Advance Information
Pin Description
Pin #
14
Name
Description
MT88E39
MODE
Mode select (Input).
This pin selects the 3-wire FSK interface mode. To select mode 0
(MT88E41 compatible mode) this pin should be logic low. To select mode 1 this pin should be
logic high.
Because this pin is already connected to Vss in ’E41 applications, the MT88E39 can replace
the ’E41 without any circuit or software change.
IC
V
DD
Internal Connection.
Internal connection. Leave open circuit. In MT88E41, this was IC2
which was also left open in the application circuit.
Positive power supply voltage.
The MT88E39 provides an interface to the Caller ID
physical layer. It bandpass filters and demodulates
the 1200 baud FSK signal. It also provides a
convenient interface to extract the demodulated FSK
data. Although the main application of the MT88E39
is Caller ID, it can also be used wherever 1200 baud
Bell 202 and/or CCITT V.23 FSK reception is
required.
3 to 5V operation
The MT88E39 can operate from 5.5V down to 2.7V,
but the FSK reject level will change with Vdd. In a
battery powered CPE, the FSK accept level will
become lower as the batteries are run down. If the
CPE is designed for 4.5V, the accept level will be
lowered when the batteries drain to 3V. In North
America there is a requirement for rejecting FSK
signals which are below 3 mVrms when data is not
preceded by ringing, such as VMWI (Visual Message
Waiting Indicator) applications. When the batteries
are drained, the CPE will not meet the reject level.
For on-hook Caller ID, there is no reject level and the
CPE will meet all requirements.
Input Configuration
The input arrangement of the MT88E39 provides an
operational amplifier, as well as a bias source (V
Ref
)
which is used to bias the inputs at V
DD
/2
. Provision is
made for connection of a feedback resistor to the
op-amp output (GS) for adjustment of gain.
Figure 3 shows the necessary connections for a
differential input configuration. In a single-ended
configuration, the input pins are connected as shown
in Figure 4.
15
16
Functional Description
The MT88E39 is a FSK demodulator compatible with
FSK based Caller ID services around the world, such
as in North America, France, Germany, and Japan.
Caller ID is the generic term for a group of services
offered by telephone operating companies whereby
information about the calling party is delivered to the
subscriber. In the FSK based methods, the
information is modulated in either Bell 202 (in North
America) or CCITT V.23 (in Europe) FSK format and
transmitted at 1200 baud from the serving end office
to the subscriber’s terminal.
In North America, Caller ID uses the voiceband data
transmission interface defined in the Bellcore
document GR-30-CORE. The terminal or CPE
(Customer Premises Equipment) requirements are
defined in Bellcore document SR-TSV-002476.
Typical services are CND (Calling Number Delivery),
CNAM (Calling Name Delivery), VMWI (Visual
Message Waiting Indicator) and CIDCW (Calling
Identity Delivery on Call Waiting).
In on-hook Caller ID, such as CND and CNAM, the
information is typically transmitted from the end
office before the subscriber picks up the phone.
There are various methods such as between the first
and second rings (North America), between an
abbreviated ring and the first true ring (Japan,
France and Germany). On-hook Caller ID can also
occur without ringing for services such as VMWI.
The MT88E39 is suitable for these forms of alerting.
In off-hook Caller ID, such as CIDCW, information
about a new calling party is sent to the subscriber
who is already engaged in a call. Bellcore’s method
uses a special dual tone known as CAS (CPE
Alerting Signal) which should be detected by the
CPE. After the CPE has acknowledged with a DTMF
digit, the end office will send the FSK data. The
MT88E39 is suitable for receiving the FSK data but a
separate CAS detector is required.
5-3
MITEL [ MITEL NETWORKS CORPORATION ]
