PDN Impedance

Decoupling network impedance vs frequency against the target impedance: anti-resonance peaks, compliant bandwidth, and each capacitor group’s self-resonance

Target Impedance

Rail Voltage(V)

Allowed Ripple (± of V)(r)

Transient Current Step (often 50% of Iₘₐₓ)(ΔI)

Analysis Band

Band Start(fₘᵢₙ)

kHz

Band End(fₘₐₓ)

MHz

Voltage Regulator

VRM Output Model (R + jωL)

Output Resistance(Rᵥᵣₘ)

mΩ

Output Inductance (above loop bandwidth)(Lᵥᵣₘ)

Capacitor Group 1

Part — ESR 15 mΩ, ESL 2.5 nH (typical — use your part’s datasheet)

Quantity (0 = off)(N)

pcs

Mounting Inductance (pads + vias)(Lₘ)

DC-Bias / Aging Capacitance Loss(d)

Capacitor Group 2

Part — ESR 5 mΩ, ESL 0.65 nH (typical — use your part’s datasheet)

Quantity (0 = off)(N)

pcs

Mounting Inductance (pads + vias)(Lₘ)

DC-Bias / Aging Capacitance Loss(d)

Capacitor Group 3

Part — ESR 15 mΩ, ESL 0.4 nH (typical — use your part’s datasheet)

Quantity (0 = off)(N)

pcs

Mounting Inductance (pads + vias)(Lₘ)

DC-Bias / Aging Capacitance Loss(d)

Capacitor Group 4

Part — ESR 30 mΩ, ESL 0.4 nH (typical — use your part’s datasheet)

Quantity (0 = off)(N)

pcs

Mounting Inductance (pads + vias)(Lₘ)

DC-Bias / Aging Capacitance Loss(d)

Plane Pair

Power / Ground Plane Capacitance

Plane Length(ℓ)

Plane Width(w)

Dielectric Thickness(h)

µm

Dielectric Constant(εr)

Loss Tangent(tanδ)

Plane ESL (0 = ideal capacitance)(Lₚ)

Load Path

Spreading + Package L (0 = board only)(Lₛ)

Design looks good

Meets Target

0.88

Worst |Z| / Zₜ (×)?

100

Worst-Case At (MHz)?

100

Compliant Up To (MHz)?

Results

Target Impedance(Zₜ)?

20.0mΩ

Worst |Z| in Band?

17.6mΩ

Worst-Case Frequency?

100MHz

Worst |Z| / Target?

0.88×

Compliant Up To?

100MHz

Band Above Target?

0.0%

Anti-Resonance Peaks?

Highest Anti-Resonance?

4.02MHz

|Z| at Highest Anti-Resonance?

8.91mΩ

Total Capacitance(ΣC)?

698µF

Mounted L, All Caps(L∥)?

27.9pH

Inductive Limit?

114MHz

|Z| at 100 kHz

7.22mΩ

|Z| at 1 MHz

3.63mΩ

|Z| at 10 MHz

4.79mΩ

|Z| at 100 MHz

17.6mΩ

Plane Capacitance(Cₚ)?

3.05nF

Impedance vs Frequency

|Z| at load
Target Zₜ
VRM
Group 1
Group 2
Group 3
Group 4
Plane

Worst |Z| = 17.6 mΩ at 100 MHzZₜ = 20.0 mΩPeaks: 3

Anti-Resonance Detail

#	Frequency	\|Z\|	vs Zₜ	Q	Inductive ↔ capacitive
1	429 kHz	7.91 mΩ	0.40×	0.6	Group 1 ↔ Group 2
2	4.02 MHz	8.91 mΩ	0.45×	2.9	Group 2 ↔ Group 3
3	12.8 MHz	8.50 mΩ	0.43×	3.3	Group 3 ↔ Group 4

Network Branches

Branch	Part	N	C_eff each	R / N	L / N	f₀ (SRF)
VRM	R + jωL	—	—	1.00 mΩ	20.0 nH	—
Group 1	Polymer 330 µF	2	330 µF	7.50 mΩ	1.50 nH	160 kHz
Group 2	0805 10 µF	4	8.00 µF	1.25 mΩ	263 pH	1.74 MHz
Group 3	0402 1 µF	6	750 nF	2.50 mΩ	117 pH	6.95 MHz
Group 4	0402 100 nF	16	90.0 nF	1.87 mΩ	43.8 pH	20.1 MHz
Plane	tanδ 0.02	—	3.05 nF	—	—	f₁₀ 723 MHz

L includes ESL and mounting inductance. Peak partners are the branches with the most inductive and most capacitive susceptance at the peak.

Created by Catlynn Nguyen & Jie Chai · 2026