Name: PDC Capacitors FM21N101J251PXG 0805 C0G 250V 100PF
Brand: Walsin
SKU: FM21N101J251PXG
Availability: InStock

Question 1

What is the difference between C0G, X7R, X5R, and Y5V MLCCs?

Accepted Answer

C0G (NP0) is a Class 1 dielectric with ±30ppm/°C stability, zero DC bias effect, and DF under 0.1% — use it for resonant circuits, timing, and precision filters. X7R is a Class 2 dielectric with ±15% tolerance over -55°C to +125°C and moderate DC bias roll-off, ideal for decoupling, bypass, and general-purpose filtering. X5R offers higher capacitance density than X7R but only spans -55°C to +85°C. Y5V delivers the highest density but swings +22% to -82% across -30°C to +85°C and can lose 70-90% of its rated capacitance at operating voltage.

Question 2

Why does my MLCC measure much lower capacitance than the marked value?

Accepted Answer

Class 2 dielectrics (X7R, X5R, Y5V) lose capacitance under DC bias voltage. At rated voltage, an X7R capacitor may retain only 50-70% of its nominal capacitance, while Y5V can drop to 10-30%. Always consult the manufacturer DC bias curve and derate accordingly. C0G/NP0 has zero DC bias effect.

Question 3

Do MLCC capacitors age, and can the aging be reversed?

Accepted Answer

Class 2 dielectrics experience logarithmic capacitance aging, with X7R losing about 1% per decade-hour and Y5V losing about 5%. Aging is reversible — heating the capacitor above its Curie temperature (typically during soldering) resets the curve. Class 1 C0G/NP0 has negligible aging.

Question 4

What causes MLCCs to crack, and how can I prevent it?

Accepted Answer

MLCC cracking is the most common field failure and is almost always mechanical in origin — PCB flexure during depaneling, thermal shock from improper soldering profiles, or physical stress from board handling. Cracks start at terminations and propagate inward at 45°. Prevent by placing MLCCs parallel to board flexure, away from edges and mounting holes, and following manufacturer reflow profiles.

Question 5

How much voltage derating should I apply when selecting a component?

Accepted Answer

Apply at least 50% voltage derating for general reliability. In filter circuits, the voltage rating should be at minimum 1.42× the AC RMS voltage. For DC applications, add 20-50% margin above your maximum operating rail. Higher derating significantly extends service life at elevated temperatures.

Question 6

Is lower ESR always better?

Accepted Answer

Not always. Low ESR improves ripple current handling and reduces self-heating for power supply filtering. However, excessively low ESR can destabilize switching regulator feedback loops and cause oscillations. Above the self-resonant frequency, the component behaves inductively regardless of ESR. Match the component to the application.

Question 7

What are X and Y safety capacitors, and where are they required?

Accepted Answer

X capacitors bridge line-to-neutral for differential-mode EMI (X1/X2/X3 classes). Y capacitors connect line-to-ground for common-mode noise (Y1/Y2/Y3/Y4). Per GJB151, Y capacitor values must not exceed 0.1µF to limit leakage current to safe levels.

Question 8

What is silver ion migration, and how do I protect against it?

Accepted Answer

In silver-electrode components operating in humid environments, water electrolyzes under DC bias. Silver ions migrate from the anode, depositing conductive dendrites that short electrodes. This is severe in monolithic ceramic capacitors. The most effective countermeasure is conformal coating after PCB assembly.

Question 9

Where should I place decoupling capacitors on a PCB?

Accepted Answer

Place decoupling capacitors as close as physically possible to the IC power and ground pins — every millimeter of trace adds parasitic inductance. A 0.1µF MLCC in parallel with a 10µF bulk capacitor covers a wide frequency range. Use the shortest via path to power and ground planes.

Question 10

How can I test whether a capacitor is good using a multimeter?

Accepted Answer

For capacitors ≥0.01µF, use R×10k range. The needle should swing right then return toward infinity. No movement = open-circuit. Stays at zero = shorted. Returns to under 500kΩ = excessive leakage. For electrolytics, forward leakage should be at least several hundred kΩ. Always discharge before testing.

Question 11

How do I get a datasheet and RFQ for a specific part number?

Accepted Answer

Click Request a Quote on the product page, fill in your part numbers and target quantities, and submit. Our team responds within 24 hours with datasheet links, competitive pricing, and current lead time information. Volume discounts available for production quantities. You can also email info@movthing.com directly.

Question 12

How do I choose the right package size for my design?

Accepted Answer

Larger packages handle higher voltage and capacitance but have higher ESL and are more vulnerable to mechanical cracking. 0201-0402 suit space-constrained mobile. 0603-0805 for general-purpose. 1206-1210 for power applications. 1812-2220 for high-voltage requirements but require careful placement away from flexure zones.

RoHS	Yes
Applications	commercial
Size	0805
Capacitance	100PF
Temperature	C0G
Voltage	250V
Tolerance	±5%
Description	0805 C0G 250V 100PF ±5%

RoHS	Yes
Applications	commercial
Size	0805
Capacitance	100PF
Temperature	C0G
Voltage	250V
Tolerance	±5%
Description	0805 C0G 250V 100PF ±5%

PDC Capacitors FM21N101J251PXG 0805 C0G 250V 100PF

Specifications

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