MAS9118 Просмотр технического описания (PDF) - Micro Analog Systems Oy

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MAS9118

Buzzer DAC Interface

Micro Analog Systems Oy 

The audio quality test is best performed by using the

build-in sine generator of the buzzer.exe program. It

is started by typing

EX]]HU ±S SRUW ±V IUHT ±D DWWHQ

where SRUW is the parallel port of the PC used for

the data transfer (0…3) and

#IUHT is the sine frequency in Hz and

#DWWHQ is the attenuation of the sine amplitude in dB

(≥ 0).

For example, a test signal using parallel port 1 of the

PC, having peak signal to noise ratio at 1000 Hz and

1 dB attenuation of the maximum level is obtained

by typing

EX]]HU ±S  ±V  ±D 

The wave files can be played by typing

EX]]HU ±Z ILOHZDY [-f/F] [-c/C] [-d/D]

where ILOHZDY is the name of an 8-bit wave file

(sample frequency 62.5 kHz) and

-f turns additional highpass filter on (default)

-F turns additional highpass filter off

-c turns dynamic compander on (default)

-C turns dynamic compander off

-d turns dynamic booster on

-D turns dynamic booster off (default)

Note that the wav file has to be in a specific format.

2QO\ WKH ZDY ILOHV ZLWK WKH VDPSOH UDWH RI 

N+] FDQ EH SOD\HG FRUUHFWO\ ZLWK WKH HYDOXDWLRQ

NLW VLQFH LWV FORFN IUHTXHQFLHV DUH IL[HG

Additionally the wav files have to be in mono and

signed 8-bit format. The conversion from the CD

quality data (44.1 kHz, 16-bit, stereo) to the

evaluation kit's format (62.5 kHz, 8-bit, mono) can

be easily made with the most of the audio softwares.

1RWH WKDW LI WKH ZDYH ILOH VSHFLILHG DIWHU Z

FDQQRW EH IRXQG WKH 3& KDV WR EH UHVWDUWHG LQ

RUGHU WR JHW WKH EX]]HUH[H SURJUDP WR UXQ

SURSHUO\ DJDLQ

At the nominal output voltage of 3.6 V the on-board

voltage regulator (R1) can deliver required current to

the class-D output stage of MAS9118. At higher

voltages (up to 5.5 V) an external voltage source

should be used if the load is as low as 8 Ohms. The

external voltage source should be connected

between the lower pin of the jumper X4 (jumper

short removed) and the left pin of the jumper X6

(board ground), see figure 2.

DAEV9118.001

29 January, 2002

X5

X4

X3

X6

MAS9118 Eval V2.0

JP1

buzzer

External power supply

+ 3.6-5.5 V

-

Figure 2.

'HOLYHUDEOHV

MAS9118 evaluation kit consists of the following

deliverables:

1

MAS9118 evaluation board V2.0 (2 pieces)

2

Control bus cable

3

Disk containing buzzer.exe, cwsdpmi.exe,

sample wave files and the data sheets of

MAS9118 and the evaluation kit

5HYLVLRQ QRWHV

Due to the class-D operation MAS9118 generates

some out-of-band noise, which may cause problems

for test equipment when using automatic scaling.

For example Audio Precision audio analyzer will

generate much additional distortion due to signal

overload when auto scaling is used. Auto scaling

does not take into account the existing high

frequency components causing wrong scaling and

leading to distortious signal clipping.

Also some test equipment can not synchronize to

the test sine frequency due to the out-of-band noise.

Usually a first order RC filter, when added before the

input of the test equipment, filters out the high

switching frequency. Remember to use high quality

components (especially capacitor) in order to

minimize the additional distortion caused by this

filter.

The evaluation board consumes about 0.5 A current

when the load is 8 Ohms. Use low ohmic wires from

power supply to the evaluation board.

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