Vout = Vin × (R2 / (R1 + R2)) - leave one field empty to solve
Nearest standard resistor value to a calculated target - works for any E-series part
Best standard resistor pairs for a target Vout = Vin × R2 / (R1 + R2)
R = (Vs - Vf) / If, rounded up to E24
Time for a capacitor charging toward Vs to cross Vth: t = -RC × ln(1 - Vth/Vs)
Copper wire resistance, one-way voltage drop, and rule-of-thumb ampacity (~4 A/mm² bundled, ~10 A/mm² in free air)
Rmin from VOL sink current (0.4 V spec), Rmax from rise time: tr = 0.8473 × R × Cb. Standard mode 1000 ns, fast mode 300 ns
C1 = C2 = 2 × (CL - Cstray). CL from the crystal datasheet; stray is typically 3-5 pF of pin + trace capacitance
LSB = Vref / 2^N, ideal SNR = 6.02N + 1.76 dB (full-scale sine)
R = R25 × exp(β × (1/T - 1/298.15)) - fill T or R, leave the other empty to solve
P = I² × Rds(on), Tj = Ta + (P × θja)
Psw = Qg × Vgs × fsw, Pcond = I² × Rds(on)
GBP = Gain × Bandwidth - leave one field empty to solve
fc = 1 / (2πRC) - leave one field empty to solve
Unity-gain, equal-R design: C1 = 4Q² × C2, R1 = R2 = 1/(4πQ × fc × C2). Q = 0.707 for Butterworth
Sine-wave conversions at a given impedance: P = Vrms²/Z, Vpp = 2√2 × Vrms. Enter one value, leave the rest empty
Estimates runtime based on capacity, sleep power, and TX events
L = (Vout × (Vin - Vout)) / (Vin × fsw × ΔI)
D = 1 - Vin/Vout, L = (Vin × D) / (fsw × ΔIL). Note the inductor carries the input current: IL = Iout / (1 - D)
ΔVout = ΔIL × ESR + ΔIL / (8 × fsw × C). ΔIL from the inductor sizing calc above
P = (Vin - Vout) × I, Tj = Ta + P × θja - the 'do I need a heatsink' check
P = I²rms × ESR, estimates temperature rise
Measure the switch-node ring frequency (f1), add a test cap and measure again (f2). R = √(Lpar/Cpar), Csnub ≈ 3 × Cpar
Minimum width for a current and allowed temperature rise: I = k × ΔT^0.44 × A^0.725. Resistance at 20 °C for the computed width
Calculates characteristic impedance for microstrip or stripline
Edge-coupled pair (IPC-2141 approximation) - for USB, RS-485, Ethernet etc.
Barrel treated as an internal IPC-2221 conductor. L ≈ 0.2 × h × (ln(4h/d) + 1) nH
Safety spacing per IEC 60664-1 (clearance from the rated impulse voltage, creepage from working voltage, pollution degree and material group) alongside the IPC-2221B functional spacing table. Tables are as published; the standard and your product standard govern.
Clearance (shortest path through air) is dimensioned against transients. The rated impulse voltage comes from the supply's nominal line-to-neutral voltage and the overvoltage category (Table F.1), or from the peak working voltage plus 1200 V for circuits that see no mains transients. Table F.2 converts it to a distance for the pollution degree. The distance is also checked against the steady-state peak (Table F.7a) and the larger governs. Above 2000 m the distance is multiplied by the Table A.2 factor. Reinforced insulation uses the next impulse value in the preferred series and 160 % of the steady-state peak.
Creepage (shortest path along the insulating surface) is dimensioned against tracking under long-term working voltage. Table F.4 gives it from the RMS or DC working voltage, the pollution degree and the material group; the printed wiring columns apply to conductors on a printed board under pollution degrees 1 and 2 up to 1000 V. Reinforced insulation doubles the basic value. Creepage may never be less than the clearance. The table is entered at the next higher voltage row; the standard permits linear interpolation between rows.
IPC-2221B Table 6-1 is a design guideline for proper functional operation, not a safety standard. It is entered with peak or DC voltage, gives spacing for internal and external layers with and without coating, and adds a per-volt increment above 500 V. IPC-9592B (computer and telecom power conversion) is slightly more conservative.
Pollution degree. 1: no pollution or dry non-conductive pollution only (sealed, potted, or conformally coated to exclude condensation). 2: non-conductive pollution with occasional condensation (offices, homes, equipment enclosures). 3: conductive pollution, or dry pollution that becomes conductive through expected condensation (industrial, unheated rooms). 4: persistent conductivity from dust, rain or snow; outside the scope of these tables.
Overvoltage category. I: circuits with transient limiting (transformer-fed 24 V controls). II: equipment plugged into the fixed installation (appliances, portable tools). III: fixed installation and distribution (panels, hardwired industrial machinery). IV: origin of the installation (meters, primary overcurrent protection).
Material group by comparative tracking index: I ≥ 600, II 400 to 599, IIIa 175 to 399, IIIb 100 to 174 or unspecified. Most FR-4 is IIIa; isolator IC packages are often group I, which is why the PCB rather than the part sets the creepage.
Product standards refine these values: IEC 62368-1 (audio, video, IT and communications) Tables 10 and 17, IEC 61800-5-1 (drives) Tables 9 and 10, IEC 62109-1 (solar) Tables 13 and 14. Their clearances for a given impulse are somewhat larger (for example 1.8 mm rather than 1.5 mm at 2.5 kV in IEC 62368-1). Conformal coating per IEC 60664-3 can reduce the pollution degree under the coating. Frequencies above 30 kHz are covered by IEC 60664-4.