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TPS43061: Does it work with Vin=Vout?

Part Number: TPS43061
Other Parts Discussed in Thread: TPS40210, LM3478, LM5155, LM5156, LM5122

We need a boost or buck-boost for Vin=9V or 12V and Vout=12V. The input voltage comes from USB-C port with PD support.

I expect TPS43061 to work as a boost at 9V input and to work in bypass mode for 12V. To my surprise, however, in Webench Designer, this is impossible if Vin set to 9 to 12V and Vout set to 12V. This is confusing since if the chip cannot handle a Vin very close to Vout, what is the good to provide a bypass mode?

I also played with a few other chips in Webench Designer. LM3478/3488/3481, LM5156 and TPS40210/40211 do support Vin=Vout, but LM5155 does not.

My question:

1. Does TPS43061 support Vin slightly lower than or equal to Vout (from light load to around 2.5A output)?

2. What is the criteria behind the boost converter or controller that Vin slightly lower than or equal to Vout could be supported?

  • Hi,

    Thank you for reaching out and considering our products in your application. 

    The Webench is intended to support the boost operation so the Vin= or > Vout is not a supported case in Webench. Actually all devices that you mentions can be use d for Vin=Vout or Vin>Vout.  When Vin>Vout, the boost will stop switching, and the rectifier diode will pass the input to the output.  

    If you need bypass operation when Vin>Vout, you may consider the LM5122 or the LM5123, which have a special mode called "bypass", namely the high side FET will be on to pass the input voltage with minimal conduction losses. The LM5122 is a released product, and the LM5123 is our new device currently in sampling under APL.  Both support such bypass operation. 

    Best Regards,

    Youhao Xi, Applications Engineering

  • Thank you for your confirmation.

  • Hi Matian,

    Thank you for confirming and clicking "resolve" button.  Please feel free to contact us if we can be of further assistance.