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TIVA TM4C123G and by pass coupling capacitor

C
Expert 2065 points

The design guide mention one by pass decoupling capacitor should be placed on each VDD bin typicaly. However if you look at some reference design such as DK TM4C123G you can see there are less decoupling capacitor than VDD pin. 

What to do then ?

Can you explain for example, the logic in this schematic: : 4 VDD pin, but 6 capacitor which I suppose are grouped by 2, but in this case where the last one 1.0uf is going ?

  • 0
    TI__Guru**** 244380 points
    Hello Chris

    1.0uF is a bulk capacitor while other 5 are for 4 VDD+ 1VDDA pin.

    Regards
    Amit
  • 0 in reply to Amit Ashara
    Expert 2065 points

    Why the value of decoupling capacitors are not all same ?

  • 0 in reply to C
    Expert 2065 points

    Hello, 

    I need some help to know which capacitor I have to put on those pins (they are all VDD and from my understanding and based on the design guide, there shoudl have 0.1uF + 1 bulk capacitor which I don't know the value.

    However on page 23 of the hardware design guide there are some screenshot and you can see the cap are not equally spreaded on the layout ( I am on the 144 pin LQFP)

    Can you please specify how many capacitor I need and with each value on those pins below:

    137
    124 
    113
    101
    94
    78
    66
    56
    43
    29
    24
    7

    Thank you for your help in advance