reference voltage? I am not understanding how that comes in to play seeing as systems usage vary greatly. I have used voltage divider equations with V_in @ 4.7 and my values will look much different and are closer to preventing operation during brown out.

  • 0 in reply to John Lucas
    TI__Genius 12630 points

    John,

    Reference voltage ~1.2V is standard. Reference voltages also come ~0.4V and ~0.8V and other references are offered depending on the device and the version. It all depends on the design of the internal circuitry. We have similar devices to this one but with independent sense inputs (rather than an input with adjustable hysteresis) such as TPS3779. Or a single input detector with fixed hysteresis rather than adjustable hysteresis TPS3710.

    I'm not sure I understand "I have used voltage divider equations with V_in @ 4.7 and my values will look much different and are closer to preventing operation during brown out." Please give me more information so I can help. Do you have a schematic I can refer to?

    -Michael