4

DA9191EB.006

June 30,1997

FUNCTIONS

x Battery Charging

If a battery is used to power MAS9129, the battery

may be charged by connecting the battery charger to

the

charger

input.

The

battery charging

circuit

monitors the battery voltage level. When a negative

slope in the charging curve is detected, the charging is

stopped. The battery will be charged to 1 volt above

the nominal battery voltage level. The current into

MAS9129 can be monitored by jumper CM4.

x MAS9129 Regulators

The voltage and current levels of the MAS9129

regulators can be measured at test points CM1 and

CM2. Remove the jumper and insert an ammeter to

monitor the current values. Regulator 2 is enabled by

jumper J2.

x Microphone Interface

On the evaluation board there are three possibilities

for testing the microphone amplifier interface. The first

way is with an on-board microphone interface, which

may not be used in normal mode, but exhibits one way

of implementing an interface to a microphone by using

an external anti-aliasing filter. This microphone uses a

DC voltage from a basic voltage divider. The diagram

for this interface can be found in the schematic

section.

Another

possibility

is

to

use

external

microphone circuitry with the MAS9191A microphone

amplifier using connector J1. This is done by removing

the jumpers and connecting the microphone signal to

pin 2 and the feedback signal to pin 1. The third

possibility is to use the external microphone input

EXTMIC. The electrical characteristics of the EXTMIC

and MIC pins are found from the MAS9191A data

sheet.

x Earphone Interface

The BNC-type and the header type connectors are

assembled for differential type earphone output. An

external earphone is supplied with the evaluation

board. The board is capable of driving this earphone

as well as other models directly at a 3V operation

voltage. Use the BNC connector EXTEARP for

external earphones. Detailed electrical descriptions of

these interfaces are found from the MAS9191A data

sheet.

x Buzzer Interface

The buzzer is driven by transistor Q1. The model of

Q1 and the value of resistors R9 and R10 will affect

the levels of the buzzer tone significantly. To test an

external buzzer, connect it to the buzzer input pin.

x Side Tone Circuit

The source of the side tone is recommended to be

taken from MICOUT of the MAS9191A located at pin

T2. The level of the side tone is controlled by the

external circuitry shown in the schematic section. The

level and the frequency response of the side tone can

be controlled by changing the values of components

R11, R12,C43 and C44.

x RX and TX Interfaces

Two BNC connectors allow easy interface to RF

sections or to a radio test system. The transmit audio

signal as well as DTMF, ST, SAT and send messages

may be monitored at the Tx connector. The receive

audio signal as well as SAT and receive messages

are measured by applying the signals to the RX

connector. There are 22nF DC blocking capacitors on

both interfaces. The electrical characteristics can be

found from the MAS9191A data sheet.

x Microphone and Rx Audio Level Measurement

The

two

internal

operational

amplifiers

of

the

MAS9191A are used to measure audio levels. The

level measurement is done with the circuit shown in

the schematic section. The level detection output is

monitored by the micro controller A/D converter. To

examine the operation of the level detector, measure

test points T6 and T7.

x Test Points

There are seven test points along the Rx and Tx audio

section. These test points can be used to measure

gain control levels and the performance of the

compressor, expander, limiter and all filters. The pin

description section defines all test points.

x CTRL Interface

The CTRL connector consists of the control signal

TXCTRL for the transmitter and two test indicators

BUSY and TXON. TXCTRL is an open collector output

and is low only when a transmission collision occurs.

After a collision TXCTRL goes to a high impedance

state and the TX block of the MAS9191A is reset with

TXRST.

x Three 8-bit DAC Outputs

The DAC connector contains a direct interface to the

three MAS9191A internal 8-bit DACs.

x MAS9191A Serial Bus Interface

The five row jumper for the MAS9191A serial bus to

the micro controller is normally closed. Remove the

jumpers for external control. The STB, SCL, SRXD,

STXD and XINT signals are located at pins 1, 2, 3, 4

and 5 respectively.

x MS8323 Output Frequency

The output frequency of the VCTCXO can be

measured from test pin OSCOUT. The DAC1 output

from MAS9191A is the voltage control for the

VCTCXO which adjusts the output frequency. Jumper

of the VCTCXO can be measured through jumper

CM5.