MAS9191EB MAS, MAS9191EB Datasheet - Page 4

• Manufacturer Part Number: MAS9191EB
• Description: EVALUATION BOARD
• Manufacturer: MAS

FUNCTIONS
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.
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.
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.
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.
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.
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
Battery Charging
MAS9129 Regulators
Microphone Interface
Earphone Interface
Buzzer Interface
Side Tone Circuit
be controlled by changing the values of components
R11, R12,C43 and C44.
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.
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.
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.
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.
The DAC connector contains a direct interface to the
three MAS9191A internal 8-bit DACs.
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.
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
J3 connects DAC1 to V
of the VCTCXO can be measured through jumper
CM5.
RX and TX Interfaces
Microphone and Rx Audio Level Measurement
Test Points
CTRL Interface
Three 8-bit DAC Outputs
MAS9191A Serial Bus Interface
MS8323 Output Frequency
CONT
. The current consumption
DA9191EB.006
June 30,1997
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