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ADC08B200: Choke Coil

Danilo A.
Mastermind 26690 points
Part Number: ADC08B200
Other Parts Discussed in Thread: LM8272

Hi Team,

We're received an inquiry from a customer about the value of the choke coil between VD and VDR of ADC08B200. At page 8 of SNAA125 document in the link below, the value is 2.5 turn ferrite. Can you please suggest a specific value for the choke coil. 

https://www.ti.com/lit/an/snaa125/snaa125.pdf?#page=8 

Regards,

Danilo

  • 0
    TI__Genius 12780 points

    Hi Danilo,

    We typically use a ferrite bead (inductor/choke) to attenuate high frequency noise between power rails. We typically want to avoid having a large inductor, and these ferrite beads have proven to be effective in isolating power rails.

    Here is an example component.

     

    Best Regards,

    Dan 

  • 0 in reply to dBrock
    Prodigy 30 points

    Dear Team,
    I'm an Electronic Engineer student from University of Naples " Federico II " ( Italy ) and I'm working on my degreement project. I'm using ADC08B200 in a configuration that is suggested by the datasheet ( page 32 ), but in the image there's no value and no model of choke inductor that is present on the schematic. This inductor is connected to power supply and it has to clean power supply from spikes. I'd like to know the specific value and model of this inductor. Moreover, there's a capacitor value i'd like to check: it's the one connected to voltage supply, in the first half of operational amplifier LM8272. Should it be 10mF? Sounds suspicious. I am attaching an image for let you know of the configuration i'm talking about.
    Thanks for your patience.
    Lorenzo Abbate 

  • 0 in reply to Lorenzo Abbate
    TI__Genius 12780 points

    Hi Lorenzo,

    We are using the Murata inductor/ferrite bead BLM18AG601SN1D.

    https://www.murata.com/en-us/products/productdetail?partno=BLM18AG601SN1%23

    This, along with the decoupling caps, should provide sufficient noise filtering. You are welcome to use a larger inductor value, but I don't think this is necessary.

    In regard to the capacitor, this should be 10 nano farad (nF).

    Best Regards,

    Dan

  • 0 in reply to dBrock
    Prodigy 30 points

    Dear Dan,
    I've been looking for a 10nF SMD electrolytic capacitor but I found no result. 
    Would you be so kind to suggest me a model ? Should it must be a through hole component? I'm trying to use as much as possibile SMD components on my PCB, so I thought I could replace this 10nF capacitor, in case of only through hole component, with two capacitor in a parallel configuration: a 0.1 uF ceramic one and a 10uF electrolytic one. Could it be a solution ? 
    Thanks for your patience.
    Best regards,
    Lorenzo 

  • 0 in reply to Lorenzo Abbate
    TI__Genius 12780 points

    Hi Lorenzo,

    I think this value is actually referred to as 10000 pF. Here is an SMD part I found.

    Yes, you could also place some capacitors in series/parallel to get the value you need.

    Best Regards,

    Dan