CH1794A Cermetek Microelectronics, CH1794A Datasheet - Page 9

• Manufacturer Part Number: CH1794A
• Manufacturer: Cermetek Microelectronics

Specifications of CH1794A

• Lead Free Status / RoHS Status: Not Compliant

Cermetek Microelectronics, Inc.
NOTE:
2007 Cermetek Microelectronics, Inc.
PIN
10
11
12
13
14
15
16
17
18
19
20
21
22
1
2
3
4
5
6
7
8
9
NAME
RING
GND
RXD
DSR
DCD
VCC
SPK
TXD
DTR
CTS
RST
RTS
OHI
(1) If VCC has a slow power up ramp time, the internal reset may be ineffective.
(2) Do not drive LED’s directly from any output. Use Buffers.
TIP
NC
NC
NC
NC
NC
NC
NC
T1
RI
TYPE
I/O
I/O
I/O
O
O
O
O
O
O
O
-
-
-
-
-
I
-
I
-
-
-
I
I
TELCO/TELSET INPUT. Directly connects to the telephone line’s RING lead through a
user supplied RJ-11C jack.
TELCO/TELSET INPUT. Directly connects to the telephone line’s TIP lead through a
user supplied RJ-11C jack.
ANALOG VOICE INJECT. Input (See Figure 5). 2.2V P-P max. Let float if not used.
No Connection.
SPEAKER. Audio output for speaker. See speaker control schematic in Figure 5.
No Connection.
No Connection.
No Connection.
No Connection.
TRANSMIT DATA. Active Low. Serial Transmit data input. Marking or a binary 1
condition is transmitted when a HIGH is asserted.
RECEIVE DATA. Active Low. Serial Receive data output. Received marking or binary
1 condition is indicated by HIGH.
No Connection.
DATA TERMINAL READY. Active LOW. Switching off DTR can either return modem
to command state, disconnect phone call, or reset modem. DTR should be set LOW
when not used.
DATA SET READY. LOW indicates handshaking with a remote modem is in progress,
and/or the data carrier of a remote modem has been detected. Commands &S0 or &S1
must be executed to active to this pin.
RING INDICATION. Active Low. This signal follows the frequency of the ringing signal
and is normally about 20 to 40 Hz for 2 seconds on with 4 seconds off. This pin is also
used for Zero Power option. See Figure 3.
CLEAR-TO SEND. Active LOW. Indicates that the modem is ready to accept data from
the DTE. Used for hardware Flow Control of data.
DATA CARRIER DETECT.
modem has been detected. Must be enabled using the &C1 command.
No Connection.
OFF-HOOK INDICATION. Active HIGH. Indicates when HS Modem goes off-hook.
ONLY present on “H” version products. See Figure 2.
POWER SUPPLY. 5 volts + 5% or 3.3 volts + 5%.: Noise should be less than 25mV
peak to peak.
GROUND. Note: Noise should be less than 25mV peak to peak.
RESET. Active HIGH. This input must be asserted HIGH for at least 10 ms to reset the
modem. RESET is then returned LOW for normal operation. If no system reset is
available, let this pin float let this pin float to enable the internal reset. Input impedance
of driving circuit should be <10K.
REQUEST TO SEND. Active LOW. Used for flow control. Should be tied low if not
used.
Table 3.
HS Modem Family Pin Descriptions.
Page 9
Active LOW.
FUNCTION
CH179XA/2056A High Speed Family of Ultra Small Modems
Indicates a data carrier from a remote
Document No. 607-0020 Revision B (01/07)