LNK306DG-TL — 225mA Non-Isolated Buck Converter IC (SO-8C)

What Are the Technical Specifications of LNK306DG-TL?

Key numbers that matter: The 7Ω R_DS(ON) is what separates the LNK306 from its smaller siblings. At 482mA I_LIMIT, conduction loss (I²R) peaks around 1.6W — manageable with adequate copper pour. A 1mH buck inductor at 66kHz gives ~30% ripple at 12V output.

When Should You Use (and NOT Use) the LNK306DG-TL?

✅ Use LNK306DG-TL when:

• You need a non-isolated offline supply with 150–250mA output. The LNK306 in buck topology converts 85–265VAC to a regulated DC rail with about a dozen passives. No transformer, no optocoupler, no auxiliary winding.
• You're pushing past an LNK304's current limit. The LNK304 tops out around 170mA in CCM. Swapping to an LNK306 gives you 360mA in the same footprint — but verify the inductor saturation current can handle the higher peak.
• Appliance standby supplies and e-meter power boards. The LinkSwitch-TN family is the reference design inside millions of smart meters, rice cookers, and AC fans. The LNK306 covers the higher end of standby power where the MCU draws more than a trickle.
• Industrial sensor nodes running from 24VAC. Full-wave rectify 24VAC to ~34VDC, buck it to 3.3V or 5V with the LNK306 — compact, reliable, no heatsink needed below 200mA load.

❌ Don't use LNK306DG-TL when:

• You need galvanic isolation. LinkSwitch-TN is non-isolated by design. For isolated supplies, look at TinySwitch-III (TNY274–280) or LinkSwitch-II (LNK623–626) with a coupled inductor or flyback transformer.
• Output current above 360mA. The LNK306 hits its current limit wall in CCM at about 360mA. For 500mA+, step up to TNY284 (TinySwitch-4, 500mA) or a discrete PWM controller.
• Audible noise is a hard requirement (silent operation). The 66kHz switching frequency and cycle-skipping at light load can produce audible inductor whine. The newer LinkSwitch-TN2 family addresses this with higher switching frequency and improved jitter. If you're locked into LNK306, add a series resistor (~47Ω) in the feedback path to damp the loop.
• You need sub-20mW no-load standby. LinkSwitch-TN draws about 50–80mW unloaded. For tighter standby budgets, LinkSwitch-XT or TinySwitch-4 offer lower no-load consumption.

LNK304 vs LNK305 vs LNK306 — How Do They Compare?

All three share the same 700V MOSFET, 66kHz frequency, SO-8C package, and auto-restart protection. The difference is how much current the internal MOSFET can carry before hitting its limit.

So which one? The LNK304 covers low-power standby rails (≤120mA). Jump to the LNK305 at 150–200mA. Reach for the LNK306 when you need 200–360mA or want the thermal margin of lower R_DS(ON). One caveat: the LNK306's higher I_LIMIT can saturate an inductor sized for an LNK304 — check I_SAT before swapping.

Pin Functions at a Glance

What Are the Typical Applications of LNK306DG-TL?

Non-isolated appliance standby supply (12V/200mA). A dozen components — fuse, bridge rectifier, input cap, buck inductor, freewheeling diode, output cap, feedback resistors, and the LNK306 — build a complete 12V rail from universal AC. No auxiliary winding. The auto-restart feature means a shorted output just hiccups until the fault clears.

Smart meter / e-meter power supply (3.3V/150mA). Millions of electricity meters use LinkSwitch-TN to power the MCU, display, and RF module from the AC line being measured. The LNK306 covers the higher end — always-on wireless (Zigbee, Wi-SUN) pushes standby current past what an LNK304 can deliver.

Industrial 24VAC sensor node (5V/200mA). Factory automation runs on 24VAC. Full-wave rectify to ~34VDC, buck to 5V with LNK306 — the 700V MOSFET easily handles line transients. Add a TVS across the input for surge protection and you've got a supply that fits in a sensor housing.

LED driver (constant-current buck, 80–150mA). Configure the FB pin with a current-sense resistor instead of a voltage divider, and the LNK306 becomes a constant-current LED driver. The 66kHz switching keeps inductor size small enough for GU10 bulb form factors. Useful for low-cost, non-dimmable LED bulbs where isolation isn't required.

What Are the Alternatives to LNK306DG-TL?

LNK306 vs TNY284 — non-isolated or isolated? The LNK306 buck needs no transformer — cheaper BOM, smaller footprint, no isolation. The TNY284 flyback gives you safety isolation and more power, at higher magnetics cost.

If your load floats at line potential (appliance internals), the LNK306 saves cost. If a human can touch the output, you need isolation — use the TNY284.

How Much Does the LNK306DG-TL Cost and Is It in Stock?

Contact ICMASS for a same-day quote on your specific quantity. The LNK306DG-TL is an active production part with stable multi-source availability. It's typically 2–3× the price of an LNK304 at the same quantity — you're paying for the larger die area that delivers the lower R_DS(ON) and higher current limit.

Why Buy LNK306DG-TL from ICMASS?

We stock the full LinkSwitch-TN family in one place. If you're prototyping with an LNK304 and find you need more current, we have LNK305 and LNK306 on the shelf — same package, same footprint, same day shipping. No need to re-spin the PCB for a larger part.

Cross-reference support for non-isolated designs. Tell us your input voltage range, output voltage, and load current. We'll tell you whether the LNK306 fits, or whether you need to step up to TinySwitch for isolation or LinkSwitch-II for CC/CV output. No datasheet translation required.

BOM consolidation for power supply builds. The LNK306 needs a buck inductor, a freewheeling diode (UF4007 or similar fast-recovery), input and output capacitors, and a few resistors. We stock all of them — one shipment, one set of shipping docs.

Shenzhen warehouse, global DHL/FedEx. Same-day shipping for orders placed before 15:00 CST. International delivery in 5–10 days.

Frequently Asked Questions About LNK306DG-TL

Q1: Can I drop an LNK306 into a board designed for LNK304?

A: Electrically yes — same pinout, same SO-8C footprint. But check your inductor's saturation current first. The LNK306's I_LIMIT is 482mA versus the LNK304's 257mA. If your inductor saturates at 350mA, the LNK306 will drive it into saturation on every cycle, and the resulting current spikes will cook both the inductor and the IC.

Q2: Why is my LNK306 making an audible whistling noise?

A: Cycle-skipping at light load is the most common cause. At 66kHz, the inductor can vibrate audibly through magnetostriction when the IC skips cycles to maintain regulation. The fix: add a 47–100Ω series resistor in the feedback path to damp the control loop. If that doesn't silence it, try a different inductor with tighter winding or consider upgrading to LinkSwitch-TN2, which addresses this with higher switching frequency.

Q3: How much PCB copper area does the LNK306 need?

A: 50mm² minimum, 100mm² recommended for full output. The SOURCE pins are the only thermal path out of the die. At 225mA output from 230VAC, a 50mm² copper pour keeps junction temperature around 85–95°C. At 360mA in CCM, you need closer to 100mm². If your board is too compact, expect thermal shutdown cycling — the IC hits ~142°C, shuts off, cools down, and restarts.

Q4: LNK306DG-TL vs LNK306DN-TL — what's the difference?

A: Package height. DG is 1.43mm max; DN is 1.75mm max. Same die, same electrical specs, same SO-8C footprint. The DG variant is the lower-profile option. In practice, the two are interchangeable for most designs — pick whichever your assembler has on the reel.

Q5: Can the LNK306 do a buck-boost or inverting supply?

A: Yes — the same IC works in buck, buck-boost, and flyback topologies. Power Integrations' DER-49 reference design shows a buck-boost configuration producing 12V from universal AC. The catch: in buck-boost, the output current capability drops to about 60–70% of the buck-mode rating. Plan for 140–160mA max in buck-boost.

Q6: What causes my LNK306 supply to go into auto-restart?

A: Output capacitor too small. If the output cap charges too fast or the feedback loop is unstable, the IC enters auto-restart (50ms on, ~750ms off, repeating). Increase the output capacitor to at least 100µF. Also verify the BP capacitor is a 100nF ceramic right at the BP and SOURCE pins — long traces cause noise injection.

Q7: Is the LNK306 DG-TL RoHS compliant?

A: Yes. All current-production LinkSwitch-TN parts in SO-8C are RoHS-compliant and lead-free. The "-TL" suffix denotes tape-and-reel packaging (2,500 units per reel).

Q8: Can I use LNK306 for a 5V USB charger?

A: Don't — USB outputs need isolation. The LNK306 is non-isolated, meaning the output ground sits at line potential relative to earth. For any supply where a human can touch the output connector, you need galvanic isolation. Use a TinySwitch or LinkSwitch-II part instead.