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LM61460: Bias input shorted to ground.

May
Genius 9880 points
Part Number: LM61460

Hi Team, 

Good day, our customer want to know the reason why in webench design the bias input is shorted to ground in a 1.55V/2A output (input 9-32V)

In the datasheet description of BIAS pin it mention that  you can connect this pin to ground when Vout is above 12V.

Thank you and looking forward for your kind response.

Regards,

Maynard

  • 0
    TI__Guru 50120 points

    Hi,

    Thank you for pointing this out. I believe this was incorrectly set in the simulation.

    I'll contact the WEBENCH support team and mention this so that BIAS pin is connected to ground only when VOUT is 12V or higher.

    In your schematic, please have BIAS connected to VOUT.

    Regards,

    Jimmy 

  • 0 in reply to Jimmy Hua
    Intellectual 280 points

    I'm not sure your conclusion is correct , because in the LM61460 DataSheet is stated :

    " The BIAS pin is the input to the internal LDO. This input can be connected to VOUT to provide the lowest possible input supply current. If the BIAS voltage is less than 3.1 V, VIN1 and VIN2 directly powers the internal LDO".

    In my case VOUT = 1.55V < 3.1V and seems in this case it's possibly to connect  BIAS to the ground ( 0V < 3.1V), so Simulation result is correct. Can you comment?

  • 0 in reply to Alex Khramov23
    TI__Guru 50120 points

    Hi Alex,

    I've contacted the systems engineer to get more information on the internal bias circuitry. 

    The BIAS pin can be tied GND for output voltages lower than 3.3V. 

    As you pointed out simulated results look correct.

    Regards,

    Jimmy