LNK304PN - Power Integrations, Inc.

Table 1. Output Current Table.

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, D: SO-8C.

LNK302/304-306

LinkSwitch-TN Family

Lowest Component Count, Energy-Efﬁ cient

Off-Line Switcher IC

Figure 1. Typical Buck Converter Application (See Application

Examples Section for Other Circuit Conﬁ gurations).

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 simpliﬁ ed 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 mA output 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 ﬁ lter cost

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

Much Higher Performance over Discrete Buck and

Passive Solutions

• Supports buck, buck-boost and ﬂ yback topologies

• System level thermal overload, output short-circuit and

open control loop protection

• Excellent line and load regulation even with typical

conﬁ guration

• 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 efﬁ ciency than passive solutions

• Higher power factor than capacitor-fed solutions

• Entirely manufacturable in SMD

EcoSmart®– Extremely Energy Efﬁ cient

• 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 ﬂ yback 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 speciﬁ cally designed to replace all linear and

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

under 360 mA output current range at equal system cost while

offering much higher performance and energy efﬁ ciency.

LinkSwitch-TN devices integrate a 700 V power MOSFET,

oscillator, simple On/Off control scheme, a high voltage switched

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 ﬂ yback 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.

November 2008

OUTPUT CURRENT TABLE1

PRODUCT4230 VAC ±15% 85-265 VAC

MDCM2CCM3MDCM2CCM3

LNK302P/G/D 63 mA 80 mA 63 mA 80 mA

LNK304P/G/D 120 mA 170 mA 120 mA 170 mA

LNK305P/G/D 175 mA 280 mA 175 mA 280 mA

LNK306P/G/D 225 mA 360 mA 225 mA 360 mA

Output

Wide Range

HV DC Input

PI-3492-111903

FB BP

LinkSwitch-TN

2-2

Rev. I 11/08

LNK302/304-306

Figure 2a. Functional Block Diagram (LNK302).

PI-2367-021105

CLOCK

JITTER

OSCILLATOR

5.8 V

4.85 V

SOURCE

(S)

DCMAX

BYPASS

(BP)

FAULT

PRESENT

VILIMIT

LEADING

EDGE

BLANKING

THERMAL

SHUTDOWN

DRAIN

(D)

REGULATOR

5.8 V

BYPASS PIN

UNDER-VOLTAGE

CURRENT LIMIT

COMPARATOR

FEEDBACK

(FB)

6.3 V

RESET

AUTO-

RESTART

COUNTER

1.65 V -VT

CLOCK

Figure 2b. Functional Block Diagram (LNK304-306).

PI-3904-020805

CLOCK

JITTER

OSCILLATOR

5.8 V

4.85 V

SOURCE

(S)

DCMAX

BYPASS

(BP)

VILIMIT

LEADING

EDGE

BLANKING

THERMAL

SHUTDOWN

DRAIN

(D)

REGULATOR

5.8 V

BYPASS PIN

UNDER-VOLTAGE

CURRENT LIMIT

COMPARATOR

FEEDBACK

(FB)

6.3 V

1.65 V -VT

2-3

LNK302/304-306

Rev. I 11/08

Pin Functional Description

DRAIN (D) Pin:

Power MOSFET drain connection. Provides internal operating

current for both start-up and steady-state operation.

BYPASS (BP) Pin:

Connection point for a 0.1 μF external bypass capacitor for the

internally generated 5.8 V supply.

FEEDBACK (FB) Pin:

During normal operation, switching of the power MOSFET is

controlled by this pin. MOSFET switching is terminated when

a current greater than 49 μA is delivered into this pin.

SOURCE (S) Pin:

This pin is the power MOSFET source connection. It is also the

ground reference for the BYPASS and FEEDBACK pins.

LinkSwitch-TN Functional

Description

LinkSwitch-TN combines a high voltage power MOSFET switch

with a power supply controller in one device. Unlike conventional

PWM (pulse width modulator) controllers, LinkSwitch-TN uses

a simple ON/OFF control to regulate the output voltage. The

LinkSwitch-TN controller consists of an oscillator, feedback

(sense and logic) circuit, 5.8 V regulator, BYPASS pin under-

voltage circuit, over-temperature protection, frequency jittering,

current limit circuit, leading edge blanking and a 700 V power

MOSFET. The LinkSwitch-TN incorporates additional circuitry

for auto-restart.

Oscillator

The typical oscillator frequency is internally set to an average

of 66 kHz. Two signals are generated from the oscillator: the

maximum duty cycle signal (DCMAX) and the clock signal that

indicates the beginning of each cycle.

The LinkSwitch-TN oscillator incorporates circuitry that

introduces a small amount of frequency jitter, typically 4 kHz

peak-to-peak, to minimize EMI emission. The modulation rate

of the frequency jitter is set to 1 kHz to optimize EMI reduction

for both average and quasi-peak emissions. The frequency

jitter should be measured with the oscilloscope triggered at

the falling edge of the DRAIN waveform. The waveform in

Figure 4 illustrates the frequency jitter of the LinkSwitch-TN.

Feedback Input Circuit

The feedback input circuit at the FB pin consists of a low

impedance source follower output set at 1.65 V. When the current

delivered into this pin exceeds 49 μA, a low logic level (disable)

is generated at the output of the feedback circuit. This output

is sampled at the beginning of each cycle on the rising edge of

the clock signal. If high, the power MOSFET is turned on for

that cycle (enabled), otherwise the power MOSFET remains off

(disabled). Since the sampling is done only at the beginning of

each cycle, subsequent changes in the FB pin voltage or current

during the remainder of the cycle are ignored.

5.8 V Regulator and 6.3 V Shunt Voltage Clamp

The 5.8 V regulator charges the bypass capacitor connected to

the BYPASS pin to 5.8 V by drawing a current from the voltage

on the DRAIN, whenever the MOSFET is off. The BYPASS

pin is the internal supply voltage node for the LinkSwitch-TN.

When the MOSFET is on, the LinkSwitch-TN runs off of the

energy stored in the bypass capacitor. Extremely low power

consumption of the internal circuitry allows the LinkSwitch-TN

to operate continuously from the current drawn from the DRAIN

pin. A bypass capacitor value of 0.1 μF is sufﬁ cient for both

high frequency decoupling and energy storage.

In addition, there is a 6.3 V shunt regulator clamping the

BYPASS pin at 6.3 V when current is provided to the BYPASS

pin through an external resistor. This facilitates powering of

LinkSwitch-TN externally through a bias winding to decrease

the no-load consumption to about 50 mW.

BYPASS Pin Under-Voltage

The BYPASS pin under-voltage circuitry disables the power

MOSFET when the BYPASS pin voltage drops below 4.85 V.

Once the BYPASS pin voltage drops below 4.85 V, it must rise

back to 5.8 V to enable (turn-on) the power MOSFET.

Over-Temperature Protection

The thermal shutdown circuitry senses the die temperature.

The threshold is set at 142 °C typical with a 75 °C hysteresis.

When the die temperature rises above this threshold (142 °C) the

power MOSFET is disabled and remains disabled until the die

temperature falls by 75 °C, at which point it is re-enabled.

Current Limit

The current limit circuit senses the current in the power MOSFET.

When this current exceeds the internal threshold (ILIMIT), the

PI-3491-120706

3a 3b

FB D

P Package (DIP-8B)

G Package (SMD-8B) D Package (SO-8C)

D S

FB S

BP 8

Figure 3. Pin Conﬁ guration.

2-4

Rev. I 11/08

LNK302/304-306

Figure 5. Universal Input, 12 V, 120 mA Constant Voltage Power Supply Using LinkSwitch-TN.

power MOSFET is turned off for the remainder of that cycle.

The leading edge blanking circuit inhibits the current limit

comparator for a short time (tLEB) after the power MOSFET

is turned on. This leading edge blanking time has been set so

that current spikes caused by capacitance and rectiﬁ er reverse

recovery time will not cause premature termination of the

switching pulse.

Auto-Restart (LNK304-306 only)

In the event of a fault condition such as output overload, output

short, or an open loop condition, LinkSwitch-TN enters into auto-

restart operation. An internal counter clocked by the oscillator

gets reset every time the FB pin is pulled high. If the FB pin

is not pulled high for 50 ms, the power MOSFET switching is

disabled for 800 ms. The auto-restart alternately enables and

disables the switching of the power MOSFET until the fault

condition is removed.

Applications Example

A 1.44 W Universal Input Buck Converter

The circuit shown in Figure 5 is a typical implementation of a

Figure 4. Frequency Jitter.

RTN

12 V,

120 mA

85-265

VAC

PI-3757-112103

FB BP

LinkSwitch-TN

4.7 μF

400 V

100 nF

1N4007

UF4005

LNK304

1N4005GP

100 μF

16 V

RF1

8.2 Ω

2 W

13.0 kΩ

2.05 kΩ

1 mH

280 mA

4.7 μF

400 V

10 μF

35 V

3.3 kΩ

12 V, 120 mA non-isolated power supply used in appliance

control such as rice cookers, dishwashers or other white goods.

This circuit may also be applicable to other applications such

as night-lights, LED drivers, electricity meters, and residential

heating controllers, where a non-isolated supply is acceptable.

The input stage comprises fusible resistor RF1, diodes D3 and

D4, capacitors C4 and C5, and inductor L2. Resistor RF1 is

a ﬂ ame proof, fusible, wire wound resistor. It accomplishes

several functions: a) Inrush current limitation to safe levels for

rectiﬁ ers D3 and D4; b) Differential mode noise attenuation;

c) Input fuse should any other component fail short-circuit

(component fails safely open-circuit without emitting smoke,

ﬁ re or incandescent material).

The power processing stage is formed by the LinkSwitch-TN,

freewheeling diode D1, output choke L1, and the output

capacitor C2. The LNK304 was selected such that the power

supply operates in the mostly discontinuous-mode (MDCM).

Diode D1 is an ultra-fast diode with a reverse recovery time (trr)

of approximately 75 ns, acceptable for MDCM operation. For

continuous conduction mode (CCM) designs, a diode with a trr of

≤35 ns is recommended. Inductor L1 is a standard off-the- shelf

inductor with appropriate RMS current rating (and acceptable

temperature rise). Capacitor C2 is the output ﬁ lter capacitor;

its primary function is to limit the output voltage ripple. The

output voltage ripple is a stronger function of the ESR of the

output capacitor than the value of the capacitor itself.

To a ﬁ rst order, the forward voltage drops of D1 and D2 are

identical. Therefore, the voltage across C3 tracks the output

voltage. The voltage developed across C3 is sensed and regulated

via the resistor divider R1 and R3 connected to U1’s FB pin.

The values of R1 and R3 are selected such that, at the desired

output voltage, the voltage at the FB pin is 1.65 V.

Regulation is maintained by skipping switching cycles. As the

output voltage rises, the current into the FB pin will rise. If

this exceeds IFB then subsequent cycles will be skipped until the

current reduces below IFB. Thus, as the output load is reduced,

more cycles will be skipped and if the load increases, fewer

600

020

68 kHz

64 kHz

VDRAIN

Time (μs)

PI-3660-081303

500

400

300

200

100

2-5

LNK302/304-306

Rev. I 11/08

Figure 6a. Recommended Printed Circuit Layout for LinkSwitch-TN in a Buck Converter Conﬁ guration using P or G Package.

cycles are skipped. To provide overload protection if no cycles

are skipped during a 50 ms period, LinkSwitch-TN will enter

auto-restart (LNK304-306), limiting the average output power

to approximately 6% of the maximum overload power. Due to

tracking errors between the output voltage and the voltage across

C3 at light load or no load, a small pre-load may be required

(R4). For the design in Figure 5, if regulation to zero load is

required, then this value should be reduced to 2.4 kΩ.

Key Application Considerations

LinkSwitch-TN Design Considerations

Output Current Table

Data sheet maximum output current table (Table 1) represents

the maximum practical continuous output current for both

mostly discontinuous conduction mode (MDCM) and continuous

conduction mode (CCM) of operation that can be delivered from

a given LinkSwitch-TN device under the following assumed

conditions:

1) Buck converter topology.

2) The minimum DC input voltage is ≥70 V. The value of

input capacitance should be large enough to meet this

criterion.

3) For CCM operation a KRP* of 0.4.

4) Output voltage of 12 VDC.

5) Efﬁ ciency of 75%.

6) A catch/freewheeling diode with trr ≤75 ns is used for

MDCM operation and for CCM operation, a diode with

trr ≤35 ns is used.

7) The part is board mounted with SOURCE pins soldered

to a sufﬁ cient area of copper to keep the SOURCE pin

temperature at or below 100 °C.

*KRP is the ratio of ripple to peak inductor current.

LinkSwitch-TN Selection and Selection Between

MDCM and CCM Operation

Select the LinkSwitch-TN device, freewheeling diode and output

inductor that gives the lowest overall cost. In general, MDCM

PI-3750-121106

RF1 D3

C3C5C4

Optimize hatched copper areas ( ) for heatsinking and EMI.

LinkSwitch-TN

INPUT DC

OUTPUT

Figure 6b. Recommended Printed Circuit Layout for LinkSwitch-TN in a Buck Converter Conﬁ guration using D Package

to Bottom Side of the Board.

INPUT

OUTPUT

PI-4546-011807

Optimize hatched copper areas ( ) for heatsinking and EMI.

RF1 D3

C4 C5 C3

LinkSwitch-TN

2-6

Rev. I 11/08

LNK302/304-306

Table 2. Common Circuit Conﬁ gurations Using LinkSwitch-TN. (continued on next page)

TOPOLOGY BASIC CIRCUIT SCHEMATIC KEY FEATURES

High-Side

Buck –

Direct

Feedback

1. Output referenced to input

2. Positive output (VO) with respect to -VIN

3. Step down – VO < VIN

4. Low cost direct feedback (±10% typ.)

High-Side

Buck –

Optocoupler

Feedback

1. Output referenced to input

2. Positive output (VO) with respect to -VIN

3. Step down – VO < VIN

4. Optocoupler feedback

- Accuracy only limited by reference

choice

- Low cost non-safety rated opto

- No pre-load required

5. Minimum no-load consumption

Low-Side

Buck –

Optocoupler

Feedback

1. Output referenced to input

2. Negative output (VO) with respect to +VIN

3. Step down – VO < VIN

4. Optocoupler feedback

- Accuracy only limited by reference

choice

- Low cost non-safety rated opto

- No pre-load required

- Ideal for driving LEDs

Low-Side

Buck –

Constant

Current LED

Driver

High-Side

Buck Boost –

Direct

Feedback

1. Output referenced to input

2. Negative output (VO) with respect to +VIN

3. Step up/down – VO > VIN or VO < VIN

4. Low cost direct feedback (±10% typ.)

5. Fail-safe – output is not subjected to input

voltage if the internal MOSFET fails

6. Ideal for driving LEDs – better accuracy

and temperature stability than Low-side

Buck constant current LED driver

High-Side

Buck Boost –

Constant

Current LED

Driver

VIN

PI-3751-121003

FB BP

LinkSwitch-TN

PI-3752-121003

VIN

LinkSwitch-TN

PI-3753-111903

+ +

BP FB

VIN

LinkSwitch-TN

PI-3754-112103

BP FB

VIN

R =

VIN

PI-3755-121003

FB BP

LinkSwitch-TN

RSENSE =

RSENSE

300 Ω

2 kΩ

2 V

100 nF

10 μF

50 V

VIN

PI-3779-120803

FB BP

LinkSwitch-TN

2-7

LNK302/304-306

Rev. I 11/08

Table 2 (cont). Common Circuit Conﬁ gurations Using LinkSwitch-TN.

TOPOLOGY BASIC CIRCUIT SCHEMATIC KEY FEATURES

Low-Side

Buck Boost –

Optocoupler

Feedback

1. Output referenced to input

2. Positive output (VO) with respect to +VIN

3. Step up/down – VO > VIN or VO < VIN

4. Optocoupler feedback

- Accuracy only limited by reference

choice

- Low cost non-safety rated opto

- No pre-load required

5. Fail-safe – output is not subjected to input

voltage if the internal MOSFET fails

provides the lowest cost and highest efﬁ ciency converter. CCM

designs require a larger inductor and ultra-fast (trr ≤35 ns)

freewheeling diode in all cases. It is lower cost to use a larger

LinkSwitch-TN in MDCM than a smaller LinkSwitch-TN in CCM

because of the additional external component costs of a CCM

design. However, if the highest output current is required, CCM

should be employed following the guidelines below.

Topology Options

LinkSwitch-TN can be used in all common topologies, with or

without an optocoupler and reference to improve output voltage

tolerance and regulation. Table 2 provide a summary of these

conﬁ gurations. For more information see the Application

Note – LinkSwitch-TN Design Guide.

Component Selection

Referring to Figure 5, the following considerations may be

helpful in selecting components for a LinkSwitch-TN design.

Freewheeling Diode D1

Diode D1 should be an ultra-fast type. For MDCM, reverse

recovery time trr ≤75 ns should be used at a temperature of

70 °C or below. Slower diodes are not acceptable, as continuous

mode operation will always occur during startup, causing high

leading edge current spikes, terminating the switching cycle

prematurely, and preventing the output from reaching regulation.

If the ambient temperature is above 70 °C then a diode with

trr ≤35 ns should be used.

For CCM an ultra-fast diode with reverse recovery time

trr ≤35 ns should be used. A slower diode may cause excessive

leading edge current spikes, terminating the switching cycle

prematurely and preventing full power delivery.

Fast and slow diodes should never be used as the large reverse

recovery currents can cause excessive power dissipation in the

diode and/or exceed the maximum drain current speciﬁ cation

of LinkSwitch-TN.

Feedback Diode D2

Diode D2 can be a low-cost slow diode such as the 1N400X

series, however it should be speciﬁ ed as a glass passivated type

to guarantee a speciﬁ ed reverse recovery time. To a ﬁ rst order,

the forward drops of D1 and D2 should match.

Inductor L1

Choose any standard off-the-shelf inductor that meets the

design requirements. A “drum” or “dog bone” “I” core

inductor is recommended with a single ferrite element due to

its low cost and very low audible noise properties. The typical

inductance value and RMS current rating can be obtained from

the LinkSwitch-TN design spreadsheet available within the

PI Expert design suite from Power Integrations. Choose L1

greater than or equal to the typical calculated inductance with

RMS current rating greater than or equal to calculated RMS

inductor current.

Capacitor C2

The primary function of capacitor C2 is to smooth the inductor

current. The actual output ripple voltage is a function of this

capacitor’s ESR. To a ﬁ rst order, the ESR of this capacitor

should not exceed the rated ripple voltage divided by the typical

current limit of the chosen LinkSwitch-TN.

Feedback Resistors R1 and R3

The values of the resistors in the resistor divider formed by

R1 and R3 are selected to maintain 1.65 V at the FB pin. It is

recommended that R3 be chosen as a standard 1% resistor of

2 kΩ. This ensures good noise immunity by biasing the feedback

network with a current of approximately 0.8 mA.

Feedback Capacitor C3

Capacitor C3 can be a low cost general purpose capacitor. It

provides a “sample and hold” function, charging to the output

voltage during the off time of LinkSwitch-TN. Its value should

be 10 μF to 22 μF; smaller values cause poorer regulation at

light load conditions.

LinkSwitch-TN

PI-3756-111903

BP FB

VIN

2-8

Rev. I 11/08

LNK302/304-306

Pre-load Resistor R4

In high-side, direct feedback designs where the minimum load

is <3 mA, a pre-load resistor is required to maintain output

regulation. This ensures sufﬁ cient inductor energy to pull the

inductor side of the feedback capacitor C3 to input return via

D2. The value of R4 should be selected to give a minimum

output load of 3 mA.

In designs with an optocoupler the Zener or reference bias

current provides a 1 mA to 2 mA minimum load, preventing

“pulse bunching” and increased output ripple at zero load.

LinkSwitch-TN Layout Considerations

In the buck or buck-boost converter conﬁ guration, since the

SOURCE pins in LinkSwitch-TN are switching nodes, the copper

area connected to SOURCE should be minimized to minimize

EMI within the thermal constraints of the design.

In the boost conﬁ guration, since the SOURCE pins are tied

to DC return, the copper area connected to SOURCE can be

maximized to improve heatsinking.

The loop formed between the LinkSwitch-TN, inductor (L1),

freewheeling diode (D1), and output capacitor (C2) should

be kept as small as possible. The BYPASS pin capacitor

C1 (Figure 6) should be located physically close to the

SOURCE (S) and BYPASS (BP) pins. To minimize direct

coupling from switching nodes, the LinkSwitch-TN should be

placed away from AC input lines. It may be advantageous to

place capacitors C4 and C5 in-between LinkSwitch-TN and the

AC input. The second rectiﬁ er diode D4 is optional, but may

be included for better EMI performance and higher line surge

withstand capability.

Quick Design Checklist

As with any power supply design, all LinkSwitch-TN designs

should be veriﬁ ed for proper functionality on the bench. The

following minimum tests are recommended:

1) Adequate DC rail voltage – check that the minimum DC

input voltage does not fall below 70 VDC at maximum load,

minimum input voltage.

2) Correct Diode Selection – UF400x series diodes are

recommended only for designs that operate in MDCM at

an ambient of 70 °C or below. For designs operating in

continuous conduction mode (CCM) and/or higher ambients,

then a diode with a reverse recovery time of 35 ns or better,

such as the BYV26C, is recommended.

3) Maximum drain current – verify that the peak drain current

is below the data sheet peak drain speciﬁ cation under

worst-case conditions of highest line voltage, maximum

overload (just prior to auto-restart) and highest ambient

temperature.

4) Thermal check – at maximum output power, minimum

input voltage and maximum ambient temperature, verify

that the LinkSwitch-TN SOURCE pin temperature is

100 °C or below. This ﬁ gure ensures adequate margin due

to variations in RDS(ON) from part to part. A battery powered

thermocouple meter is recommended to make measurements

when the SOURCE pins are a switching node. Alternatively,

the ambient temperature may be raised to indicate margin

to thermal shutdown.

In a LinkSwitch-TN design using a buck or buck boost converter

topology, the SOURCE pin is a switching node. Oscilloscope

measurements should therefore be made with probe grounded

to a DC voltage, such as primary return or DC input rail, and

not to the SOURCE pins. The power supply input must always

be supplied from an isolated source (e.g. via an isolation

transformer).

2-9

LNK302/304-306

Rev. I 11/08

ABSOLUTE MAXIMUM RATINGS(1,5)

DRAIN Voltage .................................. ................ -0.3 V to 700 V

Peak DRAIN Current (LNK302).................200 mA (375 mA)(2)

Peak DRAIN Current (LNK304).................400 mA (750 mA)(2)

Peak DRAIN Current (LNK305).................800 mA (1500 mA)(2)

Peak DRAIN Current (LNK306).................1400 mA (2600 mA)(2)

FEEDBACK Voltage .........................................-0.3 V to 9 V

FEEDBACK Current.............................................100 mA

BYPASS Voltage ..........................................-0.3 V to 9 V

Storage Temperature .......................................... -65 °C to 150 °C

Operating Junction Temperature(3) ..................... -40 °C to 150 °C

Lead Temperature(4) ........................................................260 °C

Notes:

1. All voltages referenced to SOURCE, TA = 25 °C.

2. The higher peak DRAIN current is allowed if the DRAIN

to SOURCE voltage does not exceed 400 V.

3. Normally limited by internal circuitry.

4. 1/16 in. from case for 5 seconds.

5. Maximum ratings speciﬁ ed may be applied, one at a time,

without causing permanent damage to the product.

Exposure to Absolute Maximum Rating conditions for

extended periods of time may affect product reliability.

THERMAL IMPEDANCE

Thermal Impedance: P or G Package:

(θJA) ........................... 70 °C/W(3); 60 °C/W(4)

(θJC)(1) ............................................... 11 °C/W

D Package:

(θJA) ..................... .... 100 °C/W(3); 80 °C/W(4)

(θJC)(2) ............................................... 30 °C/W

Notes:

1. Measured on pin 2 (SOURCE) close to plastic interface.

2. Measured on pin 8 (SOURCE) close to plastic interface.

3. Soldered to 0.36 sq. in. (232 mm2), 2 oz. (610 g/m2) copper clad.

4. Soldered to 1 sq. in. (645 mm2), 2 oz. (610 g/m2) copper clad.

Parameter Symbol

Conditions

SOURCE = 0 V; TJ = -40 to 125 °C

See Figure 7

(Unless Otherwise Speciﬁ ed)

Min Typ Max Units

CONTROL FUNCTIONS

Output

Frequency fOSC TJ = 25 °C Average 62 66 70 kHz

Peak-Peak Jitter 4

Maximum Duty

Cycle DCMAX S2 Open 66 69 72 %

FEEDBACK Pin

Turnoff Threshold

Current

IFB TJ = 25 °C 30 49 68 μA

FEEDBACK Pin

Voltage at Turnoff

Threshold

VFB 1.54 1.65 1.76 V

DRAIN Supply

Current

IS1

VFB ≥2 V

(MOSFET Not Switching)

See Note A

160 220 μA

IS2

FEEDBACK

Open

(MOSFET

Switching)

See Notes A, B

LNK302/304 200 260

μA

LNK305 220 280

LNK306 250 310

2-10

Rev. I 11/08

LNK302/304-306

Parameter Symbol

Conditions

SOURCE = 0 V; TJ = -40 to 125 °C

See Figure 7

(Unless Otherwise Speciﬁ ed)

Min Typ Max Units

CONTROL FUNCTIONS (cont.)

BYPASS Pin

Charge Current

ICH1

VBP = 0 V

TJ = 25 °C

LNK302/304 -5.5 -3.3 -1.8

LNK305/306 -7.5 -4.6 -2.5

ICH2

VBP = 4 V

TJ = 25 °C

LNK302/304 -3.8 -2.3 -1.0

LNK305/306 -4.5 -3.3 -1.5

BYPASS Pin

Voltage VBP 5.55 5.8 6.10 V

BYPASS Pin

Voltage Hysteresis VBPH 0.8 0.95 1.2 V

BYPASS Pin

Supply Current IBPSC See Note D 68 μA

CIRCUIT PROTECTION

Current Limit ILIMIT (See

Note E)

di/dt = 55 mA/μs

TJ = 25 °C

LNK302

126 136 146

di/dt = 250 mA/μs

TJ = 25 °C145 165 185

di/dt = 65 mA/μs

TJ = 25 °C

LNK304

240 257 275

di/dt = 415 mA/μs

TJ = 25 °C271 308 345

di/dt = 75 mA/μs

TJ = 25 °C

LNK305

350 375 401

di/dt = 500 mA/μs

TJ = 25 °C396 450 504

di/dt = 95 mA/μs

TJ = 25 °C

LNK306

450 482 515

di/dt = 610 mA/μs

TJ = 25 °C508 578 647

Minimum On Time tON(MIN)

LNK302/304 280 360 475

LNK305 360 460 610

LNK306 400 500 675

Leading Edge

Blanking Time tLEB

TJ = 25 °C

See Note F 170 215 ns

Thermal Shutdown

Temperature TSD 135 142 150 °C

2-11

LNK302/304-306

Rev. I 11/08

Parameter Symbol

Conditions

SOURCE = 0 V; TJ = -40 to 125 °C

See Figure 7

(Unless Otherwise Speciﬁ ed)

Min Typ Max Units

CIRCUIT PROTECTION (cont.)

Thermal Shutdown

Hysteresis TSHD See Note G 75 °C

OUTPUT

ON-State

Resistance RDS(ON)

LNK302

ID = 13 mA

TJ = 25 °C48 55.2

TJ = 100 °C76 88.4

LNK304

ID = 25 mA

TJ = 25 °C24 27.6

TJ = 100 °C38 44.2

LNK305

ID = 35 mA

TJ = 25 °C12 13.8

TJ = 100 °C19 22.1

LNK306

ID = 45 mA

TJ = 25 °C7 8.1

TJ = 100 °C11 12.9

OFF-State Drain

Leakage Current IDSS

VBP = 6.2 V, VFB ≥2 V,

VDS = 560 V,

TJ = 25 °C

LNK302/304 50

μA

LNK305 70

LNK306 90

Breakdown Voltage BVDSS

VBP = 6.2 V, VFB ≥2 V,

TJ = 25 °C700 V

Rise Time tRMeasured in a Typical Buck

Converter Application

50 ns

Fall Time tF50 ns

DRAIN Supply

Voltage 50 V

Output Enable

Delay tEN See Figure 9 10 μs

Output Disable

Setup Time tDST 0.5 μs

Auto-Restart

ON-Time tAR

TJ = 25 °C

See Note H

LNK302 ms

LNK304-306 50

Auto-Restart

Duty Cycle DCAR

LNK302 %

LNK304-306 6

Not Applicable

2-12

Rev. I 11/08

LNK302/304-306

NOTES:

A. Total current consumption is the sum of IS1 and IDSS when FEEDBACK pin voltage is ≥2 V (MOSFET not

switching) and the sum of IS2 and IDSS when FEEDBACK pin is shorted to SOURCE (MOSFET switching).

B Since the output MOSFET is switching, it is difﬁ cult to isolate the switching current from the supply current at the

DRAIN. An alternative is to measure the BYPASS pin current at 6 V.

C. See Typical Performance Characteristics section Figure 14 for BYPASS pin start-up charging waveform.

D. This current is only intended to supply an optional optocoupler connected between the BYPASS and FEEDBACK

pins and not any other external circuitry.

E. For current limit at other di/dt values, refer to Figure 13.

F. This parameter is guaranteed by design.

G. This parameter is derived from characterization.

H. Auto-restart on time has the same temperature characteristics as the oscillator (inversely proportional to

frequency).

Figure 7. LinkSwitch-TN General Test Circuit.

PI-3490-060204

50 V50 V

DFB

470 kΩ

0.1 μF

470 Ω

5 W

PI-3707-112503

tEN

MAX

tP = 1

fOSC

DRAIN

(internal signal)

Figure 8. LinkSwitch-TN Duty Cycle Measurement. Figure 9. LinkSwitch-TN Output Enable Timing.

2-13

LNK302/304-306

Rev. I 11/08

200

300

350

400

250

04286 101214161820

DRAIN Voltage (V)

DRAIN Current (mA)

PI-3661-071404

150

100

Scaling Factors:

LNK302 0.5

LNK304 1.0

LNK305 2.0

LNK306 3.4

25 °C

100 °C

Typical Performance Characteristics

Figure 14. BYPASS Pin Start-up Waveform.

1.1

1.0

0.9

-50 -25 0 25 50 75 100 125 150

Junction Temperature (°C)

Breakdown Voltage

(Normalized to 25 °C)

PI-2213-012301

00.2 0.4 0.6 0.8 1.0

Time (ms)

PI-2240-012301

BYPASS Pin Voltage (V)

Figure 10. Breakdown vs. Temperature.

Figure 12. Current Limit vs. Temperature at

Normalized di/dt.

Figure 13. Current Limit vs. di/dt.

Figure 15. Output Characteristics.

1.2

1.0

0.8

0.6

0.4

0.2

-50 -25 0 25 50 75 100 125

Junction Temperature (°C)

PI-2680-012301

Output Frequency

(Normalized to 25 °C)

Figure 11. Frequency vs. Temperature.

Normalized di/dt

PI-3710-071204

Normalized Current Limit

1.0

1.2

1.4

0.8

0.6

0.4

0.2

123456

LNK302

LNK304

LNK305

LNK306

Normalized

di/dt = 1

55 mA/μs

65 mA/μs

75 mA/μs

95 mA/μs

Normalized

Current

Limit = 1

136 mA

257 mA

375 mA

482 mA

Temperature (°C)

PI-3709-111203

Current Limit

(Normalized to 25 °C)

1.0

1.2

1.4

0.8

0.6

0.4

0.2

-50 0 50 100 150

di/dt = 1

di/dt = 6

Normalized di/dt

2-14

Rev. I 11/08

LNK302/304-306

Figure 16. COSS vs. Drain Voltage.

Drain Voltage (V)

Drain Capacitance (pF)

PI-3711-071404

0 100 200 300 400 500 600

100

1000

LNK302 0.5

LNK304 1.0

LNK305 2.0

LNK306 3.4

Scaling Factors:

Typical Performance Characteristics (cont.)

PART ORDERING INFORMATION

LinkSwitch Product Family

TN Series Number

Package Identiﬁ er

G Plastic Surface Mount DIP

P Plastic DIP

D Plastic SO-8C

Lead Finish

N Pure Matte Tin (RoHS Compliant)

G RoHS Compliant and Halogen Free (D package only)

Tape & Reel and Other Options

Blank Standard Conﬁ gurations

TL Tape & Reel, 1 k pcs minimum for G Package. 2.5 k pcs

for D Package. Not available for P Package.

LNK 304 G N - TL

2-15

LNK302/304-306

Rev. I 11/08

Notes:

1. Package dimensions conform to JEDEC specification

MS-001-AB (Issue B 7/85) for standard dual-in-line (DIP)

package with .300 inch row spacing.

2. Controlling dimensions are inches. Millimeter sizes are

shown in parentheses.

3. Dimensions shown do not include mold flash or other

protrusions. Mold flash or protrusions shall not exceed

.006 (.15) on any side.

4. Pin locations start with Pin 1, and continue counter-clock-

wise to Pin 8 when viewed from the top. The notch and/or

dimple are aids in locating Pin 1. Pin 6 is omitted.

5. Minimum metal to metal spacing at the package body for

the omitted lead location is .137 inch (3.48 mm).

6. Lead width measured at package body.

7. Lead spacing measured with the leads constrained to be

perpendicular to plane T.

.008 (.20)

.015 (.38)

.300 (7.62) BSC

(NOTE 7)

.300 (7.62)

.390 (9.91)

.367 (9.32)

.387 (9.83)

.240 (6.10)

.260 (6.60)

.125 (3.18)

.145 (3.68)

.057 (1.45)

.068 (1.73)

.120 (3.05)

.140 (3.56)

.015 (.38)

MINIMUM

.048 (1.22)

.053 (1.35)

.100 (2.54) BSC

.014 (.36)

.022 (.56)

-E-

Pin 1

SEATING

PLANE

-D-

-T-

P08B

DIP-8B

PI-2551-121504

D S .004 (.10)

⊕

T E D S .010 (.25) M

⊕

(NOTE 6)

.137 (3.48)

MINIMUM

SMD-8B

PI-2546-121504

.004 (.10)

.012 (.30)

.036 (0.91)

.044 (1.12)

.004 (.10)

0 -

° 8°

.367 (9.32)

.387 (9.83)

.048 (1.22) .009 (.23)

.053 (1.35)

.032 (.81)

.037 (.94)

.125 (3.18)

.145 (3.68)

-D-

Notes:

1. Controlling dimensions are

inches. Millimeter sizes are

shown in parentheses.

2. Dimensions shown do not

include mold flash or other

protrusions. Mold flash or

protrusions shall not exceed

.006 (.15) on any side.

3. Pin locations start with Pin 1,

and continue counter-clock-

wise to Pin 8 when viewed

from the top. Pin 6 is omitted.

4. Minimum metal to metal

spacing at the package body

for the omitted lead location

is .137 inch (3.48 mm).

5. Lead width measured at

package body.

6. D and E are referenced

datums on the package

body.

.057 (1.45)

.068 (1.73)

(NOTE 5)

E S

.100 (2.54) (BSC)

.372 (9.45)

.240 (6.10) .388 (9.86)

.137 (3.48)

MINIMUM

.260 (6.60) .010 (.25)

-E-

Pin 1

D S .004 (.10)

⊕

G08B

.420

.046 .060 .060 .046

.080

Pin 1

.086

.186

.286

Solder Pad Dimensions

2-16

Rev. I 11/08

LNK302/304-306

PI-4526-040207

D07C

SO-8C

3.90 (0.154) BSC

Notes:

1. JEDEC reference: MS-012.

2. Package outline exclusive of mold flash and metal burr.

3. Package outline inclusive of plating thickness.

4. Datums A and B to be determined at datum plane H.

5. Controlling dimensions are in millimeters. Inch dimensions

are shown in parenthesis. Angles in degrees.

0.20 (0.008) C

1 4

26.00 (0.236) BSC

4.90 (0.193) BSC

0.10 (0.004) C

0.10 (0.004) C 2X

A-B

1.27 (0.050) BSC

7X 0.31 - 0.51 (0.012 - 0.020)

0.25 (0.010) M C A-B D

0.25 (0.010)

0.10 (0.004)

(0.049 - 0.065)

1.25 - 1.65

1.75 (0.069)

1.35 (0.053)

0.10 (0.004) C

1.27 (0.050)

0.40 (0.016)

GAUGE

PLANE

0 - 8

1.04 (0.041) REF 0.25 (0.010)

BSC

SEATING

PLANE

0.25 (0.010)

0.17 (0.007)

DETAIL A

SEATING PLANE

Pin 1 ID

+ +

4.90 (0.193)

1.27 (0.050) 0.60 (0.024)

2.00 (0.079)

Reference

Solder Pad

Dimensions

2-17

LNK302/304-306

Rev. I 11/08

Notes

2-18

Rev. I 11/08

LNK302/304-306

Notes

2-19

LNK302/304-306

Rev. I 11/08

Revision Notes Date

C 1) Released ﬁ nal data sheet. 3/03

D 1) Corrected Minimum On Time. 1/04

E 1) Added LNK302. 8/04

F 1) Added lead-free ordering information. 12/04

G 1) Minor error corrections.

2) Renamed Feedback Pin Voltage parameter to Feedback Pin Voltage at Turnoff Threshold and

removed condition.

3/05

H 1) Added SO-8C package. 12/06

I 1) Updated Part Ordering Information section with Halogen Free 11/08

2-20

Rev. I 11/08

LNK302/304-306

For the latest updates, visit our website: www.powerint.com

Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability. Power

Integrations does not assume any liability arising from the use of any device or circuit described herein. POWER INTEGRATIONS MAKES

NO WARRANTY HEREIN AND SPECIFICALLY DISCLAIMS ALL WARRANTIES INCLUDING, WITHOUT LIMITATION, THE IMPLIED

WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT OF THIRD PARTY RIGHTS.

Patent Information

The products and applications illustrated herein (including transformer construction and circuits external to the products) may be covered

by one or more U.S. and foreign patents, or potentially by pending U.S. and foreign patent applications assigned to Power Integrations. A

complete list of Power Integrations patents may be found at www.powerint.com. Power Integrations grants its customers a license under

certain patent rights as set forth at http://www.powerint.com/ip.htm.

Life Support Policy

POWER INTEGRATIONS PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR

SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF POWER INTEGRATIONS. As used herein:

A Life support device or system is one which, (i) is intended for surgical implant into the body, or (ii) supports or sustains life, and (iii)

whose failure to perform, when properly used in accordance with instructions for use, can be reasonably expected to result in signiﬁ cant

injury or death to the user.

A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause

the failure of the life support device or system, or to affect its safety or effectiveness.

The PI logo, TOPSwitch, TinySwitch, LinkSwitch, DPA-Switch, PeakSwitch, EcoSmart, Clampless, E-Shield, Filterfuse, StakFET, PI Expert

and PI FACTS are trademarks of Power Integrations, Inc. Other trademarks are property of their respective companies.

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