APA6003 datasheet(14/22 Pages) ANPEC

14 / 22 page

Rev. P.1 - Sep., 2015

www.anpec.com.tw

APA6003

Application Information (Cont.)

Output Low-Pass Filter (cont.)

Figure 4 and Figure 5 are examples for added the LC

filter (Butterworth), it

’s recommended for the situation that

the trace form amplifier to speaker is too long, and needs

to eliminate the radiated emission or EMI.

Figure 4. Typical LC Output Filter, Cutoff Frequency of

27 kHz, Speaker Impedance = 8

Ω

µF

µH

OUTN

OUTP

Ω

2.2

µF

2.2

µF

µH

OUTN

OUTP

Ω

Figure 5. Typical LC Output Filter, Cutoff Frequency of

27 kHz, Speaker Impedance = 4

Ω

BSN and BSP Capactiors

Layout Recommendation

The APA6003 can be used with a small, inexpensive fer-

rite bead output filter for most applications. However,

since the Class-D switching edges are fast, it is neces-

sary to take care when planning the layout of the printed

circuit board. The following suggestions will help to meet

EMC requirements.

1. The high frequency decoupling capacitors should be

placed as close to the PVDD and AVDD terminals as

possible. Large (100

µF or greater) bulk power supply

decoupling capacitors should be placed near the

APA6003 on the LPVDD and RPVDD supplies. Local, high-

frequency bypass capacitors should be placed as close

to the PVDD pins as possible. These caps can be con-

nected to the thermal pad directly for an excellent ground

connection. Consider adding a small, good quality low

ESR ceramic capacitor between 1000pF and 10nF and a

larger mid-frequency cap of value between 0.1

µF and

µF also of good quality to the PVDD connections at each

end of the chip.

2. Keep the current loop from each of the outputs through

the ferrite bead and the small filter cap and back to PGND

as small and tight as possible. The size of this current

loop determines its effectiveness as an antenna.

3. Grounding - The AVDD (pin 7) decoupling capacitor

should be grounded to analog ground (AGND). The PVDD

decoupling capacitors should connect to PGND. Analog

ground and power ground should be connected at the

thermal pad, which should be used as a central ground

connection or star ground for the APA6003.

4. Output filter - The ferrite EMI filter (Figure 3) should be

placed as close to the output terminals as possible for

the best EMI performance. The LC filter (Figure 4 and

Figure 5) should be placed close to the outputs. The ca-

pacitors used in both the ferrite and LC filters should be

grounded to power ground.

The full H-bridge output stages use only NMOS

transistors. Therefore, they require bootstrap capacitors

for the high side of each output to turn on correctly. A 0.

µF ceramic capacitor, rated for at least 25 V, must be

connected from each output to its corresponding boot-

strap input. Specifically, one 0.22

µF capacitor must be

connected from OUTP to BSP, and one 0.22

µF capacitor

must be connected from OUTN to BSN.

The bootstrap capacitors connected between the BSP or

BSN pins and corresponding output function as a float-

ing power supply for the high-side N-channel power

MOSFET gate drive circuitry.

During each high-side switching cycle, the bootstrap ca-

pacitors hold the gate-to-source voltage high enough to

keep the high-side MOSFETs turned on.

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