 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
LD7889A Datasheet(PDF) 10 Page - Leadtrend Technology |
|
|
|||||||||||||||||||||||||||||
LD7889A Datasheet(HTML) 10 Page - Leadtrend Technology |
|
|
10 / 17 page  LD7889A 10 Leadtrend Technology Corporation www.leadtrend.com.tw LD7889A-DS-00 March 2012 The peak inductor current is sensed by measuring the voltage across the current-sense resistor RCS, which is connected from the source of external MOSFET to ground. LD7889A features leading edge blanking time to suppress the switching noise from the external MOSFET. A PWM comparator compares the current-sense voltage and the slop compensation signal with the output of the GM error amplifier. The device will turn off the external MOSFET when the voltage over CS exceeds the error amplifier’s output voltage. This process repeats in every switching cycle to achieve peak current-mode control. Programming the LED Current The LED current is programmable by placing a resistor between the ISET pin and ground. The ISET pin resistor is recommended to select in the range from 5k to 60k. Set the desired LED current according to the following equation: ) k ( R 1200 ) mA ( I ISET LED Fig. 11 LED Current vs. RISET RISET (K ) 120 160 200 240 0 40 80 0 20 40 60 80 100 120 Switching Frequency Selection LD7889A can operate in fixed frequency mode. The constant operation frequency is set by an external resistor connected between RT pin and ground. The resistor sets the charging current for internal oscillator. ) k ( RT 52000 ) kHz ( FSW Fig. 12 Frequency vs. RT RT (K ) 0 200 400 600 800 1000 0 200 400 600 800 1000 PWM dimming PWM dimming control is achieved by applying an external PWM signal of 100Hz to 25kHz to the PWM pin. Power Sequence and Timing Chart That is, the supply voltage must be applied to VIN pin before the dimming signal (to DIM pin) by at least 1ms and then the shutdown signal ( to EN pin). Please follow the proper power sequence in below timing chart. |
|
|
Link URL |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link to Datasheet | 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
