LNK364DN-TL — 9W Off-Line Flyback Switcher, Self-Powered, Optocoupler Feedback (SO-8C)

What Are the Technical Specifications of LNK364DN?

Key numbers that matter: the 700V BVDSS is an absolute maximum, not a target — Power Integrations' own guidance is to keep drain voltage under 650V in all transient conditions.

And the 233–268mA current limit is the real power spec: it's what caps the 6W universal-input rating.

The SO-8C pin map: four of the eight pads are SOURCE — they're the ground reference and heatsink path — and the three signal terminals are BYPASS (pin 3), FEEDBACK (pin 4), and DRAIN (pin 5). Pin 6 is the only no-connect.

Getting BP and FB swapped is the classic first-board mistake.

When Should You Use (and NOT Use) the LNK364DN?

✅ Use LNK364DN when:

• 2–6W universal-input isolated supplies. Appliance standby rails, smart-home wall pods, utility-meter supplies — the classic LinkSwitch-XT territory.
• Replacing a 50/60Hz linear transformer. Same output role, a fraction of the copper and heat, plus line and load regulation the transformer never had.
• Your team knows optocoupler loops. The FB pin wants an opto plus TL431 — if that's your comfort zone, no new architecture to learn.
• No room for a bias winding. Self-powered from DRAIN means the transformer is simpler and smaller.

❌ Don't use LNK364DN when:

• You need more than 6W at universal input. Step up to a TinySwitch TNY284DG (5W, tighter regulation) or jump to the INN3676C for 20–40W.
• Isolation isn't required. For a non-isolated buck, the LNK306 is the right part — and no, they don't swap (see FAQ).
• You want no optocoupler at all. A LinkSwitch-LP LNK562DN does primary-side regulation without a secondary loop — at 3W.
• Output regulation must stay tight across full load range. On/off control with an opto loop is solid, but a TinySwitch-4 with its higher feedback gain is the tighter option when every millivolt counts.

What Are the Alternatives to LNK364DN?

The LinkSwitch-XT power ladder at 85–265VAC: one die, three current limits — the 233–268mA limit in the LNK364 is what buys the 6W universal-input rating that the smaller siblings can't reach.

LNK364DN vs TNY284DG — the regulation question. Both are isolated flybacks with opto loops in SO-8C. The TNY284's stronger feedback path buys tighter output regulation and line-compensated current limiting; the LNK364 counters with self-powering and a simpler transformer.

For a 5W rail with a picky load, TNY284. For a 6W standby supply where simplicity wins, LNK364.

LNK364DN vs LNK562DN — opto or no opto? The LNK562 deletes the opto and TL431 by regulating from the primary side — fewer parts, but a looser tolerance and no secondary feedback of any kind.

At 3W that trade usually favors the LNK562. At 6W, the LNK364's real output sensing is worth the two extra components.

What Are the Typical Applications of LNK364DN?

The standard 6W flyback in one picture: primary winding driven by DRAIN, secondary rectified to Vout, and a PC817-class opto with a TL431 closing the loop back to the FB pin. No bias winding anywhere.

Appliance standby and control rails: The LNK364's 6W universal-input rating fits the control boards of washing machines, dishwashers, and cooktops, where the supply spends most of its life at a few hundred milliwatts and must wake instantly.

Utility metering and smart-grid nodes: Long-life equipment with no servicing window favors a loop with no exotic parts — an opto, a TL431, and an electrolytic are repairable anywhere on the planet.

Small battery chargers: The on/off control plus current limiting gives a usable CC/CV charging profile for 2–3-cell NiMH or single-cell Li-ion at low currents without a dedicated charger IC.

Linear transformer replacement: Doorbells, timers, thermostat power, small motor controls — anywhere a 50/60Hz transformer sits, the LNK364 delivers the same rail with regulation and short-circuit protection.

Why Buy LNK364DN from ICMASS?

Stocked with the family, not just one part. The LNK362, LNK363, and LNK364 share one transformer design footprint — we keep all three current limits on the shelf, so a power bump mid-project doesn't wait for a new order.

Genuine Power Integrations parts. LinkSwitch parts are counterfeited often enough that the 700V rating can't be assumed. We source from authorized channels and can provide lot traceability on request.

Cross-reference support. Replacing an LNK306, moving up from an LNK363, or deciding between LNK364 and TNY284 — tell us the input range, output, and regulation spec, and we'll confirm the right family before you order.

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 LNK364DN

Q1: Can I replace an LNK306 with an LNK364?

A: No — they're different families with different topologies. The LNK306 is a LinkSwitch-TN non-isolated buck; the LNK364 is a LinkSwitch-XT isolated flyback. Power Integrations' forum has a documented case where the swap caused startup problems and excess heat. They're not interchangeable in either direction.

Q2: Why is the LNK364 rated 9W but only about 6W works at universal input?

A: The 9W figure assumes 230VAC ±15%. At 85–265VAC the lower line voltage and the part's 233–268mA current limit cap the practical output around 6W open frame. Plan the design for 6W unless the input is guaranteed high-line.

Q3: Do I need an auxiliary bias winding?

A: No — the LNK364 is self-powered. The controller draws its operating current from the DRAIN pin, so the transformer has no bias winding. Fewer windings, smaller transformer, less to get wrong.

Q4: What goes on the FB and BP pins?

A: FB takes the optocoupler output; BP takes a 0.1µF bypass capacitor. A Power Integrations design-verification thread flagged both: feedback components must land on the FB pin (pin 4), and the 0.1µF cap must sit directly between BYPASS and SOURCE. Getting them swapped is the classic first-board fault.

Q5: Why do a few chips from the same lot run hot or trip thermal shutdown?

A: One documented case traced it to out-of-spec switch-off current — 320mA versus the 268mA limit. In a PI forum thread, 2 of about 100 parts from one lot entered thermal shutdown after 10–20 seconds while the rest ran normally. If a board runs hot, measure the drain current and check assembly quality before blaming the design.

Q6: How much drain voltage margin do I need?

A: Keep VDS under 650V in all transients — the 700V BVDSS is an absolute maximum. PI's guidance after a PFC front-end case that pushed drain voltage to 706V for 25ns: verify the clamp and transformer ratio, and measure with a properly compensated probe. Margin lives in the snubber.

Q7: Are LNK362, LNK363, and LNK364 interchangeable?

A: Mechanically yes, electrically no. All three share the same die and package, but current limits differ — 130–150mA (LNK362), 195–225mA (LNK363), 233–268mA (LNK364). The limit sets the power capability, so each part needs its own transformer check.

Q8: What switching frequency does the LNK364 run at?

A: 132kHz typical, 124–140kHz across the range, with frequency jittering. The jitter deliberately spreads switching energy across the spectrum, which flattens EMI peaks and eases filter design — a quiet gift for a 6W part.

Q9: What feedback components does a 5V LNK364 supply need?

A: A PC817-class optocoupler, a TL431, and a handful of resistors. The TL431 senses the output, drives the opto LED, and the opto transistor pulls the FB pin. It's the same loop used across the entire opto-feedback AC-DC world — and the reason the TL431 appears on so many BOMs.

Q10: Can the LNK364 drive a dual-output supply?

A: Yes, with the regulation on one output. A PI forum design verification covered a 12V/5V LNK364PN supply: the loop regulates the primary output, and the secondary rail follows with wider tolerance unless you add weighting or post-regulation.