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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 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 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

EcoSmart

– 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, 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 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

OUTPUT CURRENT TABLE

PRODUCT

230 VAC ±15% 85-265 VAC

MDCM

CCM

MDCM

CCM

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

Output

Wide Range

HV DC Input

PI-3492-111903

LinkSwitch-TN

Summary of content (16 pages)

PAGE 1
LNK302/304-306 ® LinkSwitch-TN Family Lowest Component Count, Energy Efﬁcient Off-Line Switcher IC 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 inducto
PAGE 2
LNK302/304-306 BYPASS (BP) DRAIN (D) REGULATOR 5.8 V BYPASS PIN UNDER-VOLTAGE + 5.8 V 4.85 V - CURRENT LIMIT COMPARATOR 6.3 V + VI - LIMIT JITTER CLOCK DCMAX THERMAL SHUTDOWN OSCILLATOR FEEDBACK (FB) 1.65 V -VT S Q R Q LEADING EDGE BLANKING SOURCE (S) PI-3904-020805 Figure 2a. Functional Block Diagram (LNK302). BYPASS (BP) DRAIN (D) REGULATOR 5.8 V FAULT PRESENT AUTORESTART COUNTER CLOCK RESET + 5.8 V 4.85 V BYPASS PIN UNDER-VOLTAGE - CURRENT LIMIT COMPARATOR 6.
PAGE 3
LNK302/304-306 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.
PAGE 4
LNK302/304-306 PI-3660-081303 600 500 VDRAIN 400 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. 300 The input stage comprises fusible resistor RF1, diodes D3 and D4, capacitors C4 and C5, and inductor L2.
PAGE 5
LNK302/304-306 LinkSwitch-TN RF1 D1 L2 D FB AC INPUT C4 C5 S S S S C1 R3 + L1 C3 C2 DC OUTPUT D1 D4 Optimize hatched copper areas ( D2 R1 BP ) for heatsinking and EMI. PI-3750-083004 Figure 6. Recommended Printed Circuit Layout for LinkSwitch-TN in a Buck Converter Conﬁguration. cycles are skipped.
PAGE 6
LNK302/304-306 TOPOLOGY BASIC CIRCUIT SCHEMATIC High-Side Buck – Direct Feedback FB BP S D + KEY FEATURES + LinkSwitch-TN VIN 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.
PAGE 7
LNK302/304-306 TOPOLOGY Low-Side Buck Boost – Optocoupler Feedback BASIC CIRCUIT SCHEMATIC KEY FEATURES + LinkSwitch-TN VO VIN BP S FB D + PI-3756-111903 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 Table 2 (cont).
PAGE 8
LNK302/304-306 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 veriﬁed 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.
PAGE 9
LNK302/304-306 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...........................................
PAGE 10
LNK302/304-306 Conditions Parameter Symbol SOURCE = 0 V; TJ = -40 to 125 °C See Figure 7 (Unless Otherwise Speciﬁed) 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 mA BYPASS Pin Voltage VBP 5.55 5.8 6.10 V BYPASS Pin Voltage Hysteresis VBPH 0.8 0.95 1.
PAGE 11
LNK302/304-306 Conditions Parameter Symbol SOURCE = 0 V; TJ = -40 to 125 °C See Figure 7 (Unless Otherwise Speciﬁed) Min Typ 170 215 135 142 Max Units CIRCUIT PROTECTION (cont.
PAGE 12
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 difﬁcult 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.
PAGE 13
LNK302/304-306 Typical Performance Characteristics 1.0 0.9 -50 -25 0 25 50 PI-2680-012301 1.2 Output Frequency (Normalized to 25 °C) PI-2213-012301 1.0 0.8 0.6 0.4 0.2 0 75 100 125 150 -50 -25 Junction Temperature (°C) 0.8 Normalized di/dt di/dt = 1 di/dt = 6 0.4 0.2 0 -50 PI-3710-071204 1.2 1.0 0.8 0.6 LNK302 LNK304 LNK305 LNK306 0.4 0.
PAGE 14
LNK302/304-306 Typical Performance Characteristics (cont.) PI-3711-071404 Drain Capacitance (pF) 1000 100 Scaling Factors: LNK302 0.5 LNK304 1.0 LNK305 2.0 LNK306 3.4 10 1 0 100 200 300 400 500 600 Drain Voltage (V) Figure 16. COSS vs. Drain Voltage.
PAGE 15
LNK302/304-306 DIP-8B ⊕ D S .004 (.10) -E- 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.
PAGE 16
LNK302/304-306 Revision Notes Date C 1) Released Final 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 For the latest updates, visit our website: www.powerint.