LNK304PN vs TNY274PN vs TOP224YN - Three Power Integrations Families, Three Design Philosophies

Power Integrations makes over a dozen offline switcher families, but three of them cover probably 80% of sub-100W designs you'll encounter: LinkSwitch-TN, TinySwitch-III, and TOPSwitch-II. They're not just different power ratings of the same thing - they have fundamentally different control architectures, package philosophies, and design trade-offs. Here's how to pick.

How Do LNK304PN, TNY274PN, and TOP224YN Compare on Key Parameters?

Are LNK304PN, TNY274PN, and TOP224YN Pin-Compatible?

No. They are not pin-compatible - not even close.

• LNK304PN uses a DIP-7 package. Pins: DRAIN (5), SOURCE (1,2,3,4,7,8 - six pins tied together), FB (6). Four SOURCE pins on one side for low-inductance grounding.
• TNY274PN uses a DIP-8C package. Pins: DRAIN (5), SOURCE (1,2,3,4,7,8 - six pins tied), EN/UV (6), BP/M (internal). Same DRAIN pin position (pin 5), but the control pin function is completely different: digital enable vs analog feedback voltage.
• TOP224YN uses a TO-220-3 package. Three pins: DRAIN (1), SOURCE (2), CONTROL (3). Totally different footprint.

Bottom line: You can't drop one into another's PCB footprint. These are three separate board layouts. If you need pin-compatible power scaling within the same family:

• Within LinkSwitch-TN: LNK302PN → LNK304PN → LNK305PN → LNK306PN (all DIP-7, same pinout)
• Within TinySwitch-III: TNY273PN → TNY274PN → TNY275PN → TNY276PN → TNY277PN → TNY278PN (all DIP-8C, same pinout)
• Within TOPSwitch-II: TOP223YN → TOP224YN → TOP225YN → TOP226YN → TOP227YN (all TO-220-3, same pinout)

When to Choose LNK304PN

You're building a non-isolated supply and the load is under 120mA. This is the LinkSwitch-TN's home turf. Buck converter - one chip, one inductor, one diode, two resistors, two caps. No transformer, no optocoupler, no bias winding. If your MCU, relay coil, or sensor node just needs a clean DC rail from the mains and isolation isn't required, the LNK304PN is the cheapest and simplest way to get there.

Standby power is the #1 spec. 50mW no-load at 115VAC. For appliances that spend 99% of their life in standby - smart plugs, IoT sensors, IR remote receivers - the LNK304's cycle-skipping control naturally draws almost nothing when the load goes to zero.

You need something an intern can lay out. The buck topology is forgiving. The feedback network is two resistors. The freewheeling diode is the only component that can really bite you. Compared to a flyback with transformer design, RCD clamp tuning, and optocoupler compensation - the LNK304PN is an afternoon project, not a week-long design cycle.

You're replacing a capacitor dropper or linear regulator. If you have an existing design using a resistive dropper or a 7805 linear regulator running hot off rectified mains, swapping to an LNK304PN buck converter cuts heat by 80%+ and meets modern energy standards. Same PCB area, usually.

Cost is the dominant constraint. Under $0.40 in volume. When the BOM for the entire power supply - chip, inductor, diode, caps, resistors - needs to come in under $1.50, the LNK304PN in buck configuration is hard to beat.

When to Choose TNY274PN

You need galvanic isolation. This is the deciding factor. If your output must be isolated from mains for safety - a USB charger someone touches, a medical device, any consumer product with exposed connectors - the TNY274PN's flyback topology with a transformer is the answer.

Your load is 3-15 watts. The TNY274PN hits the sweet spot at 8.5W universal, with the TNY275 (11.5W) and TNY276 (15W) covering the upper end of this range without changing packages.

Standby regulations are tight but you can add a bias winding. With a bias winding, the TNY274PN gets under 50mW no-load - competitive with the LNK304PN but with the benefit of isolation.

You want one PCB for multiple power levels. The BP/M pin capacitor trick - 0.1µF = 250mA, 1µF = 275mA, 10µF = 300mA - means one PCB layout can serve 6W, 8.5W, and 11W product variants by changing two BOM lines.

You're designing for production, not just prototyping. The DIP-8C package works for both through-hole prototyping and has an SMD equivalent (TNY274GN) for reflow assembly.

When to Choose TOP224YN

You need more than 20 watts and you need it isolated. The TOP224YN delivers 45W on universal input, 75W on 230VAC-only. Neither the LNK304PN (1.4W buck) nor the TNY274PN (8.5W) comes close. If your design is a 30W battery charger, a 50W audio amplifier supply, or a 60W industrial SMPS - you're in TOPSwitch territory.

You're bolting the supply to a metal chassis anyway. The TO-220 package's exposed tab is electrically SOURCE - bolt it directly to a grounded chassis and you get free heatsinking. No insulator needed.

You're maintaining an existing qualified design. If the product was designed, tested, EMI-certified, and safety-approved with a TOP224YN, replacing it with a newer-generation part means re-certification. The TOP224YN is still in full production. Don't fix what isn't broken.

You want the simplest possible control loop. Three pins. One control pin. The entire feedback loop is the current drawn from the CONTROL pin by an optocoupler. No EN/UV thresholds, no BP/M capacitor selection, no configuration options.

The latching thermal shutdown is a feature, not a bug. In industrial environments, you want a supply that stays off after an over-temperature event until a technician investigates - not one that cycles on and off while the root cause festers.

Why Buy from ICMASS?

All three families, one supplier. LinkSwitch-TN, TinySwitch-III, and TOPSwitch-II - we stock the full power gradient in each family. One purchase order covers your low-power non-isolated rails, your mid-power flyback adapters, and your high-power chassis-mount supplies.

Genuine parts with batch traceability. PI chips are widely counterfeited, especially the older TOPSwitch-II series. We source from authorized distribution and log lot codes on every tube.

Shenzhen stock, same-day shipping. Orders before 4PM HKT ship same day. DHL 3-5 days worldwide.

We know these parts. If you're torn between an LNK306 and a TNY274 for a borderline design, ask us. We've seen which way most customers go and why.

Frequently Asked Questions

Q1: Can I use an LNK304PN for an isolated flyback design?

A: Technically yes - the LNK304PN datasheet includes a flyback topology section. But the TinySwitch-III (TNY274PN) is a much better flyback controller: the EN/UV pin gives you undervoltage lockout, the BP/M pin lets you adjust current limit, and the 132kHz switching frequency lets you use a smaller transformer. If you need isolation, use the TNY274PN. The LNK304PN's strength is non-isolated buck - that's what it was designed for.

Q2: Can I use a TNY274PN without a transformer (non-isolated buck)?

A: Yes, but you shouldn't. The TNY274PN can do buck in theory, but the LNK304PN does it better - simpler feedback (1.65V threshold vs 240µA digital threshold), lower switching frequency (66kHz vs 132kHz, easier to lay out), and it's cheaper. Use the right tool for the topology.

Q3: What's the actual efficiency difference between these three?

A: At their respective sweet spots: LNK304PN buck at 12V/100mA ≈ 75-80%. TNY274PN flyback at 12V/0.7A ≈ 82-85%. TOP224YN flyback at 24V/2A ≈ 85-90%. These are rough numbers - efficiency depends heavily on transformer design, diode selection, and whether you use a bias winding. The TOP224YN has the highest efficiency ceiling because it operates at higher power where fixed losses are a smaller percentage of total power.

Q4: Why does the TOP224YN have latching thermal shutdown while the others auto-recover?

A: Different design philosophies from different eras. TOPSwitch-II was designed in the mid-1990s for TV and monitor power supplies - applications where a thermal shutdown means something is seriously wrong and you want the unit to stay off until repaired. LinkSwitch-TN and TinySwitch-III were designed later for appliances and adapters where a temporary thermal excursion should self-clear. If you need auto-recovery in a TO-220 power switcher, use TOPSwitch-GX (TOP244YN).

Q5: Which one has the lowest standby power?

A: TNY274PN with a bias winding: <50mW at 265VAC. LNK304PN is close: 50-80mW depending on line voltage and feedback configuration. TOP224YN is the highest - the 100kHz PWM oscillator runs continuously even at no-load. Standby power wasn't a regulatory concern when TOPSwitch-II was designed.

Q6: Can I drive all three from the same rectified DC bus?

A: Yes - all three accept 85-265VAC rectified to DC. The TOP224YN needs a higher DC bus voltage for full power (the 75W rating assumes 230VAC → ~325VDC). At lower DC bus voltages, all three deliver proportionally less power.

Q7: Which one is easiest to prototype on a breadboard?

A: LNK304PN. Buck topology, through-hole DIP-7, six SOURCE pins tied together for easy grounding. No transformer to wind, no optocoupler to compensate. TNY274PN is next - DIP-8C but needs a flyback transformer. TOP224YN is trickiest on a breadboard because the TO-220 pins are thicker, and at 45-75W you're dealing with voltages and currents where breadboard contacts aren't reliable.

Q8: The TOP224YN is "Not Recommended for New Designs" - should I avoid it?

A: For new designs starting today: yes, use TOP244YN (TOPSwitch-GX) or TOP254EN (TOPSwitch-HX) instead. They're more efficient, have more protection features, and are the recommended upgrade path. For maintaining an existing product already qualified with TOP224YN: keep using it. The part is in full production, widely available, and changing it means re-certification.

Q9: What's the one-sentence rule for choosing between these three?

A: Non-isolated and under 3W → LNK304PN. Isolated and 3-20W → TNY274PN (or its power siblings TNY273-TNY278). Isolated and 20-100W → TOP224YN (or its power siblings TOP223-TOP227).

Q10: Do you stock the full power gradient of each family?

A: Yes. LinkSwitch-TN: LNK302 through LNK306. TinySwitch-III: TNY273 through TNY278. TOPSwitch-II: TOP221 through TOP227. All three package types per family where applicable. Contact us for volume pricing across the gradient if you're designing a product family at multiple power tiers.