 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
SP6691EB Datasheet(PDF) 3 Page - Sipex Corporation |
|
||||||||||||||||||||||||||||||
SP6691EB Datasheet(HTML) 3 Page - Sipex Corporation |
|
|
3 / 6 page  3 Table 2. Suggested Low ESR capacitor MANUFACTURE PART NUMBER CAP /VOLTAGE SIZE /TYPE MURATA 770-436-1300 GRM32RR71E 225KC01B 2.2uF /25V 1210 /X5R MURATA 770-436-1300 GRM31CR61A 475KA01B 4.7uF /10V 1206 /X5R TDK 847-803-6100 C3225X7R1E 225M 2.2uF /25V 1210 /X7R TDK 847-803-6100 C3216X5R1A 475K 4.7uF /10V 1206 /X5R 7) LED Current Program In the white LEDs application, the SP6691EB is generally programmed as a current source. The bias resistor Rb is used to set the operating current of the white LED using the equation: F FB b I V R = where VFB is the feedback pin voltage (1.22V), IF is the operating current of the White LEDs. In order to achieve accurate LED current, 1% precision resistors are recommended. Table 3 below shows the Rb selection for different white LED currents. For example, to set the operating current to be 20mA, Rb is selected as 60.4 Ohm, as shown in the schematic. Table 3. Bias Resistor Selection IF (mA) Rb (Ω) 5 243 10 121 12 102 15 80.6 20 60.4 8) Vout Programming The SP6691EB can be programmed as either a voltage source or a current source. To program the SP6691 as voltage source, the SP6691 requires 2 feedback resistors R1 & R2 to control the output voltage. The formula for the resistor selection are shown below. 2 out 1 R 1 22 . 1 V R • − = 9) Open Circuit Protection When any white LED inside the white LED module fails or the LED module is disconnected from the circuit, the output and the feedback control will be open, thus resulting in a high output voltage, which may cause the SW pin 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 module. 10) Brightness Control Dimming control can be achieved by applying a PWM control signal to the EN/PWM pin. The brightness of the white LEDs is controlled by increasing and decreasing the duty cycle of The PWM signal. A 0% duty cycle corresponds to zero LED current and a 100% duty cycle corresponds to full load current. While the operating frequency range of the PWM control is from 60Hz to 700Hz, the recommended maximum brightness frequency range of the PWM signal 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 than the minimum SHDN voltage high. 11) Layout Consideration Both the input capacitor and the output capacitor should be placed as close as possible to the IC. This can reduce the copper trace resistance which directly affects the input and output ripples. The feedback resistor network should be kept close to the FB pin to minimize copper trace connections that can inject noise into the system. The ground connection for the feedback resistor network should connect directly to the GND pin or to an analog ground plane that is tied directly to the GND pin. The inductor and the schottky diode should be placed as close as possible to the switch pin to minimize the noise coupling to the other circuits, especially the feedback network. |
Similar Part No. - SP6691EB |
|
Similar Description - SP6691EB |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | 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 |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
