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Summary of Contents for Texas Instruments LM3464
- Page 1 LM3464 Application Note 2071 LM3464A 4 Channel LED Driver Evaluation Board Literature Number: SNVA449C...
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Page 2: Highlight Features
The PCB of this evaluation board is pin to on the LED strings at 48V rail voltage, applying excessive in- pin compatible to both LM3464 and LM3464A with 80V and put voltage to this board will increase power dissipation on the 95V maximum input voltage respectively. -
Page 3: Evaluation Board Schematic
Evaluation Board Schematic 30127101 FIGURE 1. LM3464A Evaluation Board Schematic www.national.com... -
Page 4: Bill Of Materials
Bill of Materials Designation Description Package Manufacturer Part # Vendor LED Driver IC, LM3464A eTSSOP-28 eTSSOP-28 LM3464AMH Schottky Diode 40V 1.1A DO219AB DO219AB SL04-GS08 Vishay MOSFET N-CH 150V 29A D-PAK D-PAK FDD2572 Fairchild Q1,Q2,Q3,Q4 MOSFET N-CH 150V 50A TO252–3 TO252–3 IPD200N15N3 Infineon Cap MLCC 100V 2.2uF X7R 1210... - Page 5 Connectors and Test Pins 30127102 FIGURE 2. Typical Connection Diagram Evaluation Board Quick Setup Procedures Terminal Designation Description Power supply positive (+ve) connection PGND Power supply negative (-ve) connection AGND LM3464A analog signal ground LED1 Output Channel 1 (Connect to cathode of LED string 1) LED2 Output Channel 2 (Connect to cathode of LED string 2) LED3...
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Page 6: Structure Of The System
output voltage feedback. Figure 2 shows the voltage feed- Structure of the System back circuit using LM431 which has been widely used in A LM3464A LED lighting system is basically consist of three typical AC/DC power supplies as an example. main parts, the LM3464A evaluation board, an AC/DC power To reduce the output voltage of the AC/DC power supply from supply and an LED array containing four LED strings. - Page 7 RFB1 and DHC_READY RFB2 on the evaluation board and can be adjusted to any level below 80V / 95V (LM3464/LM3464A) as desired. By de- fault, the V is set at 48V. The V must set...
- Page 8 Connecting the LED Strings The LM3464A evaluation board is designed to drive 4 com- mon anode LEDs strings of 12 serial LEDs per string. The board includes four turret connectors, LED1, LED2, LED3 and LED4 for cathode connections of the LED strings. The anode of the LED strings should connect to the positive power output terminal of the AC/DC power supply.
- Page 9 The default value of the CTHM on the LM3464A evaluation Thermal Foldback Control board is 68nF, which set the thermal foldback dimming fre- The LM3464A evaluation board features an interface that en- quency at 258Hz. ables thermal foldback control by connecting a NTC thermal Thermal foldback control is activated when the voltage at the sensor to the THM+ and THM- terminals.
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Page 10: Design Example
Design Example 30127114 FIGURE 6. Attaching NTC Thermistor to the LEDs A NTC thermistor is connected to the THM+ and THM- ter- minals of the LM3464A evaluation board as shown in figure 6 to activate the thermal foldback control function. Assuming that thermal foldback control is required to begin at 70°C LED chassis temperature and reduce 55% average LED current (45% dimming duty cycle) when the chassis temper-... - Page 11 of minimum duty cycle limit is governed by the following equa- output channels are turned OFF. In cascade operation, the tion: DIM signal should only be applied to the MASTER unit. The LM3464A on the MASTER unit propagates the PWM dimming signal on its DIM pin to the slave units one by one through the SYNC pin.
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Page 12: Cascade Operation
Cascade Operation 30127162 FIGURE 8. Cascading LM3464A Evaluation Boards for Output Channel Expansion www.national.com... - Page 13 The total output power of the LED lighting system can be ex- If more than one slave unit is required, the SYNC pin of the panded by cascading the LM3464A evaluation boards. In first slave unit should connect to the DIM pin of the next slave cascade operation, the system involves one master unit and unit to allow propagation of the control signal along the system multiple slave units.
- Page 14 30127165 FIGURE 10. Additional Voltage Clamping Circuits for V > 80V/95V (LM3464A) RAIL(peak) evaluation board, the reverse voltage of the additional zener Applications With High Rail Voltage diodes must not exceed 95V. The resistors R Since the LM3464A is rated to 95V supply voltage, applying and R are resistors for absorbing the voltage a voltage to any pin of the device exceeding the absolute rated...
- Page 15 rent of the CMHZ5267B is 1.7mA at 75V zener voltage, the maximum allowable reverse current is 6.67mA at 500mW power dissipation. Thus, a standard 42.2kΩ resistor with 0.25W power rating Given that the input current of the DRx pins of the LM3464A (1206 package) and 1% tolerance can be used.
- Page 16 Typical Performance and Waveforms All curves taken at V = 48V with configuration in typical application for driving twelve power LEDs with four output channels active and output current per channel = 350mA. T = 25°C, unless otherwise specified. Output Current Variation Efficiency (%) 30127120 30127121...
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Page 17: Evaluation Board Layout
Evaluation Board Layout 30127126 FIGURE 11. Top Layer and Top Overlay 30127127 FIGURE 12. Bottom Layer and Bottom Overlay www.national.com... - Page 18 Notes www.national.com...
- Page 19 Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples...
- Page 20 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete.
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