• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 64 subscribers
  • Views 545 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TLV1117LV: Do I need Ferrite bead for TLV1117LV33

daniel lin
Prodigy 220 points
Part Number: TLV1117LV

I know DCDC is required to add ferrite bead.

Based on the common practice in using TI TLV1117LV33, should I have to add ferrite bead to minimize the EM or just 10uF X7R ceramic capacitor is sufficient?

I used USB type-A to supply 5V to TLV1117LV3.3, and used the converted 3.3V to drive ESP32 WiFi/BLE module.This ESP32 WiFi/BLE module is covered by metal shielded with FCC approved. This my simple WiFi/BLE gateway circuit.

The 110V->5V power supply will be sourced from third party, which is also UL approved.

  • 0
    Prodigy 220 points

    Sorry for the typo: the output cap 10uF should be X5R, not X7R.

  • 0 in reply to daniel lin
    TI__Mastermind 18466 points

    Hey Daniel, 

    If you need to add a ferrite bead to the output of the LDO, the effective output impedance has to be above 0.5uF as noted in the datasheet to maintain stability. 

    It serves to note that a ferrite bead only filters out high frequency noise - so whether or not you need one is based on your application (WiFi module and DC/DC converter) and PCB layout. 

    Best,

    Juliette

  • 0 in reply to Juliette
    Prodigy 220 points

    What is the criteria to choose the right ferrite bead at the input of LDO? Higher than 100MHz noise at how many mv? Thanks.

  • 0 in reply to daniel lin
    TI__Mastermind 18466 points

    Hey Daniel, 

    Choosing a ferrite bead is going to depend on the exact frequency you need to attenuate (they do not work like low-pass filters) and the specifications provided by the manufacturer's data sheet - specifically the impedance v. load curve. Depending on the load of your device, you need to choose a ferrite bead that will not saturate at that load.

    Don't forget to take the voltage drop across the ferrite bead into consideration, along with its heat dissipation.

    Best,

    Juliette