Preliminary Datasheet EL7801 (Intersil) - 8
| Manufacturer | Intersil |
| Description | High Power LED Driver |
| Pages / Page | 16 / 8 — EL7801. FIGURE 7. EXTERNAL OVP CIRCUIT. Over Temperature Shutdown. FIGURE … |
| File Format / Size | PDF / 412 Kb |
| Document Language | English |
EL7801. FIGURE 7. EXTERNAL OVP CIRCUIT. Over Temperature Shutdown. FIGURE 9. TEMPERATURE COMPENSATION CIRCUIT. Internal 5V LDO
Model Line for this Datasheet
Text Version of Document
EL7801
VBAT 0.47uF CREG Thermistor H u 0 VBAT FAULT L1 Close to 1 LED's VOUT VIN VIN VDC EL7801 SWD1 20uF COUT LDO E SWD2 S ZOVP N E .5 0 EL7801 S RT R 100K R1 + FB - + 100 E SWS1 RT SWS2 100K S N E .5 0 TEMP + S - R - RT 10K GND Temp Compensation
FIGURE 7. EXTERNAL OVP CIRCUIT Over Temperature Shutdown FIGURE 9. TEMPERATURE COMPENSATION CIRCUIT
An internal sense circuit disables PWM switching if the die In use, connect a potential divider comprised of an NTC temperature exceeds 135°C. Switching is re-enabled when thermistor and low temperature coefficient resistor between the temperature falls below 100°C. VDC and GND. Locate the thermistor physically close to the
Internal 5V LDO
LED load for accurate temperature sensing. Connect the tap point of the divider to the TEMP pin. Temperature changes An internal LDO between VIN and VDC regulates VDC to vary the VDC divider ratio and adjust the voltage present at 5V, to power control and gate drive circuits when VIN VTEMP, providing up to ±30% adjustment in FB bias level. A exceeds 5.1V. In normal operation decouple VDC with at 10K resistor and Muarta NCP18XH103f03RB thermistor will least 0.47µF. In applications where the input supply is less set VTEMP at VDC/2 at room temperature. Different than 5.5V, VDC should be tied directly to VIN. thermistor and resistor values may be used to tailor the
Temperature Compensation
system temperature coefficient for specific LED families. At a constant current, high power white LED light intensity Alternatively, temperature coefficient can be fine tuned by reduces as junction temperature increases. inserting limit resistors in series and parallel with the thermistor to bound impedance variation with temperature. For the LED temperature variation shown in Figure 8, a suitable arrangement is shown in Figure 11.
140 120 110 TPUT (%) 100 40 30% T OU 30 H 90 20 LIG 80 VE ION 70 10 TI T 60 0 RELA ARIA 50 V -10 -20 0 20 40 60 80 100 120 -20 BIAS JUNCTION TEMPERATURE, TJ (°C) % -30 -30% FIGURE 8. HIGH POWER WHITE LED LIGHT OUTPUT -40 0 0.2 0.4 0.6 0.8 1.0 VARIATION WITH JUNCTION TEMPERATURE VTEMP/VDC
EL7801 incorporates a supply referenced temperature
FIGURE 10. FB VOLTAGE VARIATION WITH VTEMP/VDC RATIO
interface to increase LED load current with temperature. Disable the function by connecting the TEMP pin to GND. 8 FN7354.0 December 22, 2005
VBAT 0.47uF CREG Thermistor H u 0 VBAT FAULT L1 Close to 1 LED's VOUT VIN VIN VDC EL7801 SWD1 20uF COUT LDO E SWD2 S ZOVP N E .5 0 EL7801 S RT R 100K R1 + FB - + 100 E SWS1 RT SWS2 100K S N E .5 0 TEMP + S - R - RT 10K GND Temp Compensation
FIGURE 7. EXTERNAL OVP CIRCUIT Over Temperature Shutdown FIGURE 9. TEMPERATURE COMPENSATION CIRCUIT
An internal sense circuit disables PWM switching if the die In use, connect a potential divider comprised of an NTC temperature exceeds 135°C. Switching is re-enabled when thermistor and low temperature coefficient resistor between the temperature falls below 100°C. VDC and GND. Locate the thermistor physically close to the
Internal 5V LDO
LED load for accurate temperature sensing. Connect the tap point of the divider to the TEMP pin. Temperature changes An internal LDO between VIN and VDC regulates VDC to vary the VDC divider ratio and adjust the voltage present at 5V, to power control and gate drive circuits when VIN VTEMP, providing up to ±30% adjustment in FB bias level. A exceeds 5.1V. In normal operation decouple VDC with at 10K resistor and Muarta NCP18XH103f03RB thermistor will least 0.47µF. In applications where the input supply is less set VTEMP at VDC/2 at room temperature. Different than 5.5V, VDC should be tied directly to VIN. thermistor and resistor values may be used to tailor the
Temperature Compensation
system temperature coefficient for specific LED families. At a constant current, high power white LED light intensity Alternatively, temperature coefficient can be fine tuned by reduces as junction temperature increases. inserting limit resistors in series and parallel with the thermistor to bound impedance variation with temperature. For the LED temperature variation shown in Figure 8, a suitable arrangement is shown in Figure 11.
140 120 110 TPUT (%) 100 40 30% T OU 30 H 90 20 LIG 80 VE ION 70 10 TI T 60 0 RELA ARIA 50 V -10 -20 0 20 40 60 80 100 120 -20 BIAS JUNCTION TEMPERATURE, TJ (°C) % -30 -30% FIGURE 8. HIGH POWER WHITE LED LIGHT OUTPUT -40 0 0.2 0.4 0.6 0.8 1.0 VARIATION WITH JUNCTION TEMPERATURE VTEMP/VDC
EL7801 incorporates a supply referenced temperature
FIGURE 10. FB VOLTAGE VARIATION WITH VTEMP/VDC RATIO
interface to increase LED load current with temperature. Disable the function by connecting the TEMP pin to GND. 8 FN7354.0 December 22, 2005
