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TPS61046: Webench Design Issue

Andradige Silva
Prodigy 30 points
Part Number: TPS61046
Other Parts Discussed in Thread: TPS61251, TPS61086, TPS61093

Hi,

I tried designing a boost circuit using TPS61046 with TI Webench tool using conditions Vin(min) 2.1V, Vin(nom) 2.5V, Vin(max) 2.9V, Vout 6V.  For Iout I tried 0.12A, 0.2A and 0.32A.  Webench was able to design only for Iout 0.12A. For other two Iout cases, I got following error.  Does this mean that TPS61046 cannot support 0.2A and 0.32A output currents?

  • 0
    TI__Expert 4750 points

    Hi Andradige,

    It's a valid fail. Device TPS61046 for Vin(min) 2.1V, Vin(nom) 2.5V, Vin(max) 2.9V, Vout 6V and Iout of 0.13A has peak switch current of  0.543A as shown in image1 below.

    For mentioned Vin, Vout condition, with any Iout greater than 0.13A device will hit peak switch current limit of 0.6A as per datasheet as shown in image 2 below.

    Image 1

    Image 2

    Thanks and Regards,

    Umayal

  • 0 in reply to Umayal Ramanathan
    Prodigy 30 points

    Hi Umayal,

    Thank you for the quick response.  As specified in the datasheet, 600mA is the minimum, 900mA is the nominal and 1200mA is the max for peak switch current.  Shouldn't the Webench allow at least the nominal case and perhaps even up to 1200mA?

  • 0 in reply to Andradige Silva
    TI__Expert 3320 points

    Hi Andradige,

    No. We should not allow Webench to go upto 1200mA. There is possibility that even if we allowed the designs on simulation tool, it might fail on board. Due to this Webench has standardized to use minimum value of current limit to avoid suggesting incorrect designs. 

    That being said there is not much difference between two input conditions (Iout 0.12/0.2/0.32) and same external components might be used for testing as that of 0.12 design. I will suggest using Webench power designer tool to get the working solutions for your input condition (below steps).

    VinMin=2.1V, VinMax=2.9V, Vout 6V, Iout=0.2

    1. Click on below link.

    https://webench.ti.com/power-designer/switching-regulator

    2. Enter your inputs as shown below and click on view designs. From the solutions listed filter out the one which works for you. 

    Best Regards

    Bhushan 

  • 0 in reply to Bhushan Waghmare
    Prodigy 30 points

    Hi Bhushan,

    Thank you for your response.

    For Iout = 0.2A Webench failed before but Iout=0.12A worked fine.

    If I create a Webench design with conditions VinMin=2.1V, VinMax=2.9V, Vinnom=2.5V, Vout 6V, Iout=0.12A, is it ok to use that design on a PCB with Iout 0.2A or 0.32A?

  • 0 in reply to Andradige Silva
    TI__Expert 3320 points

    Hi Andradige,

    I will still suggest to look for alternative device instead of using 0.12A design. As 0.12 design for your 0.2/0.32 has a high probability to hit current limit. 

    I have moved this post to product expert group for further assistance on this query.

    Best Regards

    Bhushan

  • 0 in reply to Andradige Silva
    TI__Expert 5180 points

    Hi Andradige,

    Yes, since for Vout=6V, Iout=0.32A, VinMin=2.1V, input average current is 915mA. So considering of inductor ripple, it truly has a high probability to hit peak current limit. 

    How about TPS61086, TPS61093 or TPS61251? Their current limit will be a little higher and suitable for 1-3A application. Please watch out the inductor current ripple to avoid hit peak current limit. 

    Best Regards,

    Eric Yue

  • 0
    Prodigy 30 points

    Thank you to both of you.  Now I have a better understanding of this issue.