AW86225
October 2021 V1.9
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Application Information
Capacitors Selection
SUPPLY DECOUPLING CAPACITOR
（
C
S
）
The device requires adequate power supply decoupling. Place a low equivalent-series-resistance (ESR)
ceramic capacitor, typically 0.1μF. This choice of capacitor and placement helps with higher frequency
transients, spikes, or digital hash on the line. Additionally, placing this decoupling capacitor close to the device
is important, as any parasitic resistance or inductance between the device and the capacitor causes efficiency
loss. In addition to the 0.1μF ceramic capacitor, place a 10μF capacitor on the VDD supply trace. This larger
capacitor acts as a charge reservoir, providing energy faster than the board supply, thus helping to prevent
any droop in the supply voltage.
OUTPUT BEADS, CAPACITORS
The device output is a square wave signal, which causing switch current at the output capacitor, increasing
static power consumption, and therefore output capacitor should not be too large, 0.1nF ceramic capacitors is
recommended.
Bead
0.1nF
0.1nF
HDP
HDN
Bead
Wavefo rm
from chip
Wavefo rm After
PCB tra ce s
LRA
Wavefo rm afte r
bea ds
PCB tra ce s
PCB tra ce s
Figure 27 Ferrite Chip Bead and capacitor
The device output is a square wave signal. The voltage across the capacitor will be much larger than the VDD
voltage after increasing the bead capacitor. It suggested the use of rated voltage above 10V capacitor. At the
same time a square wave signal at the output capacitor switching current form, the static power consumption
increases, so the output capacitance should not be too much which is recommended 0.1nF ceramic capacitor
rated voltage of 10V.
If you want to get better EMI suppression performance, can use 1nF, rated voltage 10V
capacitor, but quiescent current will increase.
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