Datasheet SP6690 (Sipex) - 10
| Fabricante | Sipex |
| Descripción | Micro Power Boost Regulator Series White LED Driver |
| Páginas / Página | 15 / 10 — APPLICATION INFORMATION. OUT (V). R1 (. R2 (. IF (mA). Rb (. Brightness … |
| Formato / tamaño de archivo | PDF / 384 Kb |
| Idioma del documento | Inglés |
APPLICATION INFORMATION. OUT (V). R1 (. R2 (. IF (mA). Rb (. Brightness Control. Output Voltage Program. Open Circuit Protection
Línea de modelo para esta hoja de datos
Versión de texto del documento
APPLICATION INFORMATION
precision resistors are recommended. Table 3 Table 4. Divider Resistor Selection below shows the Rb selection for different white LED currents. For example, to set the operating current to be 20mA, R
V
b is selected as 60.4 Ω, as
OUT (V) R1 (
Ω
) R2 (
Ω
)
shown in the schematic. 12 1M 113K 15 1M 88.7K Table 3. Bias Resistor Selection 18 1M 73.2K 21 1M 61.9K
IF (mA) Rb (
Ω
)
30 1M 42.2K 5 243 10 121
Brightness Control
12 102 Dimming control can be achieved by applying a 15 80.6 PWM control signal to the SHDN pin. The brightness of the white LEDs is controlled by 20 60.4 increasing and decreasing the duty cycle of The PWM signal. A 0% duty cycle corresponds to
Output Voltage Program
zero LED current and a 100% duty cycle corre- The SP6690 can be programmed as either a sponds to full load current. While the operating voltage source or a current source. To program frequency range of the PWM control is from the SP6690 as voltage source, the SP6690 re- 60Hz to 700Hz, the recommended maximum quires 2 feedback resistors R brightness frequency range of the PWM signal 1 & R2 to control the output voltage. As shown in Figure 22. is from 60Hz to 200Hz. A repetition rate of at least 60Hz is required to prevent flicker. The magnitude of the PWM signal should be higher VIN D1 than the minimum SHDN voltage high. L1 VOUT
Open Circuit Protection
C2 R1 When any white LED inside the white LED C1 U1 5 1 module fails or the LED module is disconnected V SW I N from the circuit, the output and the feedback SP6690 4 3 SHDN FB control will be open, thus resulting in a high 1.22V G ND output voltage, which may cause the SW pin R2 2 voltage to exceed it maximum rating. In this case, a zener diode can be used at the output to limit the voltage on the SW pin and protect the part. The zener voltage should be larger than the maximum forward voltage of the White LED
Figure 22. Using SP6690 as Voltage Source
module. The formula and table for the resistor selection are shown below: R1 =( VOUT - 1 ) • R2 1.22 Date: 08/31/09 SP6690 Micro Power Boost Regulator, Series White LED Driver © Copyright 2005 Sipex Corporation 10
precision resistors are recommended. Table 3 Table 4. Divider Resistor Selection below shows the Rb selection for different white LED currents. For example, to set the operating current to be 20mA, R
V
b is selected as 60.4 Ω, as
OUT (V) R1 (
Ω
) R2 (
Ω
)
shown in the schematic. 12 1M 113K 15 1M 88.7K Table 3. Bias Resistor Selection 18 1M 73.2K 21 1M 61.9K
IF (mA) Rb (
Ω
)
30 1M 42.2K 5 243 10 121
Brightness Control
12 102 Dimming control can be achieved by applying a 15 80.6 PWM control signal to the SHDN pin. The brightness of the white LEDs is controlled by 20 60.4 increasing and decreasing the duty cycle of The PWM signal. A 0% duty cycle corresponds to
Output Voltage Program
zero LED current and a 100% duty cycle corre- The SP6690 can be programmed as either a sponds to full load current. While the operating voltage source or a current source. To program frequency range of the PWM control is from the SP6690 as voltage source, the SP6690 re- 60Hz to 700Hz, the recommended maximum quires 2 feedback resistors R brightness frequency range of the PWM signal 1 & R2 to control the output voltage. As shown in Figure 22. is from 60Hz to 200Hz. A repetition rate of at least 60Hz is required to prevent flicker. The magnitude of the PWM signal should be higher VIN D1 than the minimum SHDN voltage high. L1 VOUT
Open Circuit Protection
C2 R1 When any white LED inside the white LED C1 U1 5 1 module fails or the LED module is disconnected V SW I N from the circuit, the output and the feedback SP6690 4 3 SHDN FB control will be open, thus resulting in a high 1.22V G ND output voltage, which may cause the SW pin R2 2 voltage to exceed it maximum rating. In this case, a zener diode can be used at the output to limit the voltage on the SW pin and protect the part. The zener voltage should be larger than the maximum forward voltage of the White LED
Figure 22. Using SP6690 as Voltage Source
module. The formula and table for the resistor selection are shown below: R1 =( VOUT - 1 ) • R2 1.22 Date: 08/31/09 SP6690 Micro Power Boost Regulator, Series White LED Driver © Copyright 2005 Sipex Corporation 10