Other Parts Discussed in Thread: TPS62821, TPS568215
Dear TI :
I use tps55340 as boost circuit: 12 V ----> 24V 0.5A . efficiency>90%
use tps568215 as buck circuit: 12 V ---->5.2v 3A. another Buck circuit tps62821: 5.2V ---> 3.3V 1A
4 Level pcb layout. Schematic; Product:
but when i use Spectrum Analyzer detect the surface, Interference signal energy is large. (the wave1).
so i covered with Shield， the energy become lower but still have some glitch when detect on the shield surface。
i found the interference form TPS55340.
TPS55340: SW Waveform is not very bad( the wave 2.), the pcb Layout (The wave 3.) the freq.=460K
i have try some measurement But it can not finished the problem.
1. adjust the cap and resistor on the diode D90, cap: 10p---->1nf
2. add inductance 15uh on the output pin .
3. connect a bead on the diode D90.
Does the GND Net shout be optimize or not ? or give some advise .
thanks a lot .
