Understanding how 350,000 nH becomes 350 uH for SMT inductors

Outline:

• Hook: Units matter—nH vs μH isn’t just nerdy trivia, it’s real design stuff.

• Core conversion: Explain the math behind 350,000 nH to 350 μH. Show the simple rule: 1 μH = 1000 nH.

• Why it matters: How inductance choices shape filters and power converters; the practical consequences of prefixes in datasheets.

• Quick mental math tips: A few easy habits to avoid misreads when reading BOMs or app notes.

• SMT inductors in the real world: beyond the label—tolerance, current rating, DC resistance, and self-resonant frequency.

• How to verify: a note on measuring inductors with LCR meters and what to look for in tests.

• A friendly analogy: thinking in water pipes and reservoirs to visualize the scale shift.

• Takeaway: Keep prefixes straight, and your designs stay in harmony.

350 μH: the simple truth hiding in plain sight

Let me explain a tiny but mighty detail that sneaks into every PCB designer’s laptop bag: unit prefixes. When you see a number like 350,000 nH, your brain should whisper one thing softly but firmly: that’s 350 μH. Why? Because 1 μH equals 1,000 nH. It’s the kind of rule that looks obvious after you’ve done the math once, but can trip you up if you try to read too fast.

So the quick math is this:

• 350,000 nH ÷ 1,000 = 350 μH.

• That’s the same inductance, just written with a different prefix.

If you’ve ever stared at a BOM or a datasheet and found a value written as nH on one line and μH on another, you’ve likely felt that little tug of confusion. It’s not a mystery so much as a formatting shortcut; the electronics world loves prefixes because they keep numbers readable without losing precision.

Why this simple conversion matters in the real world

Inductors are hiding in all sorts of places on a board: the input filter of a buck converter, the output filter of a boost converter, an RF front end, or a simple choke in a power line. The exact inductance value you choose isn’t just a number—it drives impedance at a target frequency, shapes ripple, and interacts with capacitors and switching frequencies.

• In a buck regulator, the inductor value sets the ripple and the transient response. If you misread 350 μH as 350 nH, you’ve effectively swapped a big energy storage device for a tiny one, and the circuit won’t behave as intended.

• In a high-frequency RF path, you might see nanos or micros used depending on the needed reactance at the signal frequency. The wrong prefix invites miscalculation, and with it, mismatched filters or unstable biasing.

• Datasheets use prefixes to keep numbers readable. A 10 μH inductor and a 10,000 nH inductor are the same thing expressed differently. The trick is to stay consistent within a design so you’re comparing apples to apples.

A few quick mental math tips so you don’t sweat the small stuff

• The 1000 rule is king: count the zeros. Every μH is three more zeros than nH. So 1 μH = 1000 nH, 2 μH = 2000 nH, and so on.

• If you’re scanning a BOM and see “nH,” you can mentally shift to μH by dropping three zeros and adding the μH label when it makes more sense for the context.

• When in doubt, write both sides of a conversion on a sticky note near your workstation: “350,000 nH = 350 μH.” It’s a reminder that your numbers are the same, just written differently.

The practical side of SMT inductors

A value like 350 μH on a BOM sounds straightforward, but inductors bring more to the table than just a number. Keep these practical considerations in mind:

• Tolerance: Inductors aren’t perfect. A 350 μH part might be ±5%, ±10%, or even more in some high-volume SMT families, depending on the series and material. That means the actual inductance could swing by tens of microhenries. When your circuit relies on a tight impedance, you factor this into your design margins.

• DC resistance (DCR): The copper coil has resistance. Higher inductance parts often come with higher DCR, which means more voltage drop and more heat at a given current. It’s a balancing act: more inductance but more wasted energy at high currents.

• Saturation current: An inductor has a maximum current it can carry before its inductance starts to drop (saturate). If your regulator has a surge or load step that pushes the current, you’ll want an inductor with a saturation rating comfortably above that peak.

• Self-resonant frequency (SRF): Every inductor resonates with its own parasitics at some frequency. If your circuit runs near that SRF, the inductance can react unpredictably. For a 350 μH part, the SRF is typically well below RF ranges, but it’s worth checking in high-frequency designs.

• Size and footprint: SMT inductors come in a range of sizes. A larger inductance often means a physically larger coil. If you’re stacking parts in a tight layout, you may need to juggle board real estate versus performance.

Verification on the bench: there’s a quick reality check

When you’re noodling with inductors, a little hands-on testing goes a long way. A basic LCR meter or impedance analyzer can confirm the inductance value at your target frequency and temperature.

• Measure at your operating temperature, if you can. Inductors drift with temperature, sometimes noticeably.

• Check the tolerance by measuring a few samples from the same reel. You’ll quickly see how much leeway you’ve got.

• Confirm the DC resistance and, if relevant, the saturation current from the vendor data sheet. It helps prevent nasty surprises in a live circuit.

A friendly analogy to keep the idea clear

Think of inductance as water storage and flow in a pipe system. The inductor is a reservoir that slows down changes in current. A small reservoir (low inductance) lets changes pass quickly—great for fast filters but not ideal when you need to smooth every ripple. A big reservoir (high inductance) smooths more, but it takes longer to fill and it can heat up if you push a lot of current through it. Prefixes are just the labeling that tells you the size of that reservoir. Reading the exact label is like checking the pipe diameter and the tank capacity before you redesign the plumbing.

Putting it all together with a real-world sense of scale

Let’s circle back to the 350,000 nH example. It’s a 350 μH inductor in practical terms. If your design calls for a 350 μH choke in a DC-DC converter’s output, you’re balancing ripple amplitude, response time, and heat dissipation. If you instead misread it as 350 nH, you’d be chasing a totally different creature—one that stores far less energy and responds at a much higher frequency. The result would likely be a circuit that looks fine on paper but behaves badly in hardware.

Common slip-ups worth avoiding

• Mixing prefixes without consistency: If you jot down nH in one place and μH in another without noting the change, you’ll confuse yourself and teammates.

• Ignoring tolerance in critical paths: For a precision filter or a tight regulator loop, that ±5% or more can derail performance.

• Forgetting SRF in high-frequency paths: Even a small misstep in an RF input or a fast switching regulator can push you into an unpredictable region.

• Overlooking temperature drift: In harsh environments or hot boards, inductors aren’t constant. Plan for it in your design margins.

A few related notes you’ll hear in professional discussions

• When you read a vendor’s catalog or an app note, you’ll see inductors described in μH or nH depending on the target market. Designers often convert to the more intuitive unit for a given context, and yes, it’s perfectly normal to keep a quick reference handy.

• If you’re prototyping with a range of inductors, you’ll sometimes label them in a notebook as “350 μH (±5%)” and later cross-check with a measurement. It keeps the debug path clear.

• In assembly and board-level documentation, clarity beats cleverness. A single line that states “Inductor L3: 350 μH, ±5%, 1Ω DCR, 1.2 A rating” saves a lot of guessing later.

A closing thought: why this little unit matters

Numbers are the language of electronics, and prefixes are the grammar. Getting them right isn’t a flashy skill; it’s the sort of practical know-how that keeps projects moving from concept to a steady, reliable performance. The next time you see a stubborn BOM, take a moment to translate the nH into μH, or vice versa. It’s a small act with a big payoff: fewer reworks, clearer communication, and circuits that behave the way you expect.

If you’re curious about more nuances, you’ll find that inductors sit at the intersection of physics and design judgment. They’re not just parts on a list; they’re the quiet workhorses that tame ripple, stabilize rails, and ensure signals travel cleanly through a noisy board. And when you’re designing for real-world environments—temperature changes, power surges, and tight layouts—the careful handling of unit prefixes becomes part of your design intuition.

Takeaway

350,000 nH is the same as 350 μH. Remember the 1 μH = 1000 nH rule, keep an eye on tolerance and SRF, and you’ll navigate SMT inductors with confidence. The math is simple, but the impact on performance is anything but.