Simulations

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

• V_SUPPLY = 1.5 V
• I_trans = 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 1. Impedance Profile of VDDIO0 Plane Over Frequency Range

Figure 2. Impedance Profile of VDDIO5 Plane Over Frequency Range