MT88E45BS

MT88E45B 4-Wire Calling Number Identification Circuit 2 (4-Wire CNIC2) Features • Compatible with: • Bellcore GR-30-CORE, SR-TSV-002476, ANSI/TIA/EIA-716, TIA/EIA-777; • ETSI ETS 300 778-1 (FSK only variant) & -2; • BT (British Telecom) SIN227 & SIN242 Bellcore ‘CPE Alerting Signal’ (CAS), ETSI ‘Dual Tone Alerting Signal’ (DT-AS), BT Idle State and Loop State ‘Tone Alert Signal’ detection 1200 baud Bell 202 and CCITT V.23 FSK demodulation Separate differential input amplifiers with adjustable gain for Tip/Ring and telephone hybrid or speech IC connections Selectable 3-wire FSK data interface (bit stream or 1 byte buffer) Facility to monitor the stop bit for framing error check FSK Carrier detect status output 3 to 5V +/- 10% supply voltage Uses 3.579545MHz crystal or ceramic resonator Low power CMOS with power down Bellcore CID (Calling Identity Delivery) and CIDCW (Calling Identity Delivery on Call Waiting) telephones and adjuncts ETSI, BT CLIP (Calling Line Identity Presentation) and CLIP with Call Waiting telephones and adjuncts Fax and answering machines Computer Telephony Integration (CTI) systems FSKen+Tip/Ring CASen IN1+ IN1GS1 IN2+ IN2GS2 VREF Bias Generator PWDN Oscillator + Hybrid CASen MODE FSKen PWDN CASen May 2003 O rdering Information MT88E45BS 20 Pin SOIC MT88E45BN 20 Pin SSOP -40°C to 85°C • Description The MT88E45B is a low power CMOS integrated circuit suitable for receiving the physical layer signals used in North American (Bellcore) Calling Identity Delivery on Call Waiting (CIDCW) and Calling Identity Delivery (CID) services. It is also suitable for ETSI and BT Calling Line Identity Presentation (CLIP) and CLIP with Call Waiting services. The MT88E45B contains a 1200 baud Bell 202/ CCITT V.23 FSK demodulator and a CAS/DT-AS detector. Two input op-amps allow the MT88E45B to be connected to both Tip/Ring and the telephone hybrid or speech IC receive pair for optimal CIDCW telephone architectural implementation. FSK demodulation is always on Tip/Ring, while CAS detection can be on Tip/Ring or Hybrid Receive. Tip/ Ring CAS detection is required for the Bellcore/TIA Multiple Extension Interworking (MEI) and BT’s onhook CLIP. A selectable FSK data interface allows the data to be processed as a bit stream or extracted from a 1 byte on chip buffer. Power management has been incorporated to power down the FSK or CAS section when not required. Full chip power down is also available. The MT88E45B is suitable for applications using a fixed power source (with a +/10% variation) between 3 and 5V. MODE • • • • • • • • • Applications • • • + PWDN PWDN Anti-Alias Filter PWDN FSK Bandpass FSKen CASen 2130Hz Bandpass 2750Hz Bandpass FSK Demodulator Data Timing Recovery DATA DCLK CD Mux Carrier Detector DR STD DR/STD Tone Detection Algorithm Guard Time ST/GT EST Vdd Vss Control Bit Decode CASen CB0 CB1 CB2 OSC1 OSC2 F igure 1 - Functional Block Diagram 1 MT88E45B VREF IN1+ IN1GS1 Vss OSC1 OSC2 CB0 DCLK DATA 1 2 3 4 5 6 7 8 9 10 MT88E45B 20 19 18 17 16 15 14 13 12 11 IN2+ IN2GS2 CB2 CB1 Vdd CD ST/GT EST DR/STD Data Sheet Figure 2 - Pin Connections Pin Description Pin # Name 1 2 3 4 VREF IN1+ IN1GS1 Description Voltage Reference (Output). Nominally Vdd/2. It is used to bias the Tip/Ring and Hybrid input opamps. Tip/Ring Op-amp Non-inverting (Input). Tip/Ring Op-amp Inverting (Input). Tip/Ring Gain Select (Output). This is the output of the Tip/Ring connection op-amp. The opamp should be used to connect the MT88E45B 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 (which is always on Tip/Ring) or CAS detection (for MEI or BT on-hook CLIP) of the GS1 signal is enabled via the CB1 and CB2 pins. See Tables 1 and 2. Power supply ground. 5 6 7 8 Vss OSC1 Oscillator (Input). Crystal connection. This pin can also be driven directly from an external clock source. OSC2 Oscillator (Output). Crystal connection. When OSC1 is driven by an external clock, this pin should be left open. CB0 Control Bit 0 (CMOS 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. 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. The FSK interface is consisted of the DATA, DCLK and DR/STD pins. See the 3 pin descriptions to understand how CB0 affects the FSK interface. When CB0 is high and CB1, CB2 are both low the MT88E45B is put into a power down state consuming minimal power supply current. See Tables 1 and 2. 9 DCLK 3-wire FSK Interface Data Clock (Schmitt Input/CMOS Output). In mode 0 (when the CB0 pin is logic low) this is a CMOS output which denotes the nominal mid-point of a FSK data bit. In mode 1 (when the CB0 pin is logic high) this is a Schmitt trigger input used to shift the FSK data byte out to the DATA pin. 2 Data Sheet Pin Description Pin # Name 10 DATA Description MT88E45B 3-wire FSK Interface Data (CMOS Output). Mark frequency corresponds to logical 1. Space frequency corresponds to logical 0. In mode 0 (when the CB0 pin is logic low) the FSK serial bit stream is output to the DATA pin directly. In 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 signalled by the DR/STD pin, the microcontroller should shift the byte out onto the DATA pin by applying 8 read pulses to the DCLK pin. A 9th DCLK pulse will shift out the stop bit for framing error checking. 11 DR/STD 3-wire FSK Interface Data Ready/CAS Detection Delayed Steering (CMOS Output). Active low. When FSK demodulation is enabled via the CB1 and CB2 pins this pin is the Data Ready output. It denotes the end of a word. In both FSK interface modes 0 and 1, it is normally hi and goes low for half a bit time at the end of a word. But in mode 1 if DCLK starts during DR 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. When CAS detection is enabled via the CB1 and CB2 pins this pin is the Delayed Steering output. It goes low to indicate that a time qualified CAS has been detected. EST CAS Detection Early Steering (CMOS Output). Active high. This pin is the raw CAS detection output. It goes high to indicate the presence of a signal meeting the CAS accept frequencies and signal level. It is used in conjunction with the ST/GT pin and external components to time qualify the detection to determine whether the signal is a real CAS. 12 13 ST/GT CAS Detection Steering/Guard Time (CMOS Output/Analog Input). It is used in conjunction with the EST pin and external components to time qualify the detection to determine whether the signal is a real CAS. A voltage greater than VTGt at this pin causes the MT88E45B to indicate that a CAS has been detected by asserting the DR/STD pin low. A voltage less than VTGt frees up the MT88E45B to accept a new CAS and returns DR/STD to high. CD Carrier Detect (CMOS Output). Active low. A logic low indicates that an FSK signal is present. A time hysteresis is provided to allow for momentary signal discontinuity. The demodulated FSK data is ignored by the MT88E45B until carrier detect has been activated. Positive power supply. Control Bit 1 (CMOS Input). Together with CB2 this pin selects the MT88E45B’s functionality between FSK demodulation, Tip/Ring CAS detection and Hybrid CAS detection. When CB0 is high and CB1, CB2 are both low the MT88E45B is put into a power down state consuming minimal power supply current. See Tables 1 and 2. Control Bit 2 (CMOS Input). Together with CB1 this pin selects the MT88E45B’s functionality between FSK demodulation, Tip/Ring CAS detection and Hybrid CAS detection. When CB0 is high and CB1, CB2 are both low the MT88E45B is put into a power down state consuming minimal power supply current. See Tables 1 and 2. Hybrid Gain Select (Output). This is the output of the hybrid receive connection op-amp. The opamp should be used to connect the MT88E45B to the telephone hybrid or speech IC receive pair. The hybrid receive signal can be amplified or attenuated at GS2 via selection of the feedback resistor between GS2 and IN2-. When the CPE is off-hook CAS detection of the GS2 signal should be enabled via the CB1 and CB2 pins. See Tables 1 and 2. Hybrid Op-amp Inverting (Input). Hybrid Op-amp Non-Inverting (Input). 14 15 16 Vdd CB1 17 CB2 18 GS2 19 20 IN2IN2+ 3 MT88E45B CB0 CB1 CB2 0/1 0/1 0/1 1 1 0 1 0 1 FSK Interface Function Data Sheet Set by CB0 FSK Demodulation. Tip/Ring input (GS1) selected. DR/STD is DR. Set by CB0 Hybrid CAS Detection. Hybrid Receive input (GS2) selected. DR/STD is STD. Set by CB0 Tip/Ring CAS Detection. Tip/Ring input (GS1) selected. DR/STD is STD. When the line is off-hook, a Bellcore/TIA Multiple Extension Interworking (MEI) compatible Type 2 CPE should be able to detect CAS from Tip/Ring while the CPE is on-hook because it may be the ACK sender. Tip/Ring CAS detection is also required for BT’s on-hook CLIP. Mode 1 Mode 0 Power Down. The MT88E45B is disabled and draws virtually no power supply current. Reserved for factory testing. 1 0 0 0 0 0 Table 1 - CB0/1/2 Functionality The number of control bits (CB) required to interface the MT88E45B with the microcontroller depends on the functionality of the application, as shown in Table 2. Functionality Group FSK (mode 0 or 1) and Hybrid CAS only (Non MEI compatible) Control s CB2 Description CB0 is hardwired to Vdd or Vss to select the FSK interface. CB1 hardwired to Vdd. The microcontroller uses CB2 to select between the 2 functions. CB0 is hardwired to Vdd or Vss to select the FSK interface. The microcontroller uses CB1 and CB2 to select between the 3 functions. CB0 is hardwired to Vdd to select FSK interface mode 1. The microcontroller uses CB1 and CB2 to select between the 4 functions. FSK (mode 0 or 1), Hybrid CAS, Tip/Ring CAS (MEI compatible or BT on-hook CLIP) FSK (mode 1), Hybrid CAS, Tip/Ring CAS, Power Down (MEI compatible or BT on-hook CLIP) FSK (mode 0), Hybrid CAS, Tip/Ring CAS, Power Down (MEI compatible or BT on-hook CLIP) CB1 CB2 CB1 CB2 CB0 CB1 CB2 All 3 pins are required. Table 2 - Control Bit Functionality Groups Functional Overview The MT88E45B is compatible with FSK and FSK plus CAS (CPE Alerting Signal) based Caller ID services around the world. Caller ID is the generic name for a group of services offered by telephone operating companies whereby information about the calling party is delivered to the subscriber. In Europe and some other countries Caller ID is known as Calling Line Identity Presentation (CLIP). ETSI calls CAS ‘Dual Tone Alerting Signal’ (DT-AS), BT calls it ‘Tone Alert Signal’. Depending on the service, data delivery can occur when the line is in the on-hook or off-hook state. In most countries the data is modulated in either Bell 4 202 or CCITT V.23 FSK format and transmitted at 1200 baud from the serving end office to the subscriber’s terminal. Additionally in off-hook signalling, the special dual tone CAS is used to alert the terminal before FSK data transmission. BT uses CAS to alert the terminal prior to FSK in both onhook (Idle State) and off-hook (Loop State) signalling. 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 Data Sheet Message Waiting Indicator) and CIDCW (Calling Identity Delivery on Call Waiting). In Europe, Caller ID requirements are defined by ETSI. The CPE documents are ETS 300 778-1 for on-hook, ETS 300 778-2 for off-hook. The end office requirements are ETS 300 659-1 (on-hook) and ETS 300 659-2 (off-hook). ETSI has defined services such as CLIP and CLIP with Call Waiting which are similar to those of Bellcore. Some European countries produce their own national specifications. For example, in the UK BT’s standards are SIN227 and SIN242, the UK CCA (Cable Communications Association) standard is TW/P&E/312. In on-hook Caller ID, such as CND, CNAM and CLIP, the information is typically transmitted (in FSK) 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. In BT’s on-hook CLIP, the signalling begins with a line polarity reversal, followed by CAS and then FSK. Bellcore calls an on-hook capable Caller ID CPE a ‘Type 1 CPE’. In off-hook Caller ID, such as CIDCW and CLIP with Call Waiting, information about a new calling party is sent to the subscriber who is already engaged in a call. Bellcore’s method uses CAS to alert the CPE. When the CPE detects CAS and there are no offhook extensions, the CPE should mute its transmission path and send an acknowledgment to the end office via a DTMF digit called ACK. Upon receiving ACK, the end office will send the FSK data. Bellcore calls an off-hook capable CPE a ‘Type 2 CPE’. A Type 2 CPE is capable of off-hook and Type 1 functionalities and should ACK with a DTMF ‘D’. The ETSI and BT off-hook signalling protocols are similar to Bellcore’s but with timing and signal parametric differences. ETSI has no requirement for off-hook extension checking before ACK. One factor affecting the quality of the CIDCW service is the CPE’s CAS speech immunity. Although the end office has muted the far end party before and after it sends CAS, the near end (the end which is to receive the information) user may be still talking. Therefore the CPE must be able to detect CAS successfully in the presence of near end speech. This is called the talkdown immunity. The CPE must also be immune to imitation of CAS by speech from both ends of the connection because the CAS detector is continuously exposed to speech throughout the call. This is called the talkoff immunity. MT88E45B If the CPE is a telephone, one way to achieve good CAS speech immunity is to put CAS detection on the telephone hybrid or speech IC receive pair instead of on Tip and Ring. Talkdown immunity improves because the near end speech has been attenuated while the CAS level is the same as on Tip/Ring, resulting in improved signal to speech ratio. Talkoff immunity is also improved because the near end speech has been attenuated. In the Bellcore SR-TSV-002476 Issue 1 off-hook protocol, the CPE should not ACK if it detected an off-hook extension. The FSK will not be sent and the customer will not receive the Call Waiting ID. Bellcore, together with the TIA (Telecommunications Industry Association) TR41.3.1 working group, has defined a CPE capability called Multiple Extension Interworking (MEI) which overcomes this problem. In the MEI scheme, all MEI compatible CPEs must be capable of detecting CAS when the line is offhook, even though the CPE itself may be on-hook. This is because under some conditions an on-hook CPE may become the ACK sender. Another reason for the on-hook CPE to detect CAS is to maintain synchronous call logs between on and off-hook CPEs. When CAS is received and all off-hook CPEs are MEI compatible, one of the CPEs will ACK and all compatible CPEs will receive FSK. A problem arises in a CPE where the CAS detector is connected only to the hybrid or speech IC receive pair: it cannot detect CAS when it is on-hook. The reason is that when the CPE is on-hook either the hybrid/speech IC is non functional or the signal level is severely attenuated. Therefore an on-hook Type 2 CPE must be capable of detecting CAS from Tip/ Ring, in addition to detecting CAS from the hybrid/ speech IC receive signal when it is off-hook. The MT88E45B offers an optimal solution which combines good speech immunity and MEI compatibility. Two input op-amps allow the MT88E45B to be connected both to Tip/Ring and to the hybrid/speech IC receive pair. Both connections can be differential or single ended. FSK demodulation is always on the Tip/Ring signal. CAS detection can be from the Tip/Ring or hybrid/speech IC receive signal. Being able to detect CAS on Tip/ Ring also makes the MT88E45B suitable for BT onhook CLIP applications. For applications such as those in most European countries where Tip/Ring CAS detection is not needed, then the Tip/Ring and Hybrid op-amp gains can be tailored independently to meet country specific FSK and CAS signal level requirements 5 MT88E45B respectively. Note that since the Hybrid op-amp is for CAS detection only, its gain can always be tailored specifically for the CAS signal level. The FSK demodulator is compatible with Bellcore, ETSI and BT standards. The demodulated FSK data is either output directly (bit stream mode) or stored in a one byte buffer (buffer mode). In the buffer mode, the stop bit immediately following a byte is also stored and can be shifted out after the data byte. This facility allows for framing error checking required in Type 2 CPEs. In the bit stream mode, two timing signals are provided. One indicates the bit sampling instants of the data byte, the other the end of byte. A carrier detector indicates presence of signal and shuts off the data stream when there is no signal. The entire chip can be put into a virtually zero current power down mode. The input op-amps, FSK demodulator, CAS detector and the oscillator are all shut off. Furthermore, power management has been incorporated to minimize operating current. When FSK is selected the CAS detector is powered down. When CAS is selected the FSK demodulator is powered down. Data Sheet The feedback resistor connected between GS1 and IN1- can be used to adjust the Tip/Ring signal gain. The feedback resistor connected between GS2 and IN2- can be used to adjust the hybrid receive signal gain. When the Tip/Ring op-amp is selected, the GS2 signal is ignored. When the Hybrid op-amp is selected, the GS1 signal is ignored. Either or both op-amps can be configured in the single ended input configuration shown in Figure 3, or in the differential input configuration shown in Figure 4. IN+ C RIN IN- Voltage Gain (AV) = RF / RIN Highpass Corner Frequency f-3dB = 1/(2πRINC) RF GS VREF Figure 3 - Single Ended Input Configuration F unctional Description 3 to 5V Operation The MT88E45B’s FSK and CAS reject levels are proportional to Vdd. When operated at Vdd equal 3V +/- 10%, to keep the FSK and CAS reject levels as at 5V (nominal) the Tip/Ring and Hybrid op-amp gains should be reduced from those of 5V. Gains for nominal Vdd (with a +/- 10% variation) other than 3 or 5V can be chosen as interpolation between the 3 and 5V settings. I nput Configuration The MT88E45B provides an input arrangement comprised of two op-amps and a bias source (VREF). VREF is a low impedance voltage source which is used to bias the op-amp inputs at Vdd/2. The Tip/ Ring op-amp (IN1+, IN1-, GS1 pins) is for connecting to Tip and Ring. The Hybrid op-amp (IN2+, IN2-, GS2 pins) is for connecting to the telephone hybrid or speech IC receive pair. Either FSK or CAS detection can be selected for the Tip/Ring connection, while the hybrid connection is for CAS detection only. Phrased in another way, FSK demodulation is always on Tip/Ring, while CAS detection can be on Tip/Ring or Hybrid Receive. Tip/ Ring CAS detection is required for MEI and BT onhook CLIP, while Hybrid CAS detection is needed for optimal CAS speech immunity. 6 C1 R1 IN+ IN- C2 R4 R5 GS R3 R2 Differential Input Amplifier C1 = C2 R1 = R4 (For unity gain R5= R4) R3 = (R2R5) / (R2 + R5) Voltage Gain Highpass Corner Frequency (AVdiff) = R5/R1 f-3dB = 1/(2πR1C1) Input Impedance (ZINdiff) = 2 R12 + (1/ωC)2 VREF Figure 4 - Differential Input Configuration CAS Detection In North America, CAS is used in off-hook signalling only. In Europe (ETSI) it is used in off-hook signalling, and by BT in both on and off-hook signalling. ETSI calls it the Dual Tone Alerting Signal (DT-AS). Although the ETSI on-hook standard contains a DT-AS specification, BT is the only administration known to employ CAS in on-hook signalling. (BT calls it Tone Alert Signal.) The CAS/ DT-AS characteristics are summarized in Table 3. Data Sheet 2130 Hz and 2750 Hz CAS/DT-AS Characteristics Frequency Tolerance Signal Level (per tone) Reject Level (per tone) Maximum Twist (V2130Hz/V2750Hz) Duration Reject Duration Signal to Noise Ratio Speech Speech Bellcorea (Off-hook only) +/-0.5% -14 to -32 dBmd -45 dBm +/-6 dB 75 to 85 ms +/-6 dB 75 to 85 ms ETSIb (Off-hook) +/-0.5% -9.78 to -32.78 dBm (-12 to -35 dBVe) MT88E45B BTc (Off-hook = ‘Loop State’) (On-hook = ‘Idle State’) Off-hook: +/-0.6% On-hook: +/-1.1% +0.22 to -37.78 dBm (-2 to -40 dBV) On-hook: -43.78 dBm (-46 dBV) +/-7 dB Off-hook: 80 to 85 ms On-hook: 88 to 110 ms Off-hook: