Texas Instruments AN-1907 LM3423 Скачать руководство пользователя страница 17

IMPORTANT NOTICE

Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other
changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest
issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and
complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale
supplied at the time of order acknowledgment.

TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms
and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary
to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily
performed.

TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and
applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide
adequate design and operating safeguards.

TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or
other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information
published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or
endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the
third party, or a license from TI under the patents or other intellectual property of TI.

Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration
and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered
documentation. Information of third parties may be subject to additional restrictions.

Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service
voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.
TI is not responsible or liable for any such statements.

Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements
concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support
that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which
anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause
harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use
of any TI components in safety-critical applications.

In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to
help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and
requirements. Nonetheless, such components are subject to these terms.

No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties
have executed a special agreement specifically governing such use.

Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in
military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components
which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and
regulatory requirements in connection with such use.

TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of
non-designated products, TI will not be responsible for any failure to meet ISO/TS16949.

Products

Applications

Audio

www.ti.com/audio

Automotive and Transportation

www.ti.com/automotive

Amplifiers

amplifier.ti.com

Communications and Telecom

www.ti.com/communications

Data Converters

dataconverter.ti.com

Computers and Peripherals

www.ti.com/computers

DLP® Products

www.dlp.com

Consumer Electronics

www.ti.com/consumer-apps

DSP

dsp.ti.com

Energy and Lighting

www.ti.com/energy

Clocks and Timers

www.ti.com/clocks

Industrial

www.ti.com/industrial

Interface

interface.ti.com

Medical

www.ti.com/medical

Logic

logic.ti.com

Security

www.ti.com/security

Power Mgmt

power.ti.com

Space, Avionics and Defense

www.ti.com/space-avionics-defense

Microcontrollers

microcontroller.ti.com

Video and Imaging

www.ti.com/video

RFID

www.ti-rfid.com

OMAP Applications Processors

www.ti.com/omap

TI E2E Community

e2e.ti.com

Wireless Connectivity

www.ti.com/wirelessconnectivity

Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265

Copyright © 2013, Texas Instruments Incorporated

Содержание AN-1907 LM3423

Страница 1: ...ation while providing inherent input voltage feed forward compensation The LM3423 includes a high voltage start up regulator that operates over a wide input range of 4 5V to 75V The PWM controller is designed for high speed capability including a switching frequency range to 2 0 MHz Additional features include zero current shutdown error amplifier precision reference logic compatible DIM input sui...

Страница 2: ...the use of on board jumpers refer to Table 2 Table 2 LM3423 Evaluation Board Jumpers Jumper Designation Function or Use Notes J1 Enable EN OPEN Disables LM3423 CLOSED Enables LM3423 J2 Current Limit IS OPEN Disables MOSFET RDS ON current sensing Q5 CLOSED Enables MOSFET RDS ON current sensing Q5 J3 Current Limit IS OPEN Disables external sense resistor MOSFET current sensing Q5 CLOSED Enables exte...

Страница 3: ...Top View LM3423 Pin Connection 5 Board Features This evaluation board has all the necessary connections and jumpers to evaluate the LM3423 controller in a boost converter topology with the following operating features and options 5 1 Setting Average LED Current The LM3423 uses peak current mode control to regulate the boosted output voltage An external current sense resistor RSENSE i e R9 in serie...

Страница 4: ... to understanding the relationship between VCSH and VSNS because VSNS and RSNS set the LED current The high side amplifier in forces its input terminals to equal potential Because of this the VSNS voltage is forced across RHSP Another way to view this is that the amplifier s output transistor pulls current through R7 RHSP until VHSP VHSN and this happens when the voltage across R7 is equal to VSNS...

Страница 5: ...n so that the current ripple ΔiL is between 20 and 40 of the average current IL through the inductor Figure 3 Inductor Current Waveform The worst case ripple is seen when the input voltage is at its lowest magnitude This is true if we can say that the output voltage stays relatively constant Design Example VO 28V VIN MIN 18V VIN NOM 24V VIN MAX 36V ILED 1A Buck Boost Convertion Ratio 5 Therefore 6...

Страница 6: ...cle Two methods of switch current sensing are available on the evaluation board The first is accomplished through the use of an external sense resistor which allows for higher accuracy in sensing the peak current For the LM3423 evaluation board the sense resistor R6 can be utilized using the jumper configuration as described in Table 4 Figure 4 External RSENSE ISW Current Sense Table 4 External RS...

Страница 7: ... with a pulse width modulated PWM signal By reducing the average LED current light from the LEDs is reduced This dimming method allows the converter to operate the LEDs at a specific peak output current level iL which is usually a set point determined by the LED manufacturer This allows the LED to illuminate with a consistent light color while still having the ability to reduce its lumens output T...

Страница 8: ... Fault Protection Flag The LM3423 can be configured with fault protection by using the fault flag indicator FLT pin 9 When a fault condition is detected the FLT pin will go high pulled up to VIN by resistor R2 5 8 Compensation The LM3423 s error amplifier EA is a transconductance type amplifier which allows for easy single pin compensation When a capacitor is used on the output of the converter to...

Страница 9: ...oltage protection OVP with programmable hysteresis feature is available on the LM3423 to protect the device from damage when the boosted output voltage goes above a maximum value The OVP threshold is set up by the resister divider network of R22 and R20 which is referenced to the regulated output voltage VO The OVP threshold and hysteresis can be programmed completely independent of each other OVP...

Страница 10: ...will therefore release when VO reaches 42V R20 562 kΩ R22 12 4 kΩ 5 11 Under Voltage Protection The LM3423 can be configured for under voltage lockout UVLO protection with hysteresis using the dimming input nDIM pin 8 and a resistor divider from input voltage to ground UVLO protects the power devices during power supply startup and shutdown to prevent operation at voltages less than the minimum op...

Страница 11: ...LO set point resistor divider When the UVLO pin exceeds 1 24V the current source is activated to instantly raise the voltage at the UVLO pin When the UVLO pin voltage falls below the 1 24V threshold the current source is turned off causing the voltage at the UVLO pin to fall The UVLO hysteresis range can be user adjusted using the gain resistor R26 Figure 10 UVLO Circuit During Normal Operation 11...

Страница 12: ... UVLO Circuit with R26 Populated for Small Hysteresis and Large Input Voltage 6 Evaluation Board Test Procedure Proper Board Connections Be sure to choose the correct wire size when connecting the source supply and load Monitor the current into and out of the unit under test UUT Monitor the voltages directly at the board terminals as resistive voltage drops along the wires may decrease measurement...

Страница 13: ...23 R3 Q7 Q4 VO R26 CONN1 LM3423 R29 C14 Q6 Z1 9 10 12 11 TIMR FLT LRDY DPOL VIN TP9 R2 TP11 C6 TP5 R15 J6 VIN J4B Q5 J4A R5 D2 J2 TP10 R20 OVP RPD VIN C18 R22 Q3 VO www ti com LM3432 Evaluation Board Schematic 7 LM3432 Evaluation Board Schematic Figure 12 LM3423 Evaluation Board All features and external components shown 13 SNVA376A December 2008 Revised May 2013 AN 1907 LM3423 Buck Boost Configur...

Страница 14: ...MOSFET TO 252 Vishay SUD40N10 25 E3 40A 100V Q3 SOT 23 200mA 40V Fairchild MMB3904 Q6 SOT 23 200mA 40V Fairchild MMB2907 Q7 Q9 N channel MOSFET SOT23 Fairchild 2N7002 200mA 60V R2 R3 R15 Resistor 0805 100 kΩ Vishay CRCW08051003F R5 0Ω R6 Resistor 2512 0 06Ω Vishay WSL2512R0600FEA R7 R8 Resistor 0805 1 kΩ Vishay CRCW08051001F R9 Resistor 1812 0 1 Panasonic ERJL12KF10CU R13 R31 R23 Resistor 0805 10k...

Страница 15: ... TP6 R31 VIN J5 VCC R23 R3 Q7 Q4 Q4 OVP RPD VIN C18 R22 Q3 VO VO R26 CONN1 www ti com LM3421 Buck Boost Design Example High Side Current Sense High Speed Dimming 9 LM3421 Buck Boost Design Example High Side Current Sense High Speed Dimming Figure 13 LM3421 Design Example High Side Current Sense with High Speed Dimming 15 SNVA376A December 2008 Revised May 2013 AN 1907 LM3423 Buck Boost Configurati...

Страница 16: ...1 R13 C5 L1 CONN2 C17 C1 R14 C8 VIN VIN PGND VIN TP8 R27 VO D1 C16 C7 C11 C4 R30 CONN1 LM3421 Buck Boost Design Example High Side Current Sense www ti com 10 LM3421 Buck Boost Design Example High Side Current Sense Figure 14 LM3421 Design Example High Side Current Sense 16 AN 1907 LM3423 Buck Boost Configuration Evaluation Board SNVA376A December 2008 Revised May 2013 Submit Documentation Feedback...

Страница 17: ...esponsible for compliance with all legal regulatory and safety related requirements concerning its products and any use of TI components in its applications notwithstanding any applications related information or support that may be provided by TI Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which anticipate dangerous consequences of failur...

Отзывы: