53ꢀꢁ'ꢂꢃ53ꢄꢄꢁ'ꢂꢃDQGꢃ53ꢅꢆꢆ'
/RZꢃ9ROWDJHꢃ9ꢇꢈꢉꢊ.ꢀꢁIOH[ꢊ9ꢇꢄꢆꢊ9ꢇꢄꢋELVꢃ0RGHPꢃ'DWDꢃ3XPSV
Label
I/O Type
Signal Name/Description
TELEPHONE LINE/TELEPHONE/AUDIO INTERFACE SIGNALS AND REFERENCE VOLTAGE
TXA1, TXA2
O(DF)
Transmit Analog 1 and 2 Output. The TXA1 and TXA2 outputs are differential outputs 180 degrees out of
phase with each other. Each output can drive a 300 Ω load. Typically, TXA1 and TXA2 are connected to the
telephone line interface or an optional external hybrid circuit.
RIN
I(DA)
IA
Receive Analog Input. RIN is a single-ended input with 70K Ω input impedance. Typically, RIN is connected to
telephone line interface or an optional external hybrid circuit.
NOTE: If not used, do not tie directly to ground; this input has a bias voltage of +2.5V (VAA = +5V).
RINGD
Ring Detect. The RINGD input is monitored for pulses in the range of 15 Hz to 68 Hz. The frequency detection
range may be changed by the host in DSP RAM. The circuit driving RINGD should be a 4N35 optoisolator or
equivalent. The circuit driving RINGD should not respond to momentary bursts of ringing less than 125 ms in
duration, or less than 40 VRMS (15 Hz to 68 Hz) across TIP and RING. Detected ring signals are reflected on
the ~RI output signal as well as the RI bit.
~RLYA
OD
Relay A Control. The ~RLYA open drain output can directly drive a reed relay coil with a minimum resistance of
360 ohms (9.2 mA max. @ +3.3V). A clamp diode, such as a 1N4148, should be installed across the relay coil.
An external transistor can be used to drive heavier loads (e.g., electro-mechanical relays). ~RLYA is controlled
by host setting/resetting of the RA bit.
(~OHRC,
~CALLID)
In a typical application, ~RLYA is connected to the normally open Off-Hook relay (~OHRC). In this case, ~RLYA
active closes the relay to connect the MDP to the telephone line.
Alternatively, in a typical application, ~RLYA is connected to the normally open Caller ID relay (~CALLID). When
the MDP detects a Calling Number Delivery (CND) message, the ~RLYA output is asserted to close the Caller ID
relay in order to AC couple the CND information to the MDP RIN input (without closing the off-hook relay and
allowing loop current flow which would indicate an off-hook condition).
~RLYB
OD
Relay B Control. The ~RLYB open drain output can directly drive a reed relay coil with a minimum resistance of
360 ohms (9.2 mA max. @ 3.3V). A clamp diode, such as a 1N4148, should be installed across the relay coil. An
external transistor can be used to drive heavier loads (e.g., electro-mechanical relays). ~RLYB is controlled by
host setting/resetting of the RB bit.
(~TALK)
In a typical application, ~RLYB is connected to the normally closed Talk/Data relay (~TALK). In this case,
~RLYB active opens the relay to disconnect the handset from the telephone line.
MICM
SPK
I(DA)
Modem Microphone Input. MICM is a single-ended microphone input. The input impedance is > 70k Ω.
NOTE: If not used, do not tie directly to ground; this input has a bias voltage of +2.5V (VAA = +5V).
O(DF)
Speaker Analog Output. The SPK analog output can originate from one of five different sources: RIN, TELIN,
MICM or MICV or from the MDP’s internal voice playback mode. The SPK on/off and three levels of attenuation
are controlled by bits in DSP RAM. When the speaker is turned off, the SPK output is clamped to the voltage at
the VC pin. The SPK output can drive an impedance as low as 300 ohms. In a typical application, the SPK
output is an input to an external LM386 audio power amplifier.
SPKMD
VREF
OA
Modem Speaker Digital Output. The SPKMD digital output reflects the received analog input signal digitized to
TTL high or low level by an internal comparator to create a PC Card (PCMCIA)-compatible signal.
REF
REF
I(DA)
High Voltage Reference. Connect to VC through 10 µF (polarized, + terminal to VREF) and 0.1 µF (ceramic) in
parallel.
VC
Low Voltage Reference. Connect to a ferrite bead and connect the other end of the ferrite bead to DGND
through 10 µF (polarized, + terminal to VC) and 0.1 µF (ceramic) in parallel.
MICV/NC*
Voice Microphone Input. MICV is a single-ended microphone input. Typically, MICV is connected to a
microphone output for recording voice e.g., in a speakerphone application.
NOTE: If not used, do not tie directly to ground; this input has a bias voltage of +2.5V (VAA = +5V).
TELIN/NC*
I(DA)
Telephone Analog Input. TELIN is a single-ended input with 70K Ω input impedance. Typically, TELIN is
connected to a telephone handset microphone circuit.
NOTE: If not used, do not tie directly to ground; this input has a bias voltage of +2.5V (VAA = +5V).
TELOUT/NC* O(DF)
Telephone Analog Output. TELOUT is a single-ended output that can drive a 300 Ω load. Typically, TELOUT is
connected to a telephone handset speaker circuit.
MICBIAS
REF
Microphone Bias. Microphone bias reference voltage.
CONEXANT [ CONEXANT SYSTEMS, INC ]
