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ADP5050 Discontinuous Transient Voltage Drop

Product Number: ADP5050

Hello,

I am working on an ADP5050 design and have noticed in simulation the voltage drop due to a 0.5A step load is quite bad.  I'm in need of thoughts/comments on how/if I can improve this.  I've run the design for a 1.0V output supply rail in LTSpice which is working well, but I'm struggling to reduce the stop load output undershoot when using a load of 0.5A.  Because this is a 1.0V rail a noticeable voltage drop is a problem.  I'm seeing a ~300mV drop when in discontinuous mode which is a problem for me. 

Screenshot of my LTSpice sim.

Blue = inductor current

Green = output voltage

Teal = step load enable

Red = stepload "load" current

In continuous conduction mode this is much better, but I'm unsure how to improve this as I have to support a lighter load when powering up an FPGA with no bitstream.  Does anyone have any advice?  The green line "V(out)" shows the large dip due to a 0.5A step load.

Here is another screenshot showing the output voltage droop due to the step load.

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  • Hi,

    Is efficiency a tight requirement for you? If not, you might want to consider forced PWM on your design by tying your Sync_mode pin high (e.g. to Vin). That will significantly improve your output voltage ripple. 

    Using the same circuit except using Forced PWM, I got this result:

    Blue - Vout

    Green - Inductor Current

    Red - SW node

    Teal - Output Load

    You can also modify your compensation value to further improve your design. LTSpice have the new FRA tool to help you shape your loop response.

    Good luck!

    Regards,

    Audison

Reply
  • Hi,

    Is efficiency a tight requirement for you? If not, you might want to consider forced PWM on your design by tying your Sync_mode pin high (e.g. to Vin). That will significantly improve your output voltage ripple. 

    Using the same circuit except using Forced PWM, I got this result:

    Blue - Vout

    Green - Inductor Current

    Red - SW node

    Teal - Output Load

    You can also modify your compensation value to further improve your design. LTSpice have the new FRA tool to help you shape your loop response.

    Good luck!

    Regards,

    Audison

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