Moteur de recherche de fiches techniques de composants électroniques |
|
ST1208 Fiches technique(PDF) 6 Page - Sitronix Technology Co., Ltd. |
|
ST1208 Fiches technique(HTML) 6 Page - Sitronix Technology Co., Ltd. |
6 / 12 page ST1208 V1.1 6/12 2004/10/27 ! Applications Information Dimming Using EN1 and EN2 ( See Figure 1. ) Use EN1 and EN2 inputs as a digital 2-bit number to control on/off, 1/10, 3/10 and full current ( see Table1 ). RSET programs the full current level ( see the Setting the Output Current section ). EN1 EN2 BRIGHTNESS LED CURRENT 0 0 Shutdown ILED = 0 0 1 1/10 Brightness ILED = 16 X ISET 1 0 3/10 Brightness ILED = 48 X ISET 1 1 Full Brightness ILED = 160 X ISET Table 1. Brightness Control Dimming Using PWM into EN1 ( See Figure 2. ) Use EN2 for shutdown and drive EN1 with a PWM signal. Current can be varied from 1/10 to full. The maximum frequency of PWM is 10 KHz. ILED = K·ISET· ( 0.9·PWM + 0.1 ) Where K = 160, PWM = 0% ~ 100%. Dimming Using a Filtered PWM Signal ( See Figure 3. ) Use a high-frequency PWM signal to drive an R-C-R filter on the SET pin. A 0% PWM duty cycle corresponds to 20mA/LED, while a 100% PWM duty cycle corresponds to 0mA/LED. At PWM frequencies above 5 KHz, C may be reduced. Input Ripple ( See Figure 4. ) For LED drivers, input ripple is more important than output ripple. Input ripple depends on the source supply’s impedance. Adding a lowpass filter to the input further reduce input ripple. Figure 4 shows a C-R-C filter used to reduce input ripple to less than 2mVp-p when driving a heavy load or flash LED. PCB Layout and Routing The ST1208 is a high-frequency switched-capacitor voltage regulator. For best circuit performance, use a solid ground plane and place CIN and COUT as close to the ST1208 as possible. Also, place their ground pads close together and as close as possible to GND. Making the bias current clear can enhance stability of the LED output current, Component Selection For high efficiency performance, how to choose the component is the most important. Low ESR capacitor can reduce the output voltage ripple and increase the voltage of charge pump. The ceramic capacitor with an X5R or X7R is the best. The efficiency of 1x mode is over 15% higher than 1.5x mode. Therefore, higher input voltages or the low forward voltage of LED can make the ST1208 switch to 1x mode. Figure 1. Typical Operating Circuit Figure 2. Dimming Using PWM Signal into EN1 |
Numéro de pièce similaire - ST1208 |
|
Description similaire - ST1208 |
|
|
Lien URL |
Politique de confidentialité |
ALLDATASHEET.FR |
ALLDATASHEET vous a-t-il été utile ? [ DONATE ] |
À propos de Alldatasheet | Publicité | Contactez-nous | Politique de confidentialité | Echange de liens | Fabricants 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 |