LNK302/304-306

LinkSwitch-TN

Family

Lowest Component Count, Energy Efficient

Off-Line Switcher IC

Figure 1. Typical Buck Converter Application (See Application

Examples Section for Other Circuit Configurations).

Product Highlights

Cost Effective Linear/Cap Dropper Replacement

• Lowest cost and component count buck converter solution

• Fully integrated auto-restart for short-circuit and open

loop fault protection – saves external component costs

• LNK302 uses a simplified controller without auto-restart

for very low system cost

• 66 kHz operation with accurate current limit – allows low cost

off-the-shelf 1 mH inductor for up to 120 mAoutput current

• Tight tolerances and negligible temperature variation

• High breakdown voltage of 700 V provides excellent

input surge withstand

• Frequency jittering dramatically reduces EMI (~10 dB)

– minimizes EMI filter cost

• High thermal shutdown temperature (+135 °C minimum)

Much Higher Performance over Discrete Buck and

Passive Solutions

• Supports buck, buck-boost and flyback topologies

• System level thermal overload, output short-circuit and

open control loop protection

• Excellent line and load regulation even with typical

configuration

• High bandwidth provides fast turn-on with no overshoot

• Current limit operation rejects line ripple

• Universal input voltage range (85 VAC to 265 VAC)

• Built-in current limit and hysteretic thermal protection

• Higher efficiency than passive solutions

• Higher power factor than capacitor-fed solutions

• Entirely manufacturable in SMD

– Extremely Energy Efficient

• Consumes typically only 50/80 mW in self-powered buck

topology at 115/230 VAC input with no load (opto feedback)

• Consumes typically only 7/12 mW in flyback topology

with external bias at 115/230 VAC input with no load

• Meets California Energy Commission (CEC), Energy

Star, and EU requirements

Applications

• Appliances and timers

• LED drivers and industrial controls

Description

LinkSwitch-TN

is specifically designed to replace all linear and

capacitor-fed (cap dropper) non-isolated power supplies in the

®

Table 1.

Notes: 1. Typical output current in a non-isolated buck

converter. Output power capability depends on respective output

voltage. See Key Applications Considerations Section for complete

description of assumptions, including fully discontinuous conduction

mode (DCM) operation. 2. Mostly discontinuous conduction mode. 3.

Continuous conduction mode. 4. Packages: P: DIP-8B, G: SMD-8B.

For lead-free package options, see Part Ordering Information.

under 360 mA output current range at equal system cost while

offering much higher performance and energy efficiency.

LinkSwitch-TN

devices integrate a 700 V power MOSFET,

oscillator,simpleOn/Offcontrolscheme,ahighvoltageswitched

current source, frequency jittering, cycle-by-cycle current limit

and thermal shutdown circuitry onto a monolithic IC. The start-

up and operating power are derived directly from the voltage

on the DRAIN pin, eliminating the need for a bias supply and

associated circuitry in buck or flyback converters. The fully

integrated auto-restart circuit in the LNK304-306 safely limits

output power during fault conditions such as short-circuit or

open loop, reducing component count and system-level load

protection cost. A local supply provided by the IC allows use

of a non-safety graded optocoupler acting as a level shifter to

further enhance line and load regulation performance in buck

and buck-boost converters, if required.

March 2005

230 VAC ±15%

85-265 VAC

LNK302P or G 63 mA

80 mA

63 mA 80 mA

LNK304P or G 120 mA 170 mA 120 mA 170 mA

LNK305P or G 175 mA 280 mA 175 mA 280 mA

LNK306P or G 225 mA 360 mA 225 mA 360 mA

DC

Output

Wide Range

HV DC Input

PI-3492-111903

+

+

FB

BP

S

D

LinkSwitch-TN