MT88E39

CMOS MT88E39 Calling Number Identification Circuit Advance Information (CNIC1.1) Features • • 1200 baud Bell 202 and CCITT V.23 Frequency Shift Keying (FSK) demodulation Compatible with Bellcore GR-30-CORE, SR-TSV-002476, TIA/EIA-716 and ETSI 300 778-1 High input sensitivity Dual mode 3-wire data interface (Serial FSK data stream or MT88E43 compatible 1 byte buffer) Internal gain adjustable amplifier Carrier detect status output Uses 3.579545 MHz crystal or ceramic resonator 3 to 5V ±10% supply voltage Low power CMOS with power down mode Direct pin to pin replacement of MT8841 and MT88E41 DS5035 ISSUE 3 November 1998 Ordering Information MT88E39AS 16 Pin SOIC -40 to +85 °C • • Description The MT88E39 Calling Number Identification Circuit (CNIC1.1) is a CMOS integrated circuit which provides an interface to calling line information delivery services that utilize 1200 baud Bell 202 or CCITT V.23 FSK data transmission schemes. The MT88E39 receives and demodulates the FSK signal and outputs the data into a simple dual mode 3-wire serial interface which eliminates the need for an UART. The MT88E39 is Bellcore, ETSI and NTT compatible and can operate in 3V and 5V applications. It is a pin to pin replacement of the MT8841 and MT88E41 by operating in the MT88E41 FSK interface mode (mode 0) when placed in a MT88E41 socket. New designs may also choose the MT88E43 compatible interface (mode 1) where the microcontroller reads the FSK byte from a 1 byte buffer. • • • • • • Applications • Global (North America, Japan, Europe) FSK based CID (Calling Identity Delivery) / CLIP (Calling Line Identity Presentation) Feature phones, adjunct boxes FAX machines Telephone answering machines Computer Telephony Integration (CTI) Battery powered applications • • • • • GS ININ+ + Receive Bandpass Filter FSK Demodulator Data and Timing Recovery DATA DR DCLK CAP VRef Bias Generator Carrier Detector CD Clock Generator to other circuits PWDN OSC1 OSC2 VSS VDD MODE IC Figure 1 - Functional Block Diagram 5-1 MT88E39 Advance Information IN+ INGS VRef CAP OSC1 OSC2 VSS 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 16 PIN SOIC VDD IC** MODE* PWDN CD DR DATA DCLK * Was IC1 in MT88E41 ** Was IC2 in MT88E41 Figure 2 - Pin Connections Pin Description Pin # 1 2 3 4 5 6 7 8 9 Name IN+ INGS VRef CAP Non-inverting Op-Amp (Input). Inverting Op-Amp (Input). Gain Select (Output). Gives access to op-amp output for connection of feedback resistor. Voltage Reference (Output). Nominally VDD/2. This is used to bias the op-amp inputs. Capacitor. Connect a 0.1µF capacitor to VSS. Description OSC1 Oscillator (Input). Crystal connection. This pin can be driven directly from an external clocking source. OSC2 Oscillator (Output). Crystal connection. When OSC1 is driven by an external clock, this pin should be left open. VSS Power supply ground. DCLK 3-wire FSK Interface: Data Clock (CMOS Output/Schmitt Input). In mode 0 (MT88E41 compatible mode - when the MODE 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 MODE pin is logic high) this is a Schmitt trigger input used to shift the FSK data byte out to the DATA pin. DATA 3-wire FSK Interface: Data (CMOS Output). In mode 0 (MT88E41 compatible mode - when the MODE pin is logic low) the FSK serial bit stream is output to DATA as demodulated. Mark frequency corresponds to logical 1. Space frequency corresponds to logical 0. In mode 1 (when the MODE pin is logic high) the start and stop bits are stripped off and only the data byte is stored in a 1 byte buffer. At the end of each word signalled by the DR pin, the microcontroller should shift the byte out to DATA pin by applying 8 read pulses at the DCLK pin. 3-wire FSK Interface: Data Ready (Open Drain/CMOS Output). Active low. In mode 0 (MT88E41 compatible mode - when the MODE pin is logic low) this is an open drain output. In mode 1 (when the MODE pin is logic high) this is a CMOS output. This pin denotes the end of a word. Typically, DR is used to interrupt the microcontroller. It is normally hi-Z or high (modes 0 and 1 respectively) and goes low for half a bit time at the end of a word. But in mode 1 if DCLK begins during DR low, the first rising edge of the DCLK input will return DR to high. This feature allows an interrupt requested by DR to be cleared upon reading the first DATA bit. Carrier Detect (Open Drain/CMOS Output). Active low. In mode 0 (MT88E41 compatible mode - when the MODE pin is logic low) this is an open drain output. In mode 1 (when the MODE pin is logic high) this is a CMOS output. A logic low indicates that a carrier has been present for a specified time on the line. A time hysteresis is provided to allow for momentary discontinuity of carrier. The demodulated FSK data is inhibited until the carrier has been detected. 10 11 DR 12 CD 13 PWDN Power Down (Schmitt Input). Active high. Powers down the device including the input op-amp and the oscillator. Must be low for operation. 5-2 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 VDD 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 (VRef) which is used to bias the inputs at VDD/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 MT88E39 Mode 0 C1 R1 IN+ INC2 R4 R5 GS R3 R2 Advance Information This mode is selected when the MODE pin is low. It is the MT88E41 compatible mode where the FSK data stream is output as demodulated. Since the MODE pin was IC1 in MT88E41 and connected to Vss, the MT88E39 will work in mode 0 when placed in a MT88E41 socket. In this mode, the MT88E39 receives the FSK signal, demodulates it, and outputs the data directly to the DATA pin (see Figure 11). For each received stop and start bit sequence, the MT88E39 outputs a fixed frequency clock string of 8 pulses at the DCLK pin. Each DCLK rising edge occurs in the nominal centre of a data bit. DCLK is not generated for the stop and start bits. Consequently, DCLK will clock only valid data into a peripheral device such as a serial to parallel shift register or a microcontroller. The MT88E39 also outputs an end of word pulse (Data Ready) on the DR pin, which indicates the reception of every 10-bit word (counting the start and stop bits) sent from the end office. DR can be used to interrupt a microcontroller or cause a serial to parallel converter to parallel load its data into a microcontroller. The mode 0 DATA pin can also be connected to a personal computer’s serial communication port after converting from CMOS to RS-232 voltage levels. Mode 1 This mode is selected when the MODE pin is high. In this mode, the microcontroller supplies read pulses at the DCLK pin (which is now an input) to shift the 8-bit data words out of the MT88E39, onto the DATA pin. The MT88E39 asserts DR to denote the word boundary and indicate to the microprocessor that a new word has become available (see Figure 12). Internal to the MT88E39, the demodulated data bits are sampled and stored. The start and stop bits are stripped off. After the 8th bit, the data byte is parallel loaded into an 8 bit shift register and DR goes low. The shift register’s contents are shifted out to the DATA pin on the supplied DCLK’s rising edge in the order they were received. If DCLK begins while DR is low, DR will return to high upon the first DCLK. This feature allows the associated interrupt to be cleared by the first read pulse. Otherwise DR is low for half a nominal bit time (1/2400 sec). After the last bit has been read, additional DCLKs are ignored. Note that in both modes, the 3-pin interface may also output data generated by speech or other voiceband VRef DIFFERENTIAL INPUT AMPLIFIER MT88E39 C1 = C2 R1 = R4 R3 = (R2 x R5) / (R2 + R5) For unity gain, R5 = R1 INPUT IMPEDANCE VOLTAGE GAIN (AVdiff) = R5/R1 (ZINdiff) = 2 R12 + (1/ωC)2 Figure 3 - Differential Input Configuration IN+ C RIN IN- RF GS VOLTAGE GAIN (AV) = RF / RIN VRef MT88E39 Figure 4 - Single-Ended Input Configuration 3-wire FSK Data Interface The MT88E39 provides a powerful dual mode 3-wire interface so that the 8-bit data words in the demodulated FSK bit stream can be extracted without the need either for an external UART or for the microcontroller to perform the UART function in software. The interface is specifically designed for the 1200 baud rate and is comprised of the DATA, DCLK (data clock) and DR (data ready) pins. Two modes (0 and 1) are selectable via control of the device’s MODE pin. In mode 0 the FSK bit stream is output as demodulated. In mode 1 the FSK data byte is store in a 1 byte buffer. Note that in mode 0 DR and CD are open drain outputs; in mode 1 they are CMOS outputs. DCLK is an output in mode 0, an input in mode 1. 5-4 Advance Information signals. The user may choose to ignore these outputs when FSK data is not expected, or force the MT88E39 into its power down mode. Power Down Mode For applications requiring reduced power consumption, the MT88E39 can be forced into power down when it is not needed. This is done by pulling the PWDN pin high. In power down mode, the oscillator, op-amp and internal circuitry are all disabled and the MT88E39 will not react to the input signal. DR and CD are at high impedance or at logic high (modes 0 and 1 respectively). In mode 0, DATA and DCLK are at logic high. The MT88E39 can be awakened for reception of the FSK signal by pulling the PWDN pin low. Carrier Detect The carrier detector provides an indication of the presence of a signal in the FSK frequency band. It detects the presence of a signal of sufficient amplitude at the output of the FSK bandpass filter. The signal is qualified by a digital algorithm before the CD output is set low to indicate carrier detection. A 10ms hysteresis is provided to allow for momentary signal drop out once CD has been activated. CD is released when there is no activity at the FSK bandpass filter output for 10 ms. When CD is inactive (high), the raw output of the demodulator is ignored by the data timing recovery circuit (see Figure 1). In mode 0, the DATA pin is forced high. No DCLK or DR signal is generated. In mode 1, the internal shift register is not updated and no DR is generated. If DCLK is clocked (in mode 1), DATA is undefined. Note that signals such as CAS, speech and DTMF tones also lie in the FSK frequency band and the carrier detector may be activated by these signals. They will be demodulated and presented as data. To avoid false data, the PWDN pin should be used to disable the FSK demodulator when no FSK signal is expected. Ringing, on the other hand, does not pose a problem as it is ignored by the carrier detector. Crystal Oscillator The MT88E39 uses either a 3.579545MHz ceramic resonator or crystal oscillator as the master timing source. The crystal specification is as Frequency: Frequency tolerance: Resonance mode: Load capacitance: Maximum series resistance: Maximum drive level (mW): e.g. CTS MP036S MT88E39 follows: 3.579545 MHz ±0.2%(-40°C+85°C) Parallel 18 pF 150 ohms 2 mW MT88E39 OSC1 OSC2 MT88E39 OSC1 OSC2 MT88E39 OSC1 OSC2 3.579545 MHz to the next MT88E39 (For 5V application only) Figure 5 - Common Crystal Connection For 5V applications any number of MT88E39 devices can be connected as shown in Figure 5 such that only one crystal is required. The connection between OSC2 and OSC1 can be DC coupled as shown, or the OSC1 input on all devices can be driven from a CMOS buffer (dc coupled) with the OSC2 outputs left unconnected. VRef a nd CAP Inputs VRef is the output of a low impedance voltage source equal to VDD/2 and is used to bias the input op-amp. A 0.1µF capacitor is required between CAP and VSS to suppress noise on VRef. Applications Table 1 shows the Bellcore and ETSI FSK signal characteristics. The application circuit in Figure 6 will meet these requirements. For 5V designs the input op-amp should be set to unity gain to meet the Bellcore requirements and -2.5 dB gain for ETSI requirements. As supply voltage (VDD) is decreased, the FSK detect threshold will be lowered. Therefore for designs operating at other than 5V nominal voltage, to meet the FSK reject level requirement the gain of the op-amp should be reduced accordingly. For 3V designs the gain settings for Bellcore and ETSI should be -3dB and -5.5dB respectively. 5-5 MT88E39 For applications requiring detection of lower FSK signal level, the input op-amp may be configured to provide adequate gain. However, too much gain will cause noise tolerance to fail the TIA requirements because the FSK signal will be clipped at GS when the single tone noise is added. Advance Information Vdd TIP Vdd R2 MT88E39 IN+ VDD IC MODE PWDN CD DR DATA DCLK R8*1 R9*1 Vdd 100nF 20% C1 R1 D1 D2 Vdd Vdd RING C2 R3 D3 D4 R4 R5 R6 R7 INGS VRef CAP 100nF 20% D5 D7 D6 D8 1N5231B OSC1 Xtal OSC2 VSS 100nF 10% 50V (FSK interface mode 0 selected) Vdd = To microcontroller = From microcontroller 200K 5% Motorola 4N25 464K 5% (Ring Detect) 10nF To microcontroller 330nF R10 10% 250V Note: *1 R8 and R9 not required when FSK interface mode 1 is selected. Unless stated otherwise, resistors are 1%, 0.1 Watt; capacitors are 5%, 6.3V D1, D2, D3, D4 = diodes, 1N4003 or 1N4148 or equivalent D5, D6, D7, D8 = bridge rectifier diodes, 1N914 Xtal = 3.579545 MHz, +/-0.2% R8 = R9 = 100K, 20% R10 = 12K1, 1W5, 5%, Fusible resistor R2 = R4 = 34K For 1000Vrms, 60Hz isolation from Tip to Earth and Ring to Earth: R1 = R3 = 430K, 0.5W, 5%, 475V minimum. e.g. IRC Type GS-3 C1 = C2 = 2n2, 1332V minimum If the 1000Vrms is met by other means, then this circuit has to meet FCC part 68 Type B Ringing: R1 = R3 = 432K, 0.1W, 1%, 56V minimum C1 = C2 = 2n2, 212V minimum Example of component values for Vdd = 5V +/- 10% For Bellcore applications, set input gain = 0dB: R5 = 53K6 R6 = 60K4 R7 = 464K Example of component values for Vdd = 3V +/- 10% For Bellcore applications, set input gain = -3 dB: R5 = 44K2 R6 = 51K1 R7 = 332K For ETSI applications, set input gain = -2.5dB: R5 = 53K6 R6 = 63K4 R7 = 348K For ETSI applications, set input gain = -5.5dB: R5 = 44K2 R6 = 53K6 R7 = 249K Figure 6 - Application Circuit 5-6 Advance Information MT88E39 North America: Bellcore *1 1200 Hz +/- 1% 2200 Hz +/- 1% -36.20 to -4.23 dBm *3 (12 to 476 mVrms) -48.23 dBm (3 mVrms) (VMWI only) 1200 baud +/- 1% -6 to +10 dB Single tone (f): -18 dB (f