LT3045 datasheet(21/45 Pages) AD

21 / 45 page

Data Sheet

LT83201

analog.com

Rev. A 21 of 45

If transient performance is not critical, other passive filter solutions can be realized using a physical inductor as a

larger second L and additional output capacitance for the second C, as shown in Figure 50.

Figure 50. Additional Output Ripple Filtering Using a Second LC Filter

When designing an additional filter for further attenuation of the switching ripple, it is highly recommended to design

with LTpowerCAD® to ensure that the design is stable with good phase margin and provides sufficient attenuation at

the switching frequency of interest.

The Silent Switcher 3 architecture makes it possible to achieve excellent noise performance from low to high

frequencies at the output of the LT83201 while utilizing only passive filtering.

PCB Layout Recommendations

The LT83201 is specifically designed to minimize low-frequency (10Hz to 100kHz) noise and EMI emissions and

maximize efficiency when switching at high frequencies. For optimal performance, the LT83201 can use multiple VIN

bypass capacitors.

Two small capacitors are placed as close as possible to the LT83201 VIN pins, and the third capacitor with a larger

value, 4.7μF or higher, should be placed near one of these two capacitors. For a recommended PCB layout, see Figure

51.

For more details and PCB design files, refer to the LT83201 demo board manual. Note that large, switched currents

flow in the LT83201 VIN and GND pins and the input capacitors. The loops formed by the input capacitors should be

as small as possible by placing the capacitors adjacent to the VIN and GND pins. Capacitors with small case sizes, such

as 0402 or 0603, are optimal due to their low parasitic inductance. Special care must be taken with the input

capacitors to ensure they have a low-impedance return path to the IC ground. This is achieved by placing several

grounds through the GND side of the input capacitors such that the ground plane is utilized to full advantage. This

should be an unbroken ground plane with a solid connection to the exposed pad of the IC, as shown in Figure 51.

LT83201

GND

OUTS

2.2µH

0.1µH

DISCRETE L

22µF

OPTIONAL

VOUT

LT3045 Datasheet(PDF) 21 Page - Analog Devices