Microsemi IGLOO2 - Figure 33 Impedance Profile of Serdes_X_Vdd Plane over Frequency Range; Figure 34 Impedance Profile of Serdes_X_Vddaio Plane over Frequency Range

Layout Guidelines for SmartFusion2- and IGLOO2-Based Board Design
AC393 Application Note Revision 14.0 45
Figure 33 • Impedance Profile of SERDES_x_VDD Plane Over Frequency Range
3.3.3.2 SerDes I/O Power (SERDES_x_VDDAIO)
The target impedance of the SERDES_x_VDDAIO pin is calculated as 240 mΩ, based on the following
values (see Power Supply, page 38):
•V
SUPPLY
= 1.2V
•I
trans
= 250mA
• Ripple = 5%
The following figure shows the impedance of the plane (SERDES_x_VDDAIO) improved by the
decoupling capacitors. The impedance of the plane is kept under 0.2 Ω till 100 MHz.
Figure 34 • Impedance Profile of SERDES_x_VDDAIO Plane Over Frequency Range
Z Amplitude (Ω)
Frequency (GHz)
SERDES_x_VDD with Decoupling Capacitors
SERDES_x_VDD without Decoupling Capacitors
1e3
100
10
1
0.1
1e-4 2e-4 1e-3 2e-3 0.01 0.02 0.1 0.2 0.3 1 2 3
Z Amplitude (Ω)
Frequency (GHz)
Impedance of SERDES_x_VDDAIO with Decoupling Capacitors
Impedance of SERDES_x_VDDAIO without Decoupling Capacitors
1e3
100
10
1
0.1
0.01
1e-4 2e-4 1e-3 2e-3 0.01 0.02 0.1 0.2 0.3 1 2 3