APA6003 datasheet(13/22 Pages) ANPEC

13 / 22 page

Rev. P.1 - Sep., 2015

www.anpec.com.tw

APA6003

Application Information

Input Resistance, R

Changing the gain setting can vary the input resistance

of the amplifier from its smallest value, 9 k

Ω ±20%, to the

largest value, 60 k

Ω ±20%. As a result, if a single capaci-

tor is used in the input high-pass filter, the -3 dB or cutoff

frequency may change when changing gain steps.

Input Capacitor, C

In the typical application, an input capacitor C

i is required

to allow the amplifier to bias the input signal to the proper

dc level for optimum operation. In this case, C

i and the

input impedance of the amplifier (R

I) form a high-pass

filter with the corner frequency determined in Equation 1.

The value of C

I is important, as it directly affects the bass

(low-frequency) performance of the circuit. Consider the

example where R

I is 60 kΩ and the specification calls for

a flat bass response down to 20 Hz. Equation 1 is

reconfigured as Equation 2.

)

hipass

(

(1)

In this example, C

I is 0.13 µF; so, one would likely choose

a value of 0.15

µF as this value is commonly used. If the

gain is known and is constant, use R

I from Table 1 to

calculate C

I. A further consideration for this capacitor is

the leakage path from the input source through the input

network C

I and the feedback network to the load. This

leakage current creates a dc offset voltage at the input to

the amplifier that reduces useful headroom, especially

in high gain applications. For this reason, a low-leakage

tantalum or ceramic capacitor is the best choice. When

polarized capacitors are used, the positive side of the

capacitor should face the amplifier input in most applica-

tions as the dc level there is held at V

CLAMP

/2, which is

likely higher than the source dc level. Note that it is impor-

tant to confirm the capacitor polarity in the application.

Additionally, lead-free solder can create dc offset volt-

ages and it is important to ensure that boards are cleaned

properly.

(2)

Figure 3. Ferrite Bead Output Filter

Output Low-Pass Filter

If the traces form APA6003 to speaker are short, it doesn

’t

require output filter for FCC & CE standard.

A ferrite bead may need if it

’s failing the test for FCC or CE

tested without the LC filter. The figure 2 is the sample for

added ferrite bead; the ferrite show choosing high im-

pedance in high frequency.

Power-Supply Decoupling Capacitor, C

The APA6003 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 different types of

capacitors that target on different types of noise 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.

µF placed as close as possible to the device AVDD pin

and 1

µF placed to the LPVDD and RPVDD leads for works

best. For filtering lower frequency noise signals, a large

aluminum electrolytic capacitor of 220

µF or greater placed

near the audio power amplifier is recommended.

OUTN

1nF

Ferrite

Bead

Ferrite

Bead

OUTP

Ω

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