Electronic Components Datasheet Search |
|
ISL97634IRT14Z-TK Datasheet(PDF) 7 Page - Intersil Corporation |
|
ISL97634IRT14Z-TK Datasheet(HTML) 7 Page - Intersil Corporation |
7 / 12 page ISL97634 7 FN6264.4 August 27, 2013 however, the dimming linearity is compromised at low duty cycles as their durations are too short for the ISL97634’s control loop to respond properly. This non-ideality behavior does not cause any functional problem. The PWM dimming linear responses in Figure 6 are expanded in Figure 11. At 1kHz PWM dimming, the duty cycle can virtually vary from below 1% to DC. On the other hand, at 20kHz PWM dimming, the linearity range is from 5% to DC only. The low level non-linearity effects at high frequency PWM dimming is also reflected in the efficiency measurements in Figure 12. Feedback Disconnect Switch The ISL97634 functions properly without using the FBSW. However, the output capacitor will discharge during the PWM off time resulting in poor dimming linearity at low duty cycles. The output discharge effect can be seen in Figure 13. Moreover, the output is modulated by the PWM signal that may create interference to other systems. . The FBSW should be used for PWM dimming as illustrated in the “Typical Application Circuit” on page 1. During the PWM off time, the FBSW is opened. The LEDs are floating and therefore the output capacitor has no path to discharge. The LED current responds accurately with the PWM signal (see Figure 14). The output switches very quickly to the target current with minimal settling ringing and without being modulated by the PWM signal, and therefore minimizes any system disturbance. Overvoltage Protection The ISL97634 comes with overvoltage protection. The OVP trip points are at 14V, 18V and 26V for ISL97634IRT14Z, ISL97634IRT18Z and ISL97634IRT26Z respectively. The maximum LED current and OVP threshold are shown in Table 1. When the device reaches the OVP, the LX stops switching, disabling the boost circuit until VOUT falls about 7% below the OVP threshold. At this point, LX will be allowed to switch again. The OVP event will not cause the device to shutdown. An output capacitor that is only rated for the required voltage range can therefore be used, which will optimize the component costs in some cases. FIGURE 11. DIMMING LINEARITY vs DUTY CYCLES ZOOM IN 0 1 2 3 4 5 6 7 8 9 10 02468 10 12 DUTY CYCLE (%) 7 LEDs VIN = 4V RSET = 4 Ω L = 10µH 20kHz 32kHz 1kHz FIGURE 12. EFFICIENCY vs PWM DIMMING FREQUENCIES 50 55 60 65 70 75 80 85 90 0 5 10 15 20 25 30 ILED (mA) VIN = 4V RSET = 4 Ω L = 22µH 3 LEDs ILED PWM/EN LX VOUT VIN = 4V R1 = 4 Ω L1 = 22µH FIGURE 13. PWM DIMMING AT 1kHz WITHOUT USING FBSW FIGURE 14. PWM DIMMING AT 1kHz USING FBSW ILED PWM/EN LX VOUT VIN = 4V R1 = 4 Ω L1 = 22µH |
Similar Part No. - ISL97634IRT14Z-TK |
|
Similar Description - ISL97634IRT14Z-TK |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |