CH1794A Cermetek Microelectronics, CH1794A Datasheet - Page 4

• Manufacturer Part Number: CH1794A
• Manufacturer: Cermetek Microelectronics

Specifications of CH1794A

• Lead Free Status / RoHS Status: Not Compliant

Cermetek Microelectronics, Inc.
Speaker Interface.
receiver analog input and provides a signal that can be
used to monitor call progress. The SPK signal can
drive a 300-ohm load directly.
signal is input into an audio power amplifier and the
amplifier, in turn, drives the speaker coil. The speaker
is activated with the ATMn command. The speaker
volume is adjusted using the ATLn command; where n
is 0, 1, 2, or 3. Increasing numbers correspond to
higher volume.
driving an external 8-ohm speaker.
Sleep Mode. To minimize power consumption, the
HS Family of Modems includes a power reduction
feature called Sleep Mode. When activated, the HS
Family of Modems will automatically enter Sleep Mode
after 1 to 255 seconds of inactivity.
delay is selected using the S24 register. The S24 is
set to default to 0 by the factory which disables this
feature. The HS Family of Modems returns to normal
operation when a ring signal is received or upon an
input low signal on the TXD pin.
power is reduced to about 1/3 of normal operating
power.
Zero Power Mode. The “P” versions of the HS Family
of Modems support Zero Power Mode operation. If an
application calls for zero power during standby
periods, this feature allows the power to the HS
Modem to be switched off using external circuitry and
then reapplied when the modem’s RI pin becomes
active. The HS Modem can thus be powered down to
zero current.
Referring to Figure 3, the controller activates the relay
switch, supplying power (+5V) to the HS Modem. In
this configuration, the ring signal is used to “wake up”
the HS Modem when the HS Modem is in the zero
power state.
The user supplies an external pull-up resistor
(Cermetek recommends 30k ohms) to an active 5V
source to limit the current drawn by the when the HS
Modem is in zero power mode. An internal blocking
diode provides supply isolation.
The pins of the HS Modem will be in an undefined
state when powered is switched off.
taken into consideration to assure that no unwanted
signals are presented to the HS Modem during zero
power operation.
Power Supply. The HS Modem module is a complex
set of sensitive subsystems.
normal operation, the HS Modem decodes analog
signals from the telephone line that are in the millivolt
range. Steps must be taken by the user to guarantee
that power supply noise on all supply lines, including
ground, does not exceed 25mV peak to peak.
necessary, use dedicated power and ground planes.
2007 Cermetek Microelectronics, Inc.
Figure 3 indicates one method of
The SPK output reflects the
During the course of
Typically, the SPK
In Sleep Mode,
This must be
The inactivity
If
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Failure to provide such operating conditions could
cause the HS Modem to malfunction or to function
erratically.
The HS Modem family requires +5V ±5% supply. It is
recommended that bypass capacitors be placed on the
power supply as close to the HS Modem’s supply input
pins as practical. It is recommended that a 10 µF or
greater tantalum capacitor in parallel with a 0.1 µF
ceramic capacitor be used.
provide shielding from nearby sources of EMI, such as
relays, motors and other power supplies.
Automatic Speed/Format Sensing. The HS Modem
supports
operation.
Figure 3. Example of Zero Power Operation.
The HS Modem can automatically determine the
speed and format of the data sent from the DTE over
the serial interface; and can sense the following broad
range of speeds:
CH1794A
CH1799A
CH2056A
The data formats in Table 1 are recognized by the HS
Modem family of products. The HS Modem can sense
data with mark or space parity and configures itself as
described in Table 2.
CH179XA/2056A High Speed Family of Ultra Small Modems
both Command and Data modes of
300, 600, 1200, 2400, 4800, 7200,
9600, 12000, 14400, 19200, 38400, and
57600bps.
300, 600, 1200, 2400, 4800, 7200,
9600, 12000, 14400, 16800, 19200,
21600, 24000, 26400, 28800, 38400,
57600, and 115200bps.
300, 600, 1200, 2400, 4800, 7200,
9600, 12000, 14400, 16800, 19200,
21600, 24000, 26400, 28800, 38400,
57600, 115200, and 230400bps.
Document No. 607-0020 Revision B (01/07)
30K
The user must also