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WEBENCH® Tools/TPS5401: TPS5401 using for Inverting topology

Rohidas Sawant76
Intellectual 370 points
Part Number: TPS5401
Other Parts Discussed in Thread: DAC7760

Tool/software: WEBENCH® Design Tools

Hello Sir,

  In one of our design we are going to use TPS5401.

Design requirements are as follows:

Requirement 1:

Vin= 15 to 40V

Vout=  +12V (Buck topology)

Iout=  150mA

Requirement 2:

Vin= +12V

Vout=  -12V (Inverting topology)

Iout=  30mA

I have got design calculations for Buck topology using TPS5401 from datasheet and application note.

Not, cleared about design calculations for Inverting topology as per above requirements.

I have checked for WEBENCH  tool also but did not found sample design there.

So, please support to calculate Output inductor and Output capacitance required for Inverting Topology.

 

  • 0
    TI__Mastermind 22301 points

    Rohidas,

    For detailed calculations, check out the below app note.

    http://www.ti.com/lit/an/slyt286/slyt286.pdf

     

    Luckily we have a reference design exactly for this application, check out PMP7330.

    https://www.ti.com/tool/PMP7330

    Hope this helps,

    -Orlando 

  • 0 in reply to Orlando Murray
    Intellectual 370 points

    Hell Sir,

    Thanks for reply.

    Our design requirement: We want to generate dual supply i.e. +12V and -12V for DAC7760 IC. In our design there are Two DAC7760 IC. Both this DAC will be configured for 0 to 20 mA OR +10V to -10V output mode. For this dual power supply  +12V output current requirement considered is max 70mAmp and for -12V output current requirement considered is max 30mAmp.  Pls. find attached schematic for more detail

    Query 1:

    We are looking for Inverting power supply for lesser output current ( i.e. less than -30mA) in this case it is possible that efficiency will go down and switcher will start heating due to lower efficiency. So,

    1. As per TPS5401 datasheet it has Eco- mode control for lower output current . So, will it  resolve issue of more power dissipation for lower load  ??

    2. And please guide to calculate power dissipation   for inverting topology using TPS5401 .

    Query 2:

    At the time of design, we already referred PMP7330  application note +12V Input to -12V output design. But it is for 100mA current output. Our  -12V output current requirement is 30mAmp.

    Our query are as below:

     -- is Inductor and capacitor values for 100mAmp and 30mAmp current output design will be same or different. 

     -- If we use 100mAmp design components for 30mAmp requirement, then what will be impact on efficiency and power dissipation.

     

    Query 3:

    Also we have one more query:

    1. For -12V output generation, if we externaL24V DC supply instead of +12V DC, then what will be impact on component values, efficiency  and power dissipation ?

  • 0 in reply to Rohidas Sawant76
    TI__Mastermind 22301 points

    Rohidas,

    The Eco-mode in this part is a form of discontinuous conduction mode, which will be certainly higher efficiency than converters running in continuous conduction mode for lower currents.

    However Eco-mode reduces switching frequency, making it hard to calculate exact power losses in light load.

    Calculating continuous conduction mode power losses is similar to section 8.2.2.12 in the TPS5401 datasheet, however for conduction loss and switching loss you must replace the buck IOUT with inverting buck-boost IL(avg) and the buck duty cycle with the buck-boost duty cycle provided in the previous appnote. 

    http://www.ti.com/lit/an/slyt286/slyt286.pdf

    The gate drive losses and supply losses will be the same.

    If you use the 100mA design it will just operate in eco-mode (DCM). For a 30mA design you can increase inductance by 3x to decrease ripple current. This would lead to better efficiency at light load but will slow down control loop response.

    Using a 24V supply then you should resize inductor and ripple current again.

    Hope this helps,

    -Orlando