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LMR36510: LMR36510

ANURAJ NK1
Prodigy 170 points
Part Number: LMR36510
Other Parts Discussed in Thread: LV2862

Hi, 

I am looking for a DC Converter design which consume less than 1mA current in quiescent mode. The current design is taking 3mA. Can you suggest modifications to the existing circuit to get lower current.

I measured the current at Vin pin. R61 was DNP during the testing.

Below is the current design.

C23, R37  :   DNP

C24 & C29 : 4.7uF/50V

R59,R61 : Is used for debug purpose. Will removed from final design.

Nominal Input voltage : 24V

Max output current : 1mA

Regards

Anuraj NK

  • 0
    TI__Mastermind 28020 points

    Hi Anuraj,

    I am unable to see the schematic here in your post.

    Can you send it to me directly at jarrigo@ti.com.  

    Thanks, Jason

  • 0 in reply to J Arrigo
    TI__Mastermind 28020 points

    Hi Anuraj,

    Since we have taken this post offline, I will close this post. Feel free to respond back if more help is needed.

    Thanks, Jason

  • 0 in reply to J Arrigo
    Prodigy 170 points

    Hi,

    During the DC Converter testing, I am hearing humming sound from the Circuit. I hope  it is from Inductor during the switching. Do you expect this behavior on this design? Can you suggest me how to stop this sound?

    Regards

    Anuraj NK

  • 0 in reply to ANURAJ NK1
    TI__Mastermind 28020 points

    Hi Anuraj,

    Does the humming only occur at light load? If the load increases does the humming go away?

    This device operates in PFM mode at light load. In PFM mode the device turns on in bursts at a lower frequency. This frequency may be audible.

    You could monitor the SW pin to observe the switching frequency.

    Regards, Jason

  • 0 in reply to J Arrigo
    Prodigy 170 points

    DC DC Convert will consume only 5mA or less when the board is functional. I didn't test it with higher load since my load requirement is only 5mA.

    Will this humming sound cause EMI Issue ? Radiated or conducted emission.

    Is there any alternate part with same foot print  / suggestions to remove this humming sound.

  • 0 in reply to ANURAJ NK1
    TI__Mastermind 28020 points

    Hi Anuraj,

    If you want to verify at higher load if the noise goes away, you could place a resistor (100 to 500Ω) across an output cap to draw a larger load. 

    You can also measure the SW node to measure the frequency of the bursts. That would be helpful.

    The humming will not cause EMI issues. However, the lower frequency switching during PFM mode may cause noise at unwanted frequencies.

    If the humming is caused by PFM mode during light load, the best option would be to select a device with the option to disable PFM (this will mean worse light load efficency). You may also decide to use a lower current rated device which would be better suited for a 5mA application.

    Regards, Jason

  • 0 in reply to J Arrigo
    Prodigy 170 points

    Thanks. I am preparing the setup to measure the SW Node frequency. Mean time can you suggest some alternate parts which suits for 5mA current

  • 0 in reply to ANURAJ NK1
    Prodigy 170 points

    Hi,

    Can I use the part LV2862XLVDDCR. It works in ECO mode at low current. Do you see any possibility of humming sound or EMI Related issue with this part when the output is loaded with 5ma or less current. Please confirm.

    I am going to use the below schematics for my Design with couple of bulk caps at the input & Output side. Hope this will works fine.

    Regards

    Anuraj NK

  • 0 in reply to ANURAJ NK1
    TI__Mastermind 28020 points

    Hi Anuraj,

    I think you first need to measure the SW node and increase the current to verify that ECO mode operation is the causing the noise.

    Since the LV2862 device also has ECO mode, it may also produce this noise.

    With so low of current, is there a reason that you are not using a linear regulator?

    Have you tried entering your parameters into Webench? 

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

  • 0 in reply to J Arrigo
    Prodigy 170 points

    Hi,

    I could have used an LDO. I tried finding an LDO part. I couldn't locate on. I got one part which is Non-ROHS complaint TPS7B8150QKVURQ1.

    I cannot use Non-ROHS part. Can suggest an LDO part with lower price and lower Junction-to-ambient thermal resistance. 

    Below is my Spec:

    Vin (Max) = 30V

    Vout = 5V

    Iout (Max) = 20mA

    Ambient Temp= 60Deg

    Regards

    Anuraj NK

  • 0 in reply to ANURAJ NK1
    TI__Mastermind 28020 points

    Hi Anuraj,

    TI has many LDOs that would be perfect for your application. I have filtered a list at the link below.

    Most all devices are RoHS compliant. Look at the Packaging Information page at the end of the datasheet for the info on each orderable part number. 

    Regards, Jason