AM67: Function of LC Low-Pass Filter (EMIFIL) in AM67 design

Part Number: AM67

Tool/software:

Hi Sirs

I see there are a lot of LC Low-Pass Filter (EMIFIL) in AM67 reference design (PROC170E3(002)_SCH), including 10uF and 1uF.

However, we have two questions about this, please help to answer it.

1. Why short pin 1 and pin3?  

    Reference design shows all LC Low-Pass Filter (EMIFIL) are short pin 1 and pin3, but from Murata's website, pin 1 and pin 3 should be in/out function.

    Could you explain why these pin short together?

2. Reviewing the layout, you can see these filters are line up together (yellow in the picture below), and not stay near the pin as normal layout guideline.

   Could you let me know what's the purpose of this special pattern?

We are planning to use AM67 but limitation of layout space, so we want to know the function of these LC Low-Pass Filter (EMIFIL), so we can decide how to reduce them or replace them, thank you.

  • The 3-terminal capacitors can be used in different configurations.  Connecting pins 1 and 3 to power supply uses the capacitor for a standard decoupling capacitor.  The benefit of the 3-terminal capacitor over standard 2-termincal capacitor is a lower package inductance which leads to better decoupling performance.  Its up to each customer to use the 3-terminal decoupling capacitor or not - but TI does recommend.