Electronic Components Datasheet Search |
|
LT3465A Datasheet(PDF) 8 Page - Linear Technology |
|
LT3465A Datasheet(HTML) 8 Page - Linear Technology |
8 / 12 page LT3465/LT3465A 8 3465af APPLICATIO S I FOR ATIO Figure 8. Recommended Component Placement Dimming Using Direct PWM (LT3465A) Unlike the LT3465, the LT3465A does not have internal soft-start. Although the input current is higher during start- up, the absence of soft-start allows the CTRL pin to be directly driven with a PWM signal for dimming. A zero percent duty cycle sets the LED current to zero, while 100% duty cycle sets it to full current. Average LED current increases proportionally with the duty cycle of the PWM signal. PWM frequency should be between 1kHz and 10kHz for best performance. The PWM signal should be at least 1.8V in magnitude; lower voltage will lower the feedback voltage as shown in Equation 1. Waveforms are shown for a 1kHz PWM and 10kHz PWM signal in Figures 7a and 7b respectively. 1 COUT L RFB 2 3 6 5 4 CIN GND 3465A F08 VIN CTRL minimize the input current. VOUT and input current during output open circuit are shown in the Typical Performance Characteristics. Board Layout Consideration As with all switching regulators, careful attention must be paid to the PCB board layout and component placement. To maximize efficiency, switch rise and fall times are made as short as possible. To prevent electromagnetic interfer- ence (EMI) problems, proper layout of the high frequency switching path is essential. Place COUT next to the VOUT pin. Always use a ground plane under the switching regulator to minimize interplane coupling. In addition, the ground connection for the feedback resistor R1 should be tied directly to the GND pin and not shared with any other component, ensuring a clean, noise-free connection. Rec- ommended component placement is shown in Figure 8. Figure 7a. Figure 7b. FB 100mV/DIV CTRL 2V/DIV 200 µs/DIV (1kHz) 3465A F07a FB 100mV/DIV CTRL 2V/DIV 20 µs/DIV (10kHz) 3465A F07b LT3465A CTRL PWM Start-Up Input Current (LT3465A) As previously mentioned, the LT3465A does not have an internal soft-start circuit. Inrush current can therefore rise to approximately 400mA as shown in Figure 9 when driving 4 LEDs. The LT3465 has an internal soft-start circuit and is recommended if inrush current must be minimized. Open-Circuit Protection The LT3465 and LT3465A have an internal open-circuit protection circuit. In the cases of output open circuit, when the LEDs are disconnected from the circuit or the LEDs fail, the VOUT is clamped at 30V. The LT3465 and LT3465A will then switch at a very low frequency to Figure 9. FB 200mV/DIV CTRL 2V/DIV 50 µs/DIV 3465A F09 IIN 200mV/DIV |
Similar Part No. - LT3465A |
|
Similar Description - LT3465A |
|
|
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 |