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Key Functions
PIStream can support your PCB design controlling PI (Power Integrity) problem by eliminating input impedance and target impedance. PI problem is occurred by IR drop (Voltage drop) relevant to IC power consumption in PDN (Power Distribution Network). The following three key features are able to support your PI design.
1. Input Impedance Analysis
PIStream calculates input impedance and helps you meet target impedance by adding de-caps, changing capacitor location and changing power plane thickness and shape.
This analysis shows Z11 effect from aggressor IC and allows you to consider optimal capacitor position with try-and-error to keep input impedance below target impedance.
The following figure shows input impedance (Z11) structure.
(1) Countermeasure by Input Impedance Analysis
Case 1: Target impedance achieved by adding capacitors around target IC.
Adding capacitors around red area near by target IC makes input impedance being below target impedance. You will be able to optimize capacitor location from this analysis.
Case 2: Target impedance achieved by changing thickness between power and GND plane.
This case shows that thinner of the insulator thickness makes input impedance being below target impedance.
(2) Auto Capacitor Placement
This function selects optimum capacitors for resonance frequency and places them near IC power pins automatically. The following figure shows the effect before and after running auto capacitor placement function.
Input impedance is above target impedance before running this function, however after running, 8 capacitors are added around IC power pins and color gradaction turns to bule.
(3) Target Impedance Setting for Input Impedance Analysis
This GUI allows you to enter allowable maximum impedance value which is supplied by IC venders. You can also import CSV file into this GUI.
This setting will appire a red line as reference impedance value in the input impedance analysis result.
2. Transfer Impedance Analysis
PIStream calculates transfer impedance to avoid noise transition to other ICs and internal RF interference.
The following figures are the result of transfer impedance analysis.
This functions allows you to consider noise distribution caused by power source (aggressor) IC. Hot area means high transfer impedance area, and it indicates huge voltage drop (IR drop) is occurred when aggressor IC consumes current. To avoid this voltage drop, you can put a capacitor on the red area. By doing this, red area turns to blue and you will be able to confirm if transfer impedance is reduced and suppressed noise distribution.
This analysis shows Z21 (Transfer Impedance) effect using color gradation map.
Transfer impedance is calculated by power noise emission from power source IC.
3. DC Analysis (IR Drop)
PIStream also calculates IR Drop and display color gradation as well as IR Drop value for each IC.
