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ZXLD1350 - High Power LED Driver

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Overview of the ZXLD1350 LED driver, its basic operation, and key functions

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ZXLD1350 - High Power LED Driver

  1. 1. ZXLD1350 - High Power LED Driver <ul><li>Source: ZETEX Semiconductor </li></ul>
  2. 2. Introduction <ul><li>Purpose </li></ul><ul><ul><li>This training module overviews the ZXLD1350 LED driver, its basic operation, and key functions. </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>Key Features </li></ul></ul><ul><ul><li>Block Diagram </li></ul></ul><ul><ul><li>Basic Operations </li></ul></ul><ul><ul><li>PWM Dimming </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>15 pages </li></ul></ul>
  3. 3. Overview of ZXLD1350 <ul><li>Simple low parts count </li></ul><ul><li>Internal 30V NDMOS switch </li></ul><ul><li>350mA output current </li></ul><ul><li>Single pin on/off and brightness control using DC voltage or PWM </li></ul><ul><li>Internal PWM filter </li></ul><ul><li>Soft-start </li></ul><ul><li>High efficiency (up to 95%) </li></ul><ul><li>Wide input voltage range: 7V to 30V </li></ul><ul><li>40V transient capability </li></ul><ul><li>Output shutdown </li></ul><ul><li>Up to 1MHz switching frequency </li></ul><ul><li>Inherent open-circuit LED protection </li></ul><ul><li>Typical 4% output current accuracy </li></ul>
  4. 4. Internal Block Diagram LP filter
  5. 5. Applications <ul><li>Low voltage halogen replacement LEDs </li></ul><ul><li>Automotive lighting </li></ul><ul><li>Low voltage industrial lighting </li></ul><ul><li>LED back-up lighting </li></ul><ul><li>Illuminated signs </li></ul>
  6. 6. Typical Application Circuit
  7. 7. Operating waveforms
  8. 8. Reducing Output Ripple <ul><li>Peak to peak ripple current in the LED can be reduced by shunting a capacitor C led across the LED </li></ul><ul><li>Nominal ripple current is ±15mV/RS </li></ul><ul><li>Lower ripple can be achieved by a higher value capacitor </li></ul><ul><li>The capacitor will increase start-up delay </li></ul>Shunt capacitor C led = 1 µ F
  9. 9. Output current Adjustment by DC Control Voltage <ul><li>I OUTnom = 0.1/R S [for R S >0.27], where ADJ pin is floating </li></ul><ul><li>I OUTdc = 0.08*V ADJ /R S [for 0.3< V ADJ <2.5V] </li></ul>
  10. 10. Output current Adjustment by PWM <ul><li>Directly driving ADJ input (Fig-1) </li></ul><ul><li>Driving the ADJ input via open collector transistor (Fig-2) </li></ul><ul><li>Driving the ADJ input from MCU (Fig-3) </li></ul>Fig-1 Fig-2 Fig-3
  11. 11. PWM Dimming – Low Frequency Dimming <ul><li>The frequencyv of PWM signal must be greater than 100Hz and less than 1KHz. </li></ul><ul><li>The ADJ pin is driven with Low frequency PWM signal 0- V ADJ . </li></ul><ul><li>The input to the shutdown circuit to fall below its turn-off threshold, when the ADJ pin is low. </li></ul><ul><li>This results in an average output current I(outavg) proportional to PWM duty cycle </li></ul>
  12. 12. <ul><li>At PWM frequencies above 10Khz and duty cycle above 16% the output of internal Low pass filter will contain a DC component that is above shutdown threshold nominal output current will be proportional to average voltage at filter output, which is proportional to duty cycle. </li></ul>PWM Dimming – High Frequency Dimming
  13. 13. <ul><li>Shutdown mode: </li></ul><ul><li>Taking the ADJ pin to a voltage below 0.2V for more than approximately 100μs, will turn off the output. </li></ul><ul><li>Supply current will fall to a low standby level of 15μA nominal. </li></ul><ul><li>Soft-start: </li></ul><ul><li>The device has inbuilt soft-start action due to the delay through the PWM filter. </li></ul><ul><li>An external capacitor from the ADJ pin to ground will provide additional soft-start delay. </li></ul><ul><li>The time taken for the output to reach 90% of its final value is approximately 500μs. </li></ul>The graph shows the variation of soft-start time for different values of capacitor Shutdown / Soft-start Functions
  14. 14. ZXLD1350 Caculator Timing information     Turn on time (Ton) 0.28 µs Turn off time (Toff) 0.82 µs Duty cycle (D) 0.3   Switching frequency (f) 913.7 kHz LED current information     Maximum LED current 406.8 mA Minimum LED current 275.3 mA Peak-peak LED ripple current 131.5 mA Average LED current (Iavg) 341.0 mA Power distribution information   Output power 2.4 W Chip supply current 325.0 µA Power loss in switch 44.3 mW Switching power losses 125.4 mW Chip power dissipation 179.5 mW Power loss in diode 76.3 mW Power loss in sense resistor 34.9 mW Power loss in coil 58.1 mW Theoretical efficiency 87.3 % Input current 91.3 mA Additional outputs     Switch resistance at Tj 1.7 Ω Estimated die temperature (Tj) 54.8 ºC Input parameters - advanced     Ambient temperature (Tamb) 25.0 ºC Comparator L>H prop delay (TpdH) 50.0 ns Comparator H>L prop delay (TpdL) 50.0 ns LX voltage risetime (Tr) 20.0 ns LX voltage falltime (Tf) 30.0 ns LX switch resistance at Tamb 1.5 Ω Package thermal resistance (Ø jA) 166 ºC/W ADJ pin voltage (Vadj) 1.25 V Input parameters Supply voltage (Vin) 30.0 V No. of LEDs (N) 2   LED forward voltage (VLED) 3.5 V Free-wheel diode forward drop (Vf) 0.30 V Current sense resistor (Rs) 0.30 Ω Coil inductance (L) 47.0 µH Coil resistance (rL) 0.50 Ω
  15. 15. Additional Resource <ul><li>For ordering the ZXLD1350 LED driver, please click the part list or </li></ul><ul><li>Call our sales hotline </li></ul><ul><li>For additional inquires contact our technical service hotline </li></ul><ul><li>For more product information go to </li></ul><ul><ul><li>http://www.zetex.com/3.0/product_portfolio.asp?pno=ZXLD1350&h </li></ul></ul>

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