APA2607 Datasheet, PDF (20/26 Pages) Anpec Electronics Coropration – 6W Stereo Class-D Audio Power Amplifier

APA2607
Application Information (Cont.)
Output Low-Pass Filter (Cont.)
OUTP ^18µH
2.2µF
OUTN ^18µH
4Ω
2.2µF
Figure 4. LC output filter for 4Ω speaker
Figure 3 and 4’s low pass filter cut-off frequency are 25kHz
(F_C).
F_C(lowpass)
=
2π
1
LC
(3)
printed circuit traces. Especial for the high slew rate out-
put PWM signal to speaker, these loops should be as
small as possible.
1. All components should be placed close to the APA2607.
For example, the input capacitor (C ) should be closed to
i
APA2607’s input pins to avoid causing noise coupling to
APA2607’s high impedance inputs; the decoupling ca-
pacitor (C_S) should be placed by the APA2607’s power pin
to decouple the power rail noise.
2. The output traces should be short, wide (>50mil) and
symmetric, and this loop like the figure 5, should be as
small as possible, (this loop is high slew rate and high
current path).
V_{DD C11}
1µF
C11 ^VDD
1µF
Power-Supply Decoupling Capacitor, C_S
The APA2607 is a high-performance CMOS audio ampli-
fier that requires adequate power supply decoupling to
ensure the output total harmonic distortion (THD) is as
low as possible. Power supply decoupling also prevents
the oscillations being caused by long lead length be-
tween the amplifier and the speaker.
The optimum decoupling is achieved by using two differ-
ent types of capacitors that target on different types of
noises on the power supply leads. For higher frequency
transients, spikes, or digital hash on the line, a good low
equivalent-series-resistance (ESR) ceramic capacitor,
typically 0.1µF placed as close as possible to the device
AVDD pin and 1mF placed to the LPVDD and RPVDD led
for works best. For filtering lower frequency noise signals,
a large aluminum electrolytic capacitor of 220µF or greater
placed near the audio power amplifier is recommended.
APA2607
Figure 5. TQFN5x5-32 Land Pattern Recommendation
3. The input trace should be short and symmetric.
4. The power trace width should greater than 50mil.
5. The TQFN5x5-32 Thermal PAD should be soldered on
PCB, and the ground plane needs soldered mask (to avoid
short-circuit) except the Thermal PAD area. Like the fig-
ure 6 illustrate.
Layout Recommendation
In high power Class-D power amplifier, a correct layout is
important to ensure proper operation of the amplifier and
avoid the switch noise radiation. In general, interconnect-
ing impedance should be minimized by using short, wide
Copyright © ANPEC Electronics Corp.
20
Rev. A.4 - Sep., 2011
www.anpec.com.tw