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HDSP-4501-JI000 Datasheet(PDF) 8 Page - Agilent(Hewlett-Packard) |
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HDSP-4501-JI000 Datasheet(HTML) 8 Page - Agilent(Hewlett-Packard) |
8 / 8 page Operational Considerations Electrical Description These display devices are com- posed of light emitting diodes, with the light from each LED optically stretched to form individual dots. These display devices are well suited for strobed operation. The typical forward voltage values can be scaled from Figure 2. These values should be used to calculate the current limiting resistor value and the typical power dissipation. Expected maximum VF values, for driver circuit design and maximum power dissipation, may be calculated using the following VFMAX models: AlGaAs Red (HDSP-M10x): VFMAX = 1.8 V + IPEAK(20 Ω) For IPEAK ≤ 20 mA VFMAX = 2.0 V + IPEAK(10 Ω) For IPEAK ≥ 20 mA HER (HDSP-450x): VFMAX = 1.75 V + IPEAK(35 Ω) For IPEAK ≥ 5 mA Green (HDSP-510x): VFMAX = 1.75 V + IPEAK(38 Ω) For IPEAK ≥ 5 mA Figure 3 allows the designer to calculate the luminous intensity at different peak and average currents. The following equation calculates intensity at different peak and average currents: IVAVG = (IFAVG/IFAVG DATA SHEET)( η PEAK)(IV DATA SHEET) Where: IFAVG is the desired time averaged LED current. IFAVG DATA SHEET is the time averaged data sheet test current for IVDATA SHEET. η PEAK is the relative efficiency at the peak current, scaled from Figure 3. IV DATA SHEET is the time averaged data sheet luminous intensity, resulting from IFAVG DATA SHEET. IVAVG is the calculated time averaged luminous intensity resulting from IFAVG. For example, what is the luminous intensity of an AlGaAs Red (HDSP- L10X) driven at 50 mA peak 1/5 duty factor? IFAVG = 50 mA * 0.2 = 10 mA IFAVG DATA SHEET = 2 mA η PEAK = 0.98 IV DATA SHEET = 1650 µcd Therefore IVAVG = (10 mA/2 mA)(0.98) (1650 µcd) = 8085 µcd Thermal Considerations The device thermal resistance may be used to calculate the junction temperature of the central LED. The equation below calculates the junction temperature of the central (hottest) LED. TJ =TA + (PD)(RθJ-A)(N) PD =(VFMAX)(IFAVG) R θ J-A = RθJ-PIN+ RθPIN-A TJ is the junction temperature of the central LED. TA is the ambient temperature. PD is the power dissipated by one LED. N is the number of LEDs ON per character. VFMAX is calculated using the appropriate VF model. R θ J-A is the package thermal resistance from the central LED to the ambient. R θ J-PIN is the package thermal resistance from the central LED to pin. R θ PIN-A is the package thermal resistance from the pin to the ambient. For example, what is the maximum ambient temperature an HDSP- L10X can operate with the following conditions: IPEAK = 125 mA IFAVG = 10 mA R θ J-A = 50°C/W N = 35 TJMAX = 110°C VFMAX = 2.0 V + (0.125 A)(10) = 3.25 V PD = (3.25 V)(0.01 A) = 0.0325 W TA = 110°C – (50 °C/W)(0.0325 W)(35) = 53 °C The maximum number of dots ON for the ASCII character set is 20. What is the maximum ambient temperature an HDSP-L10X can operate with the following conditions: IPEAK = 125 mA IFAVG = 10 mA R θ J-A = 50°C/W N = 20 TJMAX = 110°C VFMAX = 3.25 V PD = 0.0325 W TA = 110°C – (50 °C/W)(0.0325 W)(20) = 77 °C Therefore, the maximum ambient temperature can be increased by reducing the average number of dots ON from 35 to 20 dots ON per display. Contrast Enhancement For information on contrast enhancement, please see Application Note 1015. Soldering/Cleaning For Soldering/Cleaning information on soldering LEDs, please refer to Application Note 1027. www.agilent.com/semiconductors E-mail: SemiconductorSupport@agilent.com Data subject to change. Copyright © 2004 Agilent Technologies, Inc. Obsoletes 5988-2224EN July 8, 2004 5988-5215EN For product information and a complete list of Agilent contacts and distributors, please go to our web site. |
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