Datasheet ISL97634 (Intersil) - 6
| Fabricante | Intersil |
| Descripción | White LED Driver with Wide PWM Dimming Range |
| Páginas / Página | 12 / 6 — VOUT. PWM/EN. VIN = 4V R1 = 4. ILED. 1 = 22µH. IN = 4V. R1 = 4. L1 = … |
| Revisión | 13-11-2017 |
| Formato / tamaño de archivo | PDF / 891 Kb |
| Idioma del documento | Inglés |
VOUT. PWM/EN. VIN = 4V R1 = 4. ILED. 1 = 22µH. IN = 4V. R1 = 4. L1 = 22µH. VIN = 4V
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link to page 5 link to page 6 link to page 6 ISL97634 Typical Performance Curves (Continued)
VOUT VOUT LX LX PWM/EN PWM/EN VIN = 4V R1 = 4
ILED L V ILED 1 = 22µH IN = 4V R1 = 4
L1 = 22µH
FIGURE 8. PWM DIMMING AT 1kHz, D = 1% ZOOM IN FIGURE 9. PWM DIMMING AT 1kHz, D = 99%
VOUT LX R1 = 4
VIN = 4V L1 = 22µH PWM/EN ILED
FIGURE 10. PWM DIMMING AT 20kHz, D = 50% Detailed Description can be applied with an external PWM signal to pulse width modulated output current. It is well understood that the LED The ISL97634 uses a constant frequency, current mode brightness is a linear function of the LED current. In addition, control scheme to provide excellent line and load the average LED current corresponds to the duty cycle “D” of regulation. There are three OVP thresholds set at 14V, 18V the PWM signal as shown in Equation 2: and 26V respectively. The ISL97634 operates from an input VFB voltage of 2.4V to 5.5V and ambient temperature from -40°C I = -------- LED-AVG D R (EQ. 2) to +85°C. The switching frequency is around 1.45MHz and SET allows the driver circuit to employ small LC components. The As a result, PWM signal provides a means to dim the LED peak forward current of the LED is set using the RSET resistor. brightness. PWM dimming offers the best LEDs matching over In the steady state mode, the LED peak current is given by DC dimming. It is because the LED peak current operating Equation 1: point is far away from the knee of the diode I-V curve where V part to part variations are high. The PWM dimming test results I FB = -------- LED (EQ. 1) are shown in Figure 7 with two PWM frequencies, 1kHz and RSET 20kHz. The vertical scale parameter FB is proportional to the PWM Dimming current and therefore the brightness. The ISL97634’s PWM/EN pin can be tied permanently to high For the ISL97634, PWM dimming provides linear dimming for a fixed current operation. On the other hand, the ISL97634 adjustment with low frequency signal, such as 1kHz and below. The applied PWM dimming signal can be up to 32kHz; FN6264 Rev 4.00 Page 6 of 12 August 27, 2013
VOUT VOUT LX LX PWM/EN PWM/EN VIN = 4V R1 = 4
ILED L V ILED 1 = 22µH IN = 4V R1 = 4
L1 = 22µH
FIGURE 8. PWM DIMMING AT 1kHz, D = 1% ZOOM IN FIGURE 9. PWM DIMMING AT 1kHz, D = 99%
VOUT LX R1 = 4
VIN = 4V L1 = 22µH PWM/EN ILED
FIGURE 10. PWM DIMMING AT 20kHz, D = 50% Detailed Description can be applied with an external PWM signal to pulse width modulated output current. It is well understood that the LED The ISL97634 uses a constant frequency, current mode brightness is a linear function of the LED current. In addition, control scheme to provide excellent line and load the average LED current corresponds to the duty cycle “D” of regulation. There are three OVP thresholds set at 14V, 18V the PWM signal as shown in Equation 2: and 26V respectively. The ISL97634 operates from an input VFB voltage of 2.4V to 5.5V and ambient temperature from -40°C I = -------- LED-AVG D R (EQ. 2) to +85°C. The switching frequency is around 1.45MHz and SET allows the driver circuit to employ small LC components. The As a result, PWM signal provides a means to dim the LED peak forward current of the LED is set using the RSET resistor. brightness. PWM dimming offers the best LEDs matching over In the steady state mode, the LED peak current is given by DC dimming. It is because the LED peak current operating Equation 1: point is far away from the knee of the diode I-V curve where V part to part variations are high. The PWM dimming test results I FB = -------- LED (EQ. 1) are shown in Figure 7 with two PWM frequencies, 1kHz and RSET 20kHz. The vertical scale parameter FB is proportional to the PWM Dimming current and therefore the brightness. The ISL97634’s PWM/EN pin can be tied permanently to high For the ISL97634, PWM dimming provides linear dimming for a fixed current operation. On the other hand, the ISL97634 adjustment with low frequency signal, such as 1kHz and below. The applied PWM dimming signal can be up to 32kHz; FN6264 Rev 4.00 Page 6 of 12 August 27, 2013