MT88E46
Bellcore Compliant Calling Number
Identification Circuit
Data Sheet
Features
•
•
•
•
Compatible with Bellcore GR-30-CORE,
SR-
TSV-002476; TIA/EIA-716 and TIA/EIA-777
Pin compatible with MT88E45
Differential input amplifiers with adjustable gains
for Tip/Ring and 4-wire side connections
TIA (Telecommunications Industry Association)
MEI (Multiple Extension Interworking) compatible
architecture: CAS (CPE Alerting Signal) detection
is selectable between Tip/Ring and 4-wire side
4-wire side CAS detection is Bellcore talkoff and
talkdown compliant when near end speech is
attenuated 8 dB or better, and is close to talkoff
compliant even without near end speech attenuation
Tip/Ring side CAS detection typically meets
talkdown condition 1 (the average case)
1200 baud Bell 202 and CCITT V.23 FSK
demodulation
Selectable 3-wire FSK data interface (serial bit
stream or 1 byte buffer) with facility to monitor stop
bit for framing error check
FSK carrier detect status output
3 to 5 V
±
10% supply voltage
Uses 3.579545 MHz crystal
Low power CMOS with power down mode
Ordering Information
MT88E46AS
MT88E46ASR
MT88E46AS1
MT88E46ASR1
20 Pin SOIC
20 Pin SOIC
20 Pin SOIC*
20 Pin SOIC*
*Pb Free Matte Tin
-40 to +85
°C
Tubes
Tape & Reel
Tubes, Bake &
Drypack
Tape & Reel,
Bake & Drypack
November 2006
•
Computer Telephony Integrated (CTI) systems
•
Description
The MT88E46 is a CMOS integrated circuit suitable for
receiving the FSK and CAS signals in North American
(Bellcore) CIDCW, CWD and CID (Calling Identity
Delivery) services. It provides an optimal solution for the
CIDCW (also known as Type 2) and CWD (Type 2.5)
telephone set applications by providing separate input op-
amps for Tip/Ring and 4-wire side (receive pair of the
telephone hybrid or speech IC) connections. The Tip/Ring
connection is compatible with TIA’s MEI scheme and can
be used for FSK demodulation and ‘on hook mode’ CAS
detection. The 4-wire side connection is for ‘off hook
mode’ CAS detection. The CAS detection modes - on
hook and off hook - use different algorithms which are
optimized for the CPE states. In ‘off hook mode’ the CAS
detector is Bellcore compliant when near end speech is
attenuated 8dB or better. ‘On hook mode’ is optimized for
talkdown only and typically meets talkdown condition 1
(the average case) without speech attenuation at Tip/Ring
such as in the on hook state MEI CPE.
•
•
•
•
•
•
•
Applications
•
Bellcore compliant CIDCW (Calling Identity
Delivery on Call Waiting) and CWD (Call Waiting
Deluxe) telephones
CIDCW and CWD telephone adjunct boxes
•
GS1
IN1+
IN1-
IN2+
IN2-
GS2
V
REF
Bias
Generator
+
-
PWDN
+
-
GS1en
FSK
Bandpass
GS1en
Anti-Alias
Filter
PWDN
PWDN
MODE
GS1en
FSKen
CASen
Control Bit
Decode
2130Hz
Bandpass
2750Hz
Bandpass
CASen
On/Off Hook mode
Tone
Detection
Algorithm
FSKen
CASen
Carrier
Detector
FSK
Demod
MODE
Data Timing
Recovery
DATA
DCLK
CD
Mux
DR
DET
DR/DET
PWDN
Oscillator
Vdd
Vss
OSC1
OSC2
CB0 CB1 CB2
Patent pending
Figure 1 - Functional Block Diagram
Zarlink Semiconductor Inc.
Zarlink, ZL and the Zarlink Semiconductor logo are trademarks of Zarlink Semiconductor Inc.
Copyright 2000-2006, Zarlink Semiconductor Inc. All Rights Reserved.
MT88E46
Change Summary
Changes from March 2000 Issue to November 2006 Issue.
Page
1
Item
Change
Updated Ordering Information.
Data Sheet
V
REF
IN1+
IN1-
GS1
Vss
OSC1
OSC2
CB0
DCLK
DATA
1
2
3
4
5
6
7
8
9
10
MT88E46
20
19
18
17
16
15
14
13
12
11
IN2+
IN2-
GS2
CB2
CB1
Vdd
CD
NC
IC
DR/DET
Figure 2 - Pin Connections
Pin Description
Pin #
1
2
3
Name
V
REF
IN1+
IN1-
Description
Voltage Reference (Output).
Nominally Vdd/2. It is used to bias the GS1 (Tip/Ring connection) and
GS2 (telephone hybrid or speech IC receive pair connection) input op-amps.
GS1 Op-Amp Non-inverting Input.
The op-amp is for connecting the MT88E46 to Tip/Ring.
GS1 Op-Amp Inverting Input.
The op-amp is for connecting the MT88E46 to Tip/Ring.
Gain Select 1 (Output).
This is the output of the GS1 op-amp. The op-amp should be used to connect the
MT88E46 to Tip and Ring. The Tip/Ring signal can be amplified or attenuated at GS1 via selection of the
feedback resistor between GS1 and IN1-.
FSK demodulation or ‘on hook mode’ CAS detection of the GS1 signal can be selected via the CB1 and
CB2 pins. See Tables 1 and 2.
5
6
7
Vss
OSC1
OSC2
Power Supply Ground.
Oscillator Input.
Crystal connection. This pin can also be driven directly from an external clock source.
Oscillator Output.
Crystal connection. When OSC1 is driven by an external clock, this pin should be left
open circuit.
Control Bit 0 (CMOS Logic Input).
This pin is used primarily to select the 3-wire FSK data interface
mode. When it is low, interface mode 0 is selected where the FSK bit stream is output directly at the
DATA pin. When it is high, interface mode 1 is selected where the FSK byte is stored in a 1 byte buffer
which can be read serially by the application’s microcontroller.
8
CB0
The FSK interface is consisted of the DATA, DCLK and DR/DET pins. See the 3 pin descriptions to
understand how CB0 affects the FSK interface.
This pin is also used with CB1 and CB2 to put the MT88E46 into a power down state drawing virtually
no power supply current. See Tables 1 and 2.
4
GS1
2
Data Sheet
Pin Description
Pin #
Name
Description
MT88E46
9
DCLK
3-Wire FSK Interface Data Clock (Schmitt Logic Input/CMOS Logic Output).
In interface mode 0
(when the CB0 pin is logic low) this is a CMOS output whose rising edge denotes the nominal mid-point
of a bit in the FSK data byte.
In interface mode 1 (when the CB0 pin is logic high) this is a Schmitt trigger input used to shift the FSK
data byte out of an on chip buffer to the DATA pin.
3-Wire FSK Interface Data (CMOS Logic Output).
Mark frequency corresponds to logical 1. Space
frequency corresponds to logical 0.
In interface mode 0 (when the CB0 pin is logic low) the FSK serial bit stream is output to DATA directly.
10
DATA
In interface mode 1 (when the CB0 pin is logic high) the start bit is stripped off, the data byte and the
trailing stop bit are stored in a 9 bit buffer. At the end of each word indicated by the DR signal at the DR/
DET pin, the microcontroller should shift the byte out to DATA by applying 8 read pulses to the DCLK
pin. A 9th DCLK pulse will shift out the trailing stop bit for framing error checking.
3-Wire FSK Interface Data Ready/CAS Detect (CMOS Logic Output).
Active low.
This is a dual purpose pin which indicates the end of an FSK word or the end of CAS.
11
Data Ready:
When FSK demodulation is enabled this pin denotes the end of a word. In both FSK
interface modes 0 and 1, it is normally high and goes low for half a bit time at the end of a word. In mode
DR/DET
1 if DCLK starts while DR is low, the first rising edge of the DCLK input will return DR to high. This
feature allows an interrupt requested by a low going DR to be cleared upon reading the first DATA bit.
CAS Detect:
When CAS detection is enabled, this pin goes low after the end of CAS for 416
µs
(nominal) to indicate that CAS has been detected.
12
13
14
IC
NC
CD
Internal Connection.
Must be left open circuit.
No Connection.
This pin is not bonded to the die and is unaffected by external connections.
Carrier Detect (CMOS Logic Output).
Active low.
A logic low indicates that an FSK signal is present. A 10 ms time hysteresis has been provided to allow
for momentary signal discontinuity. The demodulated FSK data is ignored until carrier detect has been
activated.
Positive Power Supply.
A decoupling capacitor should be connected directly across the Vdd and Vss
pins.
Control Bit 1 (CMOS Logic Input).
Together with CB2 this pin enables FSK demodulation or CAS
detection. See Tables 1 and 2.
Control Bit 2 (CMOS Logic Input).
Together with CB1 this pin enables FSK demodulation or CAS
detection. See Tables 1 and 2.
Gain Select 2 (Output).
This is the output of the GS2 op-amp. The op-amp should be used to connect the
MT88E46 to the receive pair of the telephone hybrid or speech IC. The signal can be amplified or
attenuated at GS2 via selection of the feedback resistor between GS2 and IN2-.
15
16
17
Vdd
CB1
CB2
18
GS2
When the application is a telephone adjunct box where there is no hybrid or speech IC, if the GS2 gain
with respect to Tip/Ring is to be set to the same as that of GS1, the GS2 op-amp can be connected as a
voltage follower to the GS1 op-amp output (see Figure 5).
The GS2 signal is used for ‘off hook mode’ CAS detection only as selected via the CB1 and CB2 pins.
See Tables 1 and 2.
19
20
IN2-
IN2+
GS2 Op-Amp Inverting Input.
The op-amp is for connecting the MT88E46 to the receive pair of the
telephone hybrid or speech IC.
GS2 Op-Amp Non-Inverting Input.
The op-amp is for connecting the MT88E46 to the receive pair of
the telephone hybrid or speech IC.
3
MT88E46
Control Bit (CB0/1/2) Functionality
CB0 CB1 CB2
0/1
0/1
1
1
1
0
FSK
Interface
Set by CB0
Set by CB0
Input
Op-Amp
GS1
GS2
Function
FSK Demodulation.
DR/DET pin is the DR signal.
Data Sheet
‘Off hook mode’ CAS Detection.
DR/DET pin is the DET signal.
The off hook mode algorithm is Bellcore talkoff and talkdown compliant when
near end speech level is attenuated 8 dB or better. It should be used for the off
hook state CPE.
‘On hook mode’ CAS Detection.
DR/DET pin is the DET signal.
When the line is in use, a TIA Multiple Extension Interworking (MEI)
compatible Type 2 CPE must be able to detect CAS even though the CPE itself is
on hook. Since in most telephone designs the hybrid or speech IC is not
operational when the CPE itself is on hook, this mode provides Tip Ring CAS
detection for the on hook state MEI CPE.
The on hook mode algorithm is optimized for talkdown only and typically meets
talkdown condition 1 (the average case) without near end speech attenuation. It
must not be used when the CPE itself is off hook. See ‘On Hook Mode CAS
Detection’ section in ‘Functional Description’.
0/1
0
1
Set by CB0
GS1
1
0
0
0
0
0
Mode 1
Mode 0
-
-
Power Down.
DR/DET pin is logic high.
The MT88E46 is disabled and draws virtually no power supply current. Note that
the DCLK pin becomes an input pin because FSK interface mode 1 is selected by
CB0=1.
Reserved for factory testing.
Table 1 - CB0/1/2 Function Table
The number of control bits (CB) required to interface the MT88E46 to the microcontroller depends on the functionality of
the application.
Functionality Group
FSK,
Off Hook mode CAS
(Non MEI compatible)
FSK,
Off Hook mode CAS,
On Hook mode CAS
FSK (Interface mode 1),
Off Hook mode CAS,
On Hook mode CAS,
Power Down
FSK (Interface mode 0),
Off Hook mode CAS,
On Hook mode CAS,
Power Down
Controls
CB2
CB1
CB2
CB1
CB2
CB0
CB1
CB2
Description
CB0 is connected to Vdd or Vss to select the FSK interface mode.
CB1 connected to Vdd.
The microcontroller uses CB2 to select between the 2 functions.
CB0 is connected to Vdd or Vss to select the FSK interface mode.
The microcontroller uses CB1 and CB2 to select between the 3 functions.
CB0 is connected to Vdd to select FSK interface mode 1.
The microcontroller uses CB1 and CB2 to select between the 4 functions.
All 3 pins are required.
Table 2 -Control Bit Functionality Groups
4
Data Sheet
Functional Overview
In the Calling Identity Delivery on Call Waiting (CIDCW)
and Call Waiting Deluxe (CWD) services offered by
North American telephone operating companies, a dual
tone known as CAS (CPE Alerting Signal) is sent from
the central office to notify the near end CPE, which is
already engaged in an established call, that the central
office wishes to deliver calling identity information of a
waited call. The signalling protocol is specified in
Bellcore GR-30-CORE, the CPE (Customer Premises
Equipment) requirements in SR-TSV-002476.
In the GR-30-CORE off hook protocol, the central office
mutes the far end connection (the other end of the
established call) just before CAS is transmitted. When the
near end CPE detects the CAS, it mutes the handset and
checks whether there is any parallel off hook CPE. If there
is no parallel off hook CPE, it acknowledges CAS
reception by sending ACK, which is a predefined DTMF
digit, back to the central office. When the central office
receives ACK, it transmits the calling party information in
1200 baud Bell 202 format FSK to the near end CPE
which then typically displays the information to the user.
When CAS is transmitted from the central office, even
though the far end has been muted the near end user (the
end which is to receive the caller ID information) may be
speaking. Therefore, the CAS must be detected in the
presence of near end speech, noise or music. Failure to
detect the CAS and reply with ACK within a defined
interval is known as ‘talkdown’. Talkdown is undesirable
because the central office will not deliver the calling
information, hence the quality of the CIDCW or CWD
service will be degraded.
Since CAS can be transmitted anytime during an
established call, the CAS detector is therefore subjected to
speech, noise or music - which can imitate CAS - from
both the near end and the far end throughout the call.
False detection followed by ACK is known as ‘talkoff’.
Talkoff is undesirable because it annoys the far end user
by the near end CPE’s sending ACK and because the near
end CPE is muted in anticipation of the FSK signal.
Bellcore has specified talkdown and talkoff immunity
performance requirements in SR-TSV-002476. If the CPE
is a telephone, one way to achieve good CAS speech
immunity is to put CAS detection on the receive pair of
the telephone hybrid or speech IC instead of on Tip and
Ring. Compared to a Tip/Ring connection, talkdown
immunity improves because the near end speech is
attenuated on the hybrid / speech IC receive pair while the
CAS level is the same as on Tip/Ring. Talkoff immunity is
also better because the near end speech is attenuated.
MT88E46
In the GR-30-CORE issue 1 off hook protocol, the near
end CPE must not ACK if there is a parallel off hook
CPE. Otherwise the ACK will not be detected reliably at
the central office. This restriction is modified by a
protocol known as MEI (Multiple Extension
Interworking)
developed
by
the
TIA
(Telecommunications
Industry
Association)
in
conjunction with Bellcore. MEI allows a CPE to ACK if
all off hook CPEs are MEI compatible. MEI is described
in the TIA/EIA-777 standard.
MEI introduces the concept of the ACK-Sender and the
Backup ACK-Sender.
• On a per call basis, the ACK-Sender is the first CPE
to go off hook for the call. It retains its status even if
it returned on hook while the line remains in use.
The ACK-Sender must give up its status if a Type 3
(Analog Display Services Interface) CPE asserts its
ACK-Sender status.
•
The Backup ACK-Sender is the CPE to last respond
to CAS with an ACK and successfully received FSK
data. It retains its status from call to call but must
give up its Backup ACK-Sender status when another
CPE successfully completes the CAS-ACK-FSK
sequence.
When CAS is sent from the central office, all MEI
compatible off hook CPEs detect CAS and go back on
hook. After the ACK-Sender detected CAS, it monitors
the line voltage. When the line voltage has returned to the
HIGH state (the voltage when the line is not terminated by
any CPE), it goes off hook and sends the ACK. If there is
no ACK-Sender because the first CPE to go off hook is
not MEI compatible, the Backup ACK-Sender takes over
and sends the ACK. Note that both the ACK-Sender and
the Backup ACK-Sender can be on hook or off hook.
Because it may be the ACK-Sender or Backup ACK-
Sender, an MEI compatible on hook state CPE must be
able to detect CAS when the line is in use. Additionally,
the TIA/EIA-777 standard requires an MEI on hook state
CPE to detect CAS during a call so that it can listen in on
the FSK to keep its call log consistent with the off hook
CPEs. However, a CAS detector connected only to the
hybrid / speech IC cannot detect CAS when the CPE itself
is on hook because either the hybrid / speech IC is not
operational or the signal level is severely attenuated.
Therefore an MEI compatible CPE must be able to detect
CAS from Tip/Ring when the CPE is on hook, and be able
to detect CAS from the hybrid / speech IC when the CPE
is off hook.
The MT88E46 offers an optimal solution which combines
Bellcore compliant speech immunity and MEI
compatibility. Two input op-amps allow the MT88E46 to
be connected to both Tip/Ring and to the receive pair of
the telephone hybrid or speech IC (the 4-wire side). Each
connection can be differential or single ended. FSK
5
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