APA2177 Просмотр технического описания (PDF) - Anpec Electronics

Номер в каталоге

Компоненты Описание

производитель

APA2177

25mW Stereo Cap-Free Headphone Driver

Anpec Electronics 

APA2177

Application Information

Input Capacitor, Ci

In the typical application, an input capacitor, Ci, is required

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

DC level for optimum operation. In this case, C and the

i

minimum input impedance Ri from a high-pass filter with

the corner frequency are determined in the following

equation:

fC(highpass )

=

1

2πRifCi

(1)

The value of Ci is important to consider as it directly af-

fects the low frequency performance of the circuit. Ri is

the internal input resistance that typical value is 13.2KΩ

at 6dB and the specification calls for a flat bass response

down to 20Hz. Equation is reconfigured as below:

Ci

=

1

2πRifC

(2)

Consider

to

input

resistance

variation,

the

C

i

is

0.6µF

so

one would likely choose a value in the range of 0.6µF to

1µF. A further consideration for this capacitor is the leak-

age path from the input source through the input network

(Ri + Rf, Ci) to the load.

This leakage current creates a DC offset voltage at the

input to the amplifier that reduces useful headroom, es-

pecially in high gain applications. For this reason, a low

leakage tantalum or ceramic capacitor is the best choice.

When polarized capacitors are used, the negative side of

the capacitor should face the amplifier input in most ap-

plications as the DC level there is held at GND, which is

likely lower than the source DC level. Please note that it

is important to confirm the capacitor polarity in the

application.

The optimum decoupling is achieved by using two differ-

ent types of capacitor 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 0.1µF, is placed as close as possible to the de-

vice VDD lead for the best performance. For filtering lower

frequency noise signals, a large aluminum electrolytic

capacitor of 1µF or greater placed near the audio power

amplifier is recommended.

Charge pump flying capacitor, CCPF

The flying capacitor affects the load transient of the charge

pump. If the capacitor’s value is too small, then that will

degrade the charge pump’s current driver capability and

the performance of headphone drive amplifier.

Increasing the flying capacitor’s value will improve the

load transient of charge pump. It is recommend using

the low ESR ceramic capacitors (X7R type is

recommended) above 1µF.

Charge pump output capacitor, CCPO

The output capacitor’s value affects the power ripple di-

rectly at HPVSS. Increasing the value of output capacitor

reduce the power ripple. The ESR of output capacitor

affects the load transient of HPVSS. Lower ESR and

greater than 1µF ceramic capacitor is recommendation.

Power Supply Decoupling (C )

s

The APA2177 is a high-performance CMOS audio ampli-

fier that requires adequate power supply decoupling to

ensure the output total harmonic distortion (THD+N) is

as low as possible. Power supply decoupling also pre-

vents the oscillations causing by long lead length be-

tween the amplifier and the speaker.

Copyright © ANPEC Electronics Corp.

14

Rev. A.3 - Nov., 2017

www.anpec.com.tw

Share Link: