Datasheet LT3479 (Analog Devices) - 10

LT3479
APPLICATIONS INFORMATION
MINIMIZE THE AREA TO VOUT OF THIS TRACE D COUT L1 CC SW GND C SW GND SS RC TO VS L SS V LT3479 V S C V FBN IN R1 R FBP C T TO V S IN SHDN VREF CIN RT R2 TO GND 3479 F04 TO SHDN PLACE VIAS AROUND EXPOSED PAD TO ENHANCE THERMAL PERFORMANCE
Figure 4. Suggested Board Layout Switching Frequency
IL 2A/DIV The switching frequency of the LT3479 is set by an exter- nal resistor attached to the RT pin. Do not leave this pin open. A resistor must always be connected for proper operation. See Table 4 and Figure 7 for resistor values VOUT and corresponding frequencies. 5V/DIV
Table 4. Switching Frequency
0.2MS/DIV 3479 F05
SWITCHING FREQUENCY (MHz) RT (kΩ) Figure 5. Start-Up with No Soft-Start Capacitor
3.5 1.78 3 2.87 IL 2.5 4.32 2A/DIV 2 6.49 1.5 10.2 1 17.8 VOUT 5V/DIV 0.5 39.2 0.2 113 0.2ms/DIV 3479 F06
Figure 6. Start-Up with CSS = 22nF
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