2.4.3 Simulations

The target impedance of the DDR VDDIO is calculated as 240 mΩ, based on the values (see Power Supply):

  • VSUPPLY = 1.5 V
  • Itrans = 250 mA

  • Ripple = 5%

The impedance profile of the DDR VDDIO plane over frequency range is shown in the following figures. The impedance improves with the decoupling capacitors provided. The target impedance of 0.3 Ω has been achieved till 500 MHz.

Figure 2-15. Impedance Profile of VDDIO0 Plane Over Frequency Range
Figure 2-16. Impedance Profile of VDDIO5 Plane Over Frequency Range