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WEBENCH® Tools/LM53602-Q1: Why LM53602 can't create5vin/3.3Vout Iout 2A?

Chen Bogey8
Mastermind 9990 points
Part Number: LM53602-Q1
Other Parts Discussed in Thread: LM53602, TPS62090-Q1, TPS62065-Q1

Tool/software: WEBENCH® Design Tools

Hi Sir 

Why LM53602 can't create5vin/3.3Vout Iout 2A?

Since 5Vin is in spec range. 

And for LM53602 EVB, i also can't see the input voltage range.

                                                                    Bogey

  • 0
    TI__Guru**** 191445 points
    Moving to the Webench forum...
  • 0
    TI__Intellectual 2360 points

    Hi,

    The LM53602 family has a special FPWM operating mode when Vin is close to Vout.  This operating mode is not currently modeled in WEBENCH Power Designer.  As a workaround, you can set VinMin to 5.3V, then use the online simulation feature of WEBENCH Power Designer to observe the modeled operation at Vin=5V.

    The EVM user's guide doesn't appear to directly state the operating input voltage range for the designs.  However, the graphs in section 3.2 (for the 3.3V version) show Vin as low as 8V.  The 5V graphs (section 3.1) show Vin as low as 5.5V.

  • 0
    TI__Guru**** 150770 points
    Why are you using a 36V device for a 5V rail? The TPS62065-Q1 or TPS62090-Q1 is much smaller and more cost effective.
  • 0 in reply to Wanda Garrett - WEBENCH Design Center
    TI__Intellectual 2360 points
    Hi - a correction - the limitation is not the FPWM operating mode. Rather, the device goes into a frequency-foldback mode when Vin is close to Vout. This operating mode is not modeled in WEBENCH Power Designer, so designs are not provided for this situation.
  • 0 in reply to Wanda Garrett - WEBENCH Design Center
    Mastermind 9990 points

    dear All

    Sorry for i have some confuse, may i verify some as below:

    1. As i under stand, the LM53602 can use in 5Vin/Vout 3.3V Iout 2A pplication, am i right?

    2. My customer choice LM53602 in 5Vin application is because they have experence that IC be demage by Vin spike.

    3.I use webbench to simulation 5.3Vin/3.3Vout Iout2A, and change Cout from 22uF to 100uF, but why Cff(47pf) have no chage at the same time. but from Datasheet table 3, the Cff is usggest 120pf.

    4. may i know what is"VEN Enable input threshold voltage, Hysteresis, below min 0.45V max 0.55V"? these is no much explain in datasheet.

                                                                          Bogey

  • 0 in reply to Chen Bogey8
    TI__Intellectual 2360 points
    Hi Bogey,
    1. Yes, your design parameters are within the operating range for the device, although not within its optimum range. See the "System Characteristics" section of the datasheet (page 7), which shows that for the referenced typical application circuit, and Vout=3.3V and Iout=3A, the minimum input voltage is typically 3.9V. Regulation may not be as good at the low input voltages as it would be for the specified range of Vin>=6V (see Line Regulation in the same table). Also see Electrical Characteristics (page 6), Vin_operate (minimum operating voltage) is 3.95V at its highest.

    2. OK.

    3. When you select different components in WEBENCH Power Designs, the other components are not changed automatically.

    4. VEN has a threshold of between 1.7 and 2V, when VEN is rising. Once VEN reaches the threshold and establishes a "logic high", it needs to fall by at least the value of the hysteresis to be considered "logic low". The hysteresis has a range of 0.45 to 0.55V. See section 8.3.2 for further information about the operation of the EN input.