APA2068 datasheet(21/27 Pages) ANPEC

21 / 27 page

Rev. A.2 - Jul., 2005

APA2068

www.anpec.com.tw

Application Descriptions (Cont.)

constant can be relatively large. To reduce transients

in SE mode, an external 1k

Ω resistor can be placed in

parallel with the internal 10k

Ω resistor. The tradeoff

for using this resistor is an increase in quiescent current.

In the most cases, choosing a small value of Ci in the

range of 0.33

µF to 1µF, Cb being equal to 4.7µF and

an external 1k

Ω resistor should be placed in parallel

with the internal 10k

Ω resistor should produce a

virtually clickless and popless turn-on.

A high gain amplifier intensifies the problem as the

small delta in voltage is multiplied by the gain. So it

is advantageous to use low-gain configurations.

Shutdown Function

In order to reduce power consumption while not in use,

the APA2068 contains a shutdown pin to externally

turn off the amplifier bias circuitry. This shutdown

feature turns the amplifier off when a logic low is placed

on the SHUTDOWN pin. The trigger point between a

logic high and logic low level is typically 2.0V. It is

best to switch between ground and the supply V

DD to

provide maximum device performance.

By switching the SHUTDOWN pin to low, the amplifier

enters a low-current state, I

DD<1µA. APA2068 is in

shutdown mode, except PC-BEEP detect circuit.

On normal operating, SHUTDOWN pin pull to high

level to keeping the IC out of the shutdown mode.

The SHUTDOWN pin should be tied to a definite

voltage to avoid unwanted state changes.

Mute Function

The APA2068 mutes the amplifier outputs when logic

high is applied to the MUTE pin. Applying logic low to

the MUTE pin returns the APA2068 to normal

operation. Prevent unanticipated mute behavior by

connecting the Mute pin to logic high or low. Do not

let the Mute pin float.

Maximum Output Swing Clamping Function

(VolMax)

The APA2068 provide the maximum output swing

clamping function to protect the speaker.

When input a non-zero voltage (Vx) to VolMax pin,

the amplifier’s output amplitude (Vo) is be limited at

Vo = Vdd –Vx. This function can effective to limited

the output power across the speaker, and avoid

damaging the speaker.

The maximum setting voltage of VolMax is Vdd/2, and

when this function is not used, place the VolMax

connect to GND.

BTL Amplifier Efficiency

An easy-to-use equation to calculate efficiency starts

out as being equal to the ratio of power from the power

supply to the power delivered to the load.

The following equations are the basis for calculating

amplifier efficiency.

Where :

Efficiency of a BTL configuration :

Table 1 calculates efficiencies for four different output

power levels.

Note that the efficiency of the amplifier is quite low for

lower power levels and rises sharply as power to the

Optimizing Depop Circuitry (Cont.)

Efficiency =

PSUP

(9)

VORMS = √2

(10)

(11)

PSUP = VDD x IDDAVG = VDD x 2V

πRL

(

) / (VDD x

) =

PSUP

VPxVP

2RL

2VP

πRL

πVP

4VDD

(12)

O =

ORMS

O =

ORMS

APA2068 Datasheet(PDF) 21 Page - Anpec Electronics Coropration

APA2068 Datasheet(HTML) 21 Page - Anpec Electronics Coropration

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

Datasheet Download

Link URL