calc.engineer / PCB & Electronics / Power Supply Decoupling

Power Supply Decoupling v1.0.0

Select bypass and bulk decoupling capacitors for IC power supply pins. Computes the target PDN (Power Distribution Network) impedance from supply current, voltage, and allowable ripple using Z_target = V_ripple / I_total. Recommends a ceramic bypass capacitor (high-frequency decoupling, placed closest to IC pins) and a bulk capacitor (low-frequency decoupling, near the regulator). Calculates the ceramic cap's self-resonant frequency assuming typical lead inductance, and checks whether ESR-induced ripple stays within limits. Essential for digital, analog, and mixed-signal PCB design. Chain with lc_resonance to verify the decoupling capacitor's resonant behavior, or with trace_width to size the power trace.

← from ohms_law.supply_current_mafeeds lc_resonance →
IC supply current draw in milliamps (mA). Use the maximum or typical from the datasheet.
Supply voltage in volts (V). Common values: 1.8, 2.5, 3.3, 5.0, 12.0.
Primary switching or clock frequency of the IC in MHz. Determines the target impedance frequency range.
Maximum allowable supply ripple in millivolts (mV). Typical: 50 mV for digital, 10 mV for analog/RF.
Number of identical ICs sharing this supply rail. Scales the total current demand.
Equivalent series resistance (ESR) of the ceramic bypass capacitor in milliohms. Typical MLCC: 5-20 mohm.
Fill in the inputs and Compute to see the structured result.

From an agent (MCP) or the API

curl -X POST https://calc.engineer/api/power_supply_decoupling \
  -H "Content-Type: application/json" \
  -d '{"supply_current_ma": …, "supply_voltage_v": …, "switching_freq_mhz": …}'

MCP: connect to https://calc.engineer/mcp and call power_supply_decoupling.

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