Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsPMICsPMIC - AC/DC converter, offline switcher Flyback, Forward Frequency control, Soft Star

VOUT

VIN

OUT

FEEDBACK

WITH

ISOLATION

COMP GND

VCC

LM5021

90 ~ 264 Vac

LM5021

www.ti.com

SNVS359D –MAY 2005–REVISED MARCH 2013

LM5021 AC-DC Current Mode PWM Controller

Check for Samples: LM5021

FEATURES

DESCRIPTION

The LM5021 off-line pulse width modulation (PWM)

• Ultra Low Start-up Current (25 µA maximum)

controller contains all of the features needed to

• Current Mode Control

implement highly efficient off-line single-ended

• Skip Cycle Mode for Low Standby Power

flyback and forward power converters using current-

mode control. The LM5021 features include an ultra-

• Single Resistor Programmable Oscillator

low (25 µA) start-up current, which minimizes power

• Synchronizable Oscillator

losses in the high voltage start-up network. A skip

• Adjustable Soft-Start

cycle mode reduces power consumption with light

loads for energy conserving applications (ENERGY

• Integrated 0.7A Peak Gate Driver

STAR®, CECP, etc.). Additional features include

• Direct Opto-Coupler Interface

under-voltage lockout, cycle-by-cycle current limit,

• Maximum Duty Cycle Limiting (80% for

hiccup mode overload protection, slope com-

LM5021-1 or 50% for LM5021-2)

pensation, soft-start and oscillator synchronization

capability. This high performance 8-pin IC has total

• Slope Compensation for (LM5021-1 Only)

propagation delays less than 100nS and a 1MHz

• Under Voltage Lockout (UVLO) with Hysteresis

capable oscillator that is programmed with a single

• Cycle-by-Cycle Over-Current Protection

resistor.

• Hiccup Mode for Continuous Overload

WHITE SPACE

Protection

• Leading Edge Blanking of Current Sense

Signal

• Packages: VSSOP-8 or PDIP-8

Simplified Application Diagram

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2All trademarks are the property of their respective owners.

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

Summary of content (23 pages)

PAGE 1
LM5021 www.ti.com SNVS359D – MAY 2005 – REVISED MARCH 2013 LM5021 AC-DC Current Mode PWM Controller Check for Samples: LM5021 FEATURES DESCRIPTION • • • • • • • • • The LM5021 off-line pulse width modulation (PWM) controller contains all of the features needed to implement highly efficient off-line single-ended flyback and forward power converters using currentmode control.
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LM5021 SNVS359D – MAY 2005 – REVISED MARCH 2013 www.ti.com Connection Diagram COMP 1 8 SS VIN 2 7 RT VCC 3 6 CS OUT 4 5 GND Figure 1. Top View VSSOP-8 (See Package Number DGK0008A) PDIP-8 (See Package Number P0008E) PIN DESCRIPTIONS Pin Name Description Application Information 1 COMP Control input for the Pulse Width Modulator and Hiccup comparators. COMP pull-up is provided by an internal 5K resistor which may be used to bias an opto-coupler transistor. 2 VIN Input voltage.
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LM5021 www.ti.com SNVS359D – MAY 2005 – REVISED MARCH 2013 Absolute Maximum Ratings (1) (2) VIN to GND -0.3V to 30V VIN Clamp Continuous Current 5mA CS to GND -0.3V to 1.25V RT to GND -0.3V to 5.5V All other pins to GND -0.3V to 7.0V ESD Rating (3) Human Body Model 2kV Storage Temperature -65°C to +150°C Operating Junction Temperature (1) (2) (3) +150°C Absolute Maximum Ratings are limits beyond which damage to the device may occur.
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LM5021 SNVS359D – MAY 2005 – REVISED MARCH 2013 www.ti.com Electrical Characteristics(1) (continued) Specifications in standard type face are for TJ= +25°C and those in boldface type apply over the full Operating Junction Temperature Range. Unless otherwise specified: VIN = 15V, RT = 44.2KΩ. Symbol Parameter Conditions Min Typ Max Unit SS pin open-circuit voltage 4.3 5.2 6.1 V Soft-start Current Source 15 22 30 µA 0.35 0.55 0.
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LM5021 www.ti.com SNVS359D – MAY 2005 – REVISED MARCH 2013 Simplified Block Diagram 8.5V LINEAR REGULATOR VIN 2 VIN UVLO 20V RISING 7.25V FALLING 36V CLAMP VCC 3 VCC UVLO 7V RISING 5.8V FALLING EN VCC_UVLO DIS CLK VCC_UVLO RT/ SYNC 7 OSC VCC_UVLO SLOPE COMPENSATION RAMP GENERATOR (LM5021 - 1 ONLY) MAX DUTY LIMIT LM5021 - 1 (80%) LM5021 - 2 (50%) 50 PA 0 PA PWM COMPARATOR 5.2V 5k COMP 1 S DRIVER Q OUT 4 R + 1.25V 2R PWM LOGIC - R SKIP CYCLE COMPARATOR 550 mV 5.
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LM5021 SNVS359D – MAY 2005 – REVISED MARCH 2013 www.ti.com Typical Performance Characteristics Unless otherwise specified: TJ = 25°C. VIN Start-Up Current VIN UVLO 16 3 VIN Falling 12 VIN CURRENT (mA) VIN CURRENT (PA) 14 10 8 6 4 2 1 VIN Rising 2 0 15 0 16 17 19 18 20 0 21 10 20 VIN VOLTAGE (V) VIN (V) Figure 2. Figure 3.
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LM5021 www.ti.com SNVS359D – MAY 2005 – REVISED MARCH 2013 Typical Performance Characteristics (continued) Unless otherwise specified: TJ = 25°C. Output Switching Frequency vs RT OUT SWITCHING FREQUENCY (kHz) 1000 LM5021-1 LM5021-2 100 10 1 10 100 1000 RT (kQ) Figure 8.
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LM5021 SNVS359D – MAY 2005 – REVISED MARCH 2013 www.ti.com DETAILED OPERATING DESCRIPTION START UP CIRCUIT Referring to Figure 9, the input capacitor CVIN is trickle charged through the start-up resistor Rstart, when the rectified ac input voltage HV is applied. The VIN current consumed by the LM5021 is only 18 µA (nominal) while the capacitor CVIN is initially charged to the start-up threshold.
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LM5021 www.ti.com SNVS359D – MAY 2005 – REVISED MARCH 2013 VIN = 20V - 8.5V x CVCC CVIN (3) Assuming CVIN value as 10 µF, and CVCC of 1µF, then the drop in VIN will be 0.85V, or the VIN value drops to 19.15V. The value of the VCC capacitor can be small (less than 1uF) as it supplies only transient gate drive current of a short duration.
PAGE 10
LM5021 SNVS359D – MAY 2005 – REVISED MARCH 2013 www.ti.com The LM5021 CS comparator is very fast, and may respond to short duration noise pulses. Layout considerations are critical for the current sense filter and sense resistor. The capacitor associated with the CS filter must be placed very close to the device and connected directly to the pins of the IC (CS and GND).
PAGE 11
LM5021 www.ti.com SNVS359D – MAY 2005 – REVISED MARCH 2013 Figure 10, Figure 11, and Figure 12 illustrate the equivalent circuit of the hiccup mode for LM5021 and the relevant waveforms. During start-up and in normal operation, the external soft-start capacitor Css is pulled up by a current source that delivers 22 µA to the SS pin capacitor. In normal operation, the soft-start capacitor continues to charge and eventually reaches the saturation voltage of the current source (VSS_OCV, nominally 5.2V).
PAGE 12
LM5021 SNVS359D – MAY 2005 – REVISED MARCH 2013 www.ti.com 5.2V COMP OVERLOAD DETECTION 550 mV 5.2V + 4.6V - EN 22 PA + SS EN S + 4.6V 10 PA EN Q 0.25 PA R HICCUP MODE COMPARATOR 0.3V OUT DRIVER PWM + - RESTART COMPARATOR Figure 10. Hiccup Mode Control WHITE SPACE WHITE SPACE Soft-Start Normal operation Overload Detection SMPS latched OFF Soft-Start COMP -10 PA 5.2V 4.6V SS +22 PA -0.25 PA +22 PA 0.3V Figure 11.
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LM5021 www.ti.com SNVS359D – MAY 2005 – REVISED MARCH 2013 COMP 5.2V 4.6V SS -10 PA +22 PA during over +22 PA after releasing the over load load Figure 12. Waveform at SS and COMP Pin due to Brief Overload SKIP CYCLE OPERATION During light load conditions, the efficiency of the switching power supply typically drops as the losses associated with switching and operating bias currents of the converter become a significant percentage of the power delivered to the load.
PAGE 14
LM5021 SNVS359D – MAY 2005 – REVISED MARCH 2013 www.ti.com 5.2V 5k COMP 1.25V + PWM COMPARATOR 2R PWM LOGIC - R + SKIP CYCLE COMPARATOR 125 mV CS 1.8k + CLK LEADING EDGE BLANKING - CURRENT LIMIT COMPARATOR 500 mV Figure 13. Skip Cycle Control VIN OUT LM5021 Voffset > 125 mV CS VCC RSense Figure 14.
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LM5021 www.ti.
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LM5021 SNVS359D – MAY 2005 – REVISED MARCH 2013 www.ti.com REVISION HISTORY Changes from Revision C (March 2013) to Revision D • 16 Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM5021MM-1/NOPB VSSOP DGK 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1 LM5021MM-2 VSSOP DGK 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.0 Q1 LM5021MM-2/NOPB VSSOP DGK 8 1000 178.0 12.4 5.3 3.4 1.4 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 11-Oct-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM5021MM-1/NOPB VSSOP DGK 8 1000 210.0 185.0 35.0 LM5021MM-2 VSSOP DGK 8 1000 210.0 185.0 35.0 LM5021MM-2/NOPB VSSOP DGK 8 1000 210.0 185.0 35.0 LM5021MMX-1/NOPB VSSOP DGK 8 3500 367.0 367.0 35.0 LM5021MMX-2 VSSOP DGK 8 3500 367.0 367.0 35.0 LM5021MMX-2/NOPB VSSOP DGK 8 3500 367.0 367.0 35.
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