Datasheet LT3507 (Analog Devices) - 22

LT3507
applications inForMation
VIN SW VIN SW GND GND
(12a) (12b)
VSW V L1 IN SW IC1 C1 D1 C2 GND 3507 F12
(12c) Figure 12. Subtracting the Current When the Switch is ON (12a) From the Current When the Switch is OFF (12b) Reveals the Path of the High Frequency Switching Current (12c) Keep this Loop Small. The Voltage on the SW and Boost Nodes Will Also be Switched; Keep These Nodes as Small as Possible. Finally, Make Sure the Circuit is Shielded with a Local Ground Plane Figure 13. Power Path Components and Topside Layout PCB LAYOUT
components, along with the inductor and output capacitor, For proper operation and minimum EMI, care must be on the same side of the circuit board and connect them taken during printed circuit board (PCB) layout. Figure 12 on that layer. Place a local, unbroken ground plane below shows the high current paths in the step-down regula- these components and tie this ground plane to system tor circuit. Note that in the step-down regulators large, ground at one location, ideally at the ground terminal of switched currents flow in the power switch, the catch the output capacitor C2. Additionally, keep the SW and diode and the input capacitor. The loop formed by these BOOST nodes as small as possible. Figure 13 shows an components should be as small as possible. Place these example of proper PCB layout. 3507fb 22 For more information www.linear.com/LT3507