APA2065KI-TY 查看數據表（PDF） - Anpec Electronics

零件编号

产品描述 (功能)

生产厂家

APA2065KI-TY

Stereo 2.7-W Audio Power Amplifier (with DC_Volume Control)

Anpec Electronics 

APA2065

Application Descriptions (Cont.)

Effective Bypass Capacitor, Cbypass (Cont.)

To avoid start-up pop noise occurred, the bypass

voltage should rise slower than the input bias voltage

and the relationship shown in equation (6) should be

maintained.

1

Cbypass x

125kΩ

<<

1

100kΩ

x

Ci

(6)

The bypass capacitor is fed thru from a 125kΩ resistor

inside the amplifier and the 100kΩ is maximum input

resistance of (Ri+ Rf). Bypass capacitor, Cb, values of

3.3µF to 10µF ceramic or tantalum low-ESR capacitors

are recommended for the best THD and noise

performance.

The bypass capacitance also effects to the start up

time. It is determined in the following equation:

Tstart up = 5 x (Cbypass x 125KΩ)

(7)

Output Coupling Capacitor, Cc

In the typical single-supply SE configuration, an output

coupling capacitor (Cc) is required to block the DC

bias at the output of the amplifier thus preventing DC

currents in the load. As with the input coupling capacitor,

the output coupling capacitor and impedance of the

load form a high-pass filter governed by equation.

FC(highpass)=

1

2πRLCC

(8)

For example, a 330µF capacitor with an 8Ω speaker

would attenuate low frequencies below 60.6Hz.The

main disadvantage, from a performance standpoint, is

the load impedance is typically small, which drives

the low-frequency corner higher degrading the bass

response. Large values of C are required topass low

C

frequencies into the load.

Power Supply Decoupling, Cs

The APA2065 provides two independent power inputs

for right channel and left channel used. PV is used

DD

for power amplifier only and VDD is used for volume

control amplifier and internal circuit excepting power

amplifier. The APA2065 is a high-performance

CMOS audio amplifier 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 causing by

long lead length between the amplifier and the speaker.

The optimum decoupling is achieved by using two

different type capacitors that target on different type

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 0.1µF placed as

close as possible to the device VDD lead works best.

For filtering lower-frequency noise signals, a large

aluminum electrolytic capacitor of 10µF or greater

placed near the audio power amplifier is recommended.

Optimizing Depop Circuitry

Circuitry has been included in the APA2065 to minimize

the amount of popping noise at power-up and when

coming out of shutdown mode. Popping occurs

whenever a voltage step is applied to the speaker. In

order to eliminate clicks and pops, all capacitors must

be fully discharged before turn-on. Rapid on/off

switching of the device or the shutdown function will

cause the click and pop circuitry.

The value of Ci will also affect turn-on pops (Refer to

Effective Bypass Capacitance). The bypass voltage

ramp up should be slower than input bias voltage.

Although the bypass pin current source cannot be

modified, the size of Cbypass can be changed to alter

the device turn-on time and the amount of clicks and

pops. By increasing the value of Cbypass, turn-on pop

can be reduced. However, the tradeoff for using a larger

bypass capacitor is to increase the turn-on time for

this device. There is a linear relationship between the

Copyright © ANPEC Electronics Corp.

18

Rev. A.4 - Aug., 2005

www.anpec.com.tw

Share Link: