E2A0030-16-X1 ¡ Semiconductor MSM7715 ¡ Semiconductor This version: Jan. 1998 MSM7715 Previous version: Nov. 1996 Multi-Function Telecommunication LSI GENERAL DESCRIPTION The MSM7715 is a signal transmitting and receiving LSI device for applications such as telemeters. The MSM7715 uses a no-ringing communication mode. Built-in functions includes a 300 bps full-duplex modem complying with ITU-T V.21, a DTMF signal (PB signal) generator and receiver, and a call progress tone (CPT) detector. The answer tone (1650 Hz) generation can be accomplished with the built-in modem. A meter terminal can be configured using this transmitting and receiving device along with the meter, NCU, and controller. FEATURES • 3 V power supply. (Voltage range is 2.5 V to 3.6 V.) • Selectable modes, including DTMF signal sending mode, DTMF signal receiving mode, and V.21 modem answer/originate mode. • For DTMF signal reception, support for normal detection mode or high-speed detection mode. • For call progress tone detection, support for rectangular wave output or detection output. • DTMF signal receiving output, which is in a 3-state mode, is able to be connected externally with the DTMF signal sending 4-bit input. • Analog loopback test and remote digital loopback test supported. • Dedicated pins for modem sending/receiving data, carrier detection, sending request, and call progress tone detection. • Independent external adjustment of the analog signal using the modem signal and DTMF signal. • External adjustment of the carrier detection level. • Internal 3.579545 MHz crystal oscillation circuit. • Power-down mode • Package: 44-pin plastic QFP (QFP44-P-910-0.80-2K) (Product name : MSM7715GS-2K) 1/21 PreLPF + – AIN 2765 Hz BEF DT2 DTMF Receiver DT3 DT4 4 dB SP Smooth AOUT CPT Detector – + * CP * Carrier Detector GAT2 RD FSK Modem MOD * TD * RS Voltage Ref. VR1 CPW CD – + GAT1 DTTIM ¡ Semiconductor BLOCK DIAGRAM DT1 CLK X2 VR2 X1 SGO SG SGC DTMF Generator DTO PON VDD Power ON +3 V 0V 2/21 * MODE1 * MODE2 * MODE3 * ICTA * ICTB * TEN * DTG1 * DTG2 * DTG3 * DTG4 Note) DT1 to DT4 : 3-state outputs * : Input with pull-up resistor MSM7715 GND * Mode Select & Test ¡ Semiconductor MSM7715 DTG3 DTG2 DTG1 GND VR2 VR1 DTO MOD GAT2 GAT1 SGC 44 43 42 41 40 39 38 37 36 35 34 PIN CONFIGURATION (TOP VIEW) 28 NC ICTB 7 27 AOUT DTTIM 8 26 NC MODE1 9 25 NC MODE2 10 24 PON MODE3 11 23 SP 22 6 DT4 ICTA 21 VDD DT3 29 20 5 DT2 CPW 19 NC DT1 30 18 4 CP RS 17 AIN CD 31 16 3 RD TD 15 SGO CLK 32 14 2 NC TEN 13 NC X2 33 12 1 X1 DTG4 44-Pin Plastic QFP NC : No connect pin 3/21 ¡ Semiconductor MSM7715 PIN DESCRIPTION Name Description Pin No. I/O DTG4 1 I* Input for specifying the DTMF code to be sent. TEN 2 I* Input for controlling output of the DTMF signal. (Transmit enable) DTG1 to DTG4 are latched at the falling edge of TEN and the DTMF signal is output when “0” is input. See Fig. 2. TD 3 I* Input for data to be sent to the modem. Input the data string at a speed of 300 bps or lower. RS 4 I* Input for controlling the modem sending output. (Request to send) The sending signal is output when “0” is input. I* Input for selecting the output waveform from the call progress tone detector. When "1" is input, a rectangular wave that is synchronized with the input signal is output from the CP. When "0" is input, presence of detected signal is output from the CP pin. See Fig.3. I* Inputs for testing. Leave them open or connect them to VDD. I* Input pin for controlling the detection timing of the DTMF receiver. When “0” is input, the high-speed detection mode is selected. I* Input for selecting the operation mode. See Table 1. CPW 5 ICTA 6 ICTB 7 DTTIM 8 MODE1 9 MODE2 10 MODE3 11 X1 12 I X2 13 O Input and output connected to the crystal oscillator. See “Oscillation Circuit” in the Functional Description. CLK 15 O 3.579545 MHz clock output RD 16 O Output for serial data received by the modem. It is held in the marked state (“1”) when the carrier detector (CD) does not make detection. CD 17 O Output for the carrier detector. “0” means detection, while “1” means non-detection. CP 18 O Output for call progress tone (CPT) detection. When the CPT is detected, the waveform selected by the CPW pin is output. See Fig. 3. DT1 19 DT2 20 DT3 21 O Outputs for the code of the received DTMF signal. In a mode other than the DTMF receiving mode, these pins are in a high-impedance state. DT4 22 SP 23 O Output for presenting the DTMF signal receiving data. “1” means that the DTMF signal is being received. Latch DT1 to DT4 at the rising edge of SP. See Fig. 1. PON 24 I* Input for controlling power-on. When “1” is input, all lines of this device enter the power down state, and then the operation of each funciton stops and the receiver timer is reset. AOUT 27 O Analog signal output. The DTMF signal or modem sending signal is output. 4/21 ¡ Semiconductor Name MSM7715 Pin No. I/O VDD 29 — Power supply. Supply +2.5V to 3.6V. AIN 31 I Input for the analog receiving signal. SGO 32 O Output for the signal ground voltage. The output voltage is 1/2 VDD. Connect a capacitor of 0.1 mF or more between SGO and GND. SGC 34 — Pin for connecting the capacitor of the signal ground voltage generating circuit. Connect a capacitor of 1 mF or more between SGC and GND. GAT1 35 I Input for the sending output level-adjusting amplifier. GAT2 36 O Output for the sending output level-adjusting amplifier. MOD 37 O Output for the sending modem signal. DTO 38 O Output for the DTMF signal. VR1 39 O Output for the reference voltage generating circuit. The potential difference between VR1 and SGO is approximately +0.75 V. VR2 40 I Input for external adjustment of the modem’s carrier detection level. GND 41 — Ground. DTG1 42 DTG2 43 I* Inputs for specifying the DTMF code to be sent. Data is latched at the falling edge of TEN. DTG3 44 Note: Description Digital inputs that are pulled up internally by a high resistance. 5/21 ¡ Semiconductor MSM7715 ABSOLUTE MAXIMUM RATINGS Parameter Power Supply Voltage Input Voltage Storage Temperature Symbol Condition Rating Unit VDD Ta = 25°C With respect to GND –0.3 to 7 V VI –0.3 to VDD + 0.3 V TSTG — –65 to +150 °C RECOMMENDED OPERATING CONDITIONS Symbol Condition Min. Typ. Max. Unit Power Supply Voltage Parameter VDD — 2.5 3.0 3.6 V Operating Temperature Range Top — °C VIH Input Voltage — VIL Input Clock Frequency X1/X2 Load Capacitance –40 — +85 0.8 VDD — VDD 0 — 0.2 VDD fCLK Against 3.579545 MHz –0.1 — +0.1 % C1, C2 — — 12 — pF SGC Bypass Capacitance C3 — — 1 — SGO Bypass Capacitance C6 — 0.1 — — VDD Bypass Capacitance Crystal V mF C5 — 10 — — Oscillation Frequency — — — 3.579545 — Frequency Deviation — At 25°C ±5°C –100 — +100 Temperature Characteristics — At –40°C to +85°C –50 — +50 Equivalent Series Resistance — — — — 90 W Load Capacitance — — — 16 — pF MHz ppm ELECTRICAL CHARACTERISTICS DC Characteristics (VDD = 2.5 V to 3.6 V, Ta = –40°C to +85°C) Parameter Symbol IDD1 Power Supply Current Input Current *1 IDD2 Condition PON = "0" IDDS PON = "1" IIH VIH = VDD IIL VIL = 0 V VOH1 Output Voltage Notes: *2 VOL1 *2 Min. Typ. Max. Modem mode — 3 6 DTMF mode — 2.4 5 Power-down — 1 20 –10 — 10 –50 –10 10 IOH = –100 mA VDD – 0.1 — VDD IOL = 100 mA 0 — 0.1 VOH2 CLK IOH = –100 mA 0.9 VDD — VDD VOL2 CL£10 pF IOL = 100 mA 0 — 0.1 VDD Unit mA mA V *1 The following pins have an internal pull-up resistor. : DTG1 to DTG4, TEN, TD, RS, CPW, ICTA, ICTB, DTTIM, MODE1 to MODE3, and PON *2 RD, CD, CP, DT1 to DT4, and SP 6/21 ¡ Semiconductor MSM7715 AC Characteristics (DTMF) (VDD = 2.5 V to 3.6 V, Ta = –40°C to +85°C) Parameter Transmit Level Transmit Signal Level Relative Value Transmit Frequency Deviation Transmit Signal Distortion Rate Symbol VDTTL VDTTH VDTDF fDDT THDDT Condition Min. Typ. Max. Unit Low-group tone –16.5 –14.5 –12.5 dBm High-group tone –15.5 –13.5 –11.5 *1 0 1 2 dB –1.5 — +1.5 % Harmonics/Fundamental frequency — — –23 dB AOUT, R1 = R3 High-group tone/low-group tone With respect to the nominal frequency DTG1 to DTG4 Input Data Setup Time tSDT See Fig. 2. 250 — — DTG1 to DTG4 Input Data Hold Time tHDT See Fig. 2. 250 — — ns Receive Detect Level VDETDT For each single tone –46 — –10 dBm Receive Reject Level VREJDT For each single tone — — –60 *1 Receive Frequency Detect Band fDETDT With respect to the nominal frequency — — ±1.5 Receive Frequency Reject Band fREJDT With respect to the nominal frequency Allowable Receive Level Difference VTWIST Allowable Receive Noise Level ratio Dial Tone Reject Ratio Signal Repetition Time Tone Time for Detect Tone Time for No Detect Output Delay Time Interdigit Pause Time Acceptable Drop Out Time SP Delay Time Output Trailing Edge Delay Time % VN/S VREJ400 ±3.8 — — High-group tone/low-group tone –6 — +6 Noise (0.3 kHz to 3.4 kHz) level/tone level — –12 — 380 Hz to 420 Hz 37 — — tC1 DTTIM = "1" 120 — — tC2 DTTIM = "0" 70 — — DTTIM = "1" 49 — — DTTIM = "0" 34 — — tI1 DTTIM = "1" — — 24 tI2 DTTIM = "0" — — 9 tS1 tS2 See Fig. 1 tG11 Normal DTTIM = "1" 30 45 57 tG12 condition *2 DTTIM = "0" 20 32 42 tG21 Just after DTTIM = "1" 30 48 77 tG22 mode change *3 DTTIM = "0" 20 35 62 tP1 DTTIM = "1" 30 — — tP2 DTTIM = "0" 21 — — tB1 DTTIM = "1" — — 10 tB2 DTTIM = "0" — — 3 tSP1 DTTIM = "1" 6 8 10 DTTIM = "0" 1 1.7 3 tD1 tS > 80 ms DTTIM = "1" 21 29 35 tD2 tS > 44 ms DTTIM = "0" 15 21 27 tSP2 dB ms 7/21 ¡ Semiconductor Note: MSM7715 *1 0 dBm = 0.775 Vrms (For all AC characteristics) *2 "Normal condition" means that a DTMF signal appears after more than 20 ms after setting DTMF receive mode. *3 "Just after mode change" means that there is an input signal when the mode is changed from DTMF transmit mode to DTMF receive mode. If there is an input signal when power is turned on, see "DTMF mode setting procedure after power on or after releasing power down mode". AC Characteristics (Modem) (VDD = 2.5 V to 3.6 V, Ta = –40°C to +85°C) Parameter Symbol Min. Typ. Max. Unit Modem Transmit Level VAOM Measured at AOUT pin, R1 = R2 –11 –9 –7 dBm Signal Level Relative Value VDM Mark signal/space signal dB fOM Modem Transmit Carrier Frequency fOS fAM fAS Transmit Signal Output Deray Condition Originate mode Answer mode –1.5 0 1.5 Mark, TD = "1" 976 980 984 Space, TD = "0" 1176 1180 1184 Mark, TD = "1" 1646 1650 1654 Space, TD = "0" 1846 1850 1854 — 3.5 — –48 *1 — –6 –42 tADD TD Æ AOUT Modem Receive Signal Level VAIM Measured at AIN. FSK modulation signal Carrier Detection (CD) Signal Level VON Answer mode : 1080 Hz OFFÆON — –44 VOFF Originate mode : 1750 Hz ONÆOFF –48 –46 — CD Level Hysteresis VHYS VR2 open at AIN pin — 2 — tCDD1 OFF Æ –6 dBm — 8 — tCDD2 OFF Æ –40 dBm 5 14 22 tCDH1 –6 dBm Æ OFF 20 31 40 tCDH2 –40 dBm Æ OFF — 23 — Time CD Delay Time CD Hold Time Hz ms dBm dB ms Demodulated Data Bias Distortion DBS 300 bps,1 : 1 pattern — — ±10 % NRTS Signal Versus Modem Receive Signal Allowable Level Ratio VNR VNRTS/V receive modem signal NRTS : 2765 Hz ±30 Hz — — –2 dB Receive data output Delay Time tRDD AIN Æ RD — 5 — ms *1 When the carrier detector does not detect (CD="1"), RD is fixed to "1". AC Characteristics (Call progress tone detector) (VDD = 2.5 V to 3.6 V, Ta = –40°C to +85°C) Min. Typ. Max. Unit CPT Detect Level Parameter Symbol VDETCP 400 Hz Condition –40 — –6 dBm CPT Non-Detect Level VREJCP 400 Hz — — –60 dBm CPT Detect Frequency fDETCP See Fig. 3. 380 — 420 Hz 500 — — — — 300 CPT Non-Detect Frequency fREJCP CPT Detect Delay Time tDELCP — — 20 — ms CPT Detect Hold Time tHOLCP — — 15 — ms See Fig. 3. Hz 8/21 ¡ Semiconductor MSM7715 AC Characteristics (VDD = 2.5 V to 3.6 V, Ta = –40°C to +85°C) Parameter Symbol Min. Typ. Max. Unit AOUT — — 1.1 Vp-p MOD, DTO, GAT2 20 — — Resistor between VR1 and SGO 40 — — RLAO AOUT 30 — — ROX AOUT, MOD, DTO, GAT2, VR1, SGO — 100 — W — 10 — MW Transmit Signal Output Level VAOUT Output Load Resistance RLVR1 RLX Output Impedance Input Impedance Output DC Potential Condition RAI GAT1, AIN VSG SGO VDCAO AOUT — VDD/2 — Potential difference between VR1 and SGO 0.7 0.75 0.8 4 kHz to 8 kHz — — –45 Measured at AOUT 8 kHz to 12 kHz — — –65 R1= 30 kW every 4 kHz C4 = 680 pF bandwidth of VREF VS1 VS2 Out-of-band Output Noise VS3 kW VDD/2–0.1 VDD/2 VDD/2+0.1 V dBm — –70 –60 12 kHz or more 9/21 ¡ Semiconductor MSM7715 TIMING DIAGRAM When DTMF is received tC tI tS tP tB AIN signal tG DT1 to 4 SP tD tSP Figure 1 DTMF Receive Timing tS tI tP tB tSP tC tG1n tD : Tone time for detect When the input signal duration is tS or more, receiving is normally done. : Tone time for no detect When the input signal duration is tI or less, this input signal is ignored and DT1 to DT4 and SP is not output. : Interdigit pause time When there is no input signal for tP or more, DT1 to DT4 and SP are reset. : Acceptable drop out time DT1 to DT4 and SP are not reset even though a no-signal state for tB or less (momentary no-signal) occurs during signal receiving. The tB is applicable while the received signals are output. (SP="1") : SP delay time Against the DT1 to DT4 output, SP is output after a delay of tSP. Therefore, latch DT1 to DT4 at the rising edge of SP. : Signal repetition time For normal receiving, set the signal repetition time to tC or more. : Output delay time (n: 1 or 2) Against the appearance of the input signal, DT1 to DT4 are outputs after a delay of tG1n. : Output trailing edge delay time Against the stop of the input signal, DT1 to DT4 and SP stop outputting after a delay of tD. 10/21 ¡ Semiconductor MSM7715 When the DTMF tone is sent TEN tSDT tHDT DTG1 DTG2 DTG3 DTG4 DTO 941 Hz + 1447 Hz Figure 2 DTMF Transmit Timing When the call progress tone (CPT) is detected 400 Hz AIN CP CPW = "1" CP CPW = "0" tDELCP tHOLCP Figure 3 Call Progress Tone Detect Timing 11/21 ¡ Semiconductor MSM7715 FUNCTIONAL DESCRIPTION Oscillation circuit Connect a 3.579545 MHz crystal resonator between X1 and X2. If the load capacitance of the crystal resonator is 16 pF, connect a 12 pF capacitor between X1 and GND and between X2 and GND. When an external clock is used, input the external clock to X2 via a 200 pF capacitor and leave X1 open. C1 X1 X1 C2 X2 X2 3.579545 MHz 3.579545 MHz Figure 4 Connection of the Crystal Resonator Figure 5 Connection of the External Clock Signal ground Connect a capacitor of 1 mF between SGC and GND. Do not connect anything other than this capacitor to the SGC pin. SGO can also be used as the reference voltage for the peripheral circuit. A capacitor of 0.1 mF or more should be connected between SGO and GND. SGC + – C3 SG voltage generating circuit + – SGO To the peripherals To the internal circuit + – C6 Figure 6 Signal Ground Digital input pin The digital input pin contains a pull-up resistor. Therefore, supply the VIH voltage (VDD) to this pin or open this pin to input "1". To input "0", supply the VIL voltage (GND) to this pin. Upon power down (PON = "1"), this pull-up goes into a high-impedance state. Therefore, current is not affected upon power down even though the VIL voltage remains connected to the digital input pin. 12/21 ¡ Semiconductor MSM7715 Operation mode selection By setting the MODE1 to MODE3 pins, an operation mode can be selected (see Table 1). The call progress tone detector (CPT DET.) can be operated in the DTMF signal transmit mode and modem mode. However, since the carrier detector is also used for the call progress tone detector, only rectangular waveform output is available in modem mode. Set CPW = "1" when activating the call progress tone detector in a modem mode. Table 1 Operation Mode Table MODE Functional Block Operation Mode 3 2 1 0 0 0 0 0 1 0 1 0 0 1 1 1 0 1 0 1 1 1 1 0 Modem Analog loopback 1 mode Test (ALB) mode 0 Remote digital loopback (RDLB) 1 DTMF mode DTMF GEN. DTMF signal transmit DTMF FSK REC. MODEM * DTMF signal receive CPT DET. CPW = "1" CPW = "0" * * * Normal Originate (O) operation Answer (A) * * * * O * * A * * O * * A * * * means active. Note: The carrier detecor may malfunction within 40 ms after the operating mode is changed from the DTMF or power down mode to the modem mode. Therefore, ignore an output signal from CD and RD during this period of time. DTMF mode setting procedure after power-on or after releasing power-down mode The following is a recommendable procedure to use DTMF mode after power-on or after releasing power-down mode. (1) Put power-on or release power-down mode. (2) Set DTMF signal transmit mode. PON="0", TEN="1" (3) Wait more than 20 ms, VDD must be more than 2.5 V after this wait time. (4-1) In the case of DTMF receive, set DTMF signal to receive mode. (4-2) In the case of DTMF transmit, it is possible control transmit enable (TEN). Modem mode setting procedure after power-on The following is a recommendable procedure to use Modem mode after power-on. (1) Power on. (2) Set PON="1", TEN="1" and RS="1". Set mode to be used. (3) More than 200 ms after VDD becomes more than 2 V, set PON="0". (4) Wait more than 20 ms. VDD must be more than 2.5 V after this wait time. (5) It is possible to control transmit output. Ignore an output signal from CD and RD of more than 40 ms which includes the wait time of term (4). 13/21 ¡ Semiconductor MSM7715 Modem signal flow Figure 7 shows the signal flow during normal modem operation. AIN Line AOUT Receive filter Demodulator Transmit filter Modulator RD Received data Transmitted data TD Figure 7 Signal Flow in Normal Operation The MSM7715 uses the analog loopback test (ALB) mode and remote digital loopback test (RDLB) mode as the modem testing functions. In these test modes, the signal flow shown in Figure 8 is used. O (originate)/A (answer) in the test mode is the expression based on the modulator side. In ALB mode, the transmit analog signal is input to the demodulator and can be monitored as RD. In RDLB mode, the modem is configured as the remote modem in the RDL test mode. Data from the other modem that requested for RDL is returned to the other modem as a result of echo-back. AIN RD Receive filter Demodulator Transmit filter Modulator Received data [ALB] TD Transmitted data AOUT AIN Receive filter Demodulator Transmit filter Modulator RD Received data [RDLB] AOUT TD Transmitted data Figure 8 Signal Flow in Test Mode 14/21 ¡ Semiconductor MSM7715 DTMF signal code Sixteen types of DTMF transmit signals can be set by using DTG1 to DTG4. Also, sixteen types of DTMF receive signals can be monitored by using DT1 to DT4. Table 2 shows the DTMF signal codes. Table 2 DTMF Signal Codes Button Low-group signal (Hz) 697 1 * 2 * 3 * 770 852 941 * 6 1633 * * * * 7 * 8 * 9 * * * * 0 * * * # D 1477 * * C 1336 * 5 B 1209 * 4 A High-group signal (Hz) * * * * * * * * DT4 DT3 DT2 DT1 DTG4 DTG3 DTG2 DTG1 0 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 0 1 0 1 0 1 1 0 0 1 1 1 1 0 0 0 1 0 0 1 1 0 1 0 1 0 1 1 1 1 0 0 * 1 1 0 1 * 1 1 1 0 * 1 1 1 1 * 0 0 0 0 15/21 ¡ Semiconductor MSM7715 Microcontroller interface By externally connecting DT1 to DT4 and DTG1 to DTG4 respectively, a 4-bit bus can be configured (Fig 9). In DTMF signal transmit mode, DT1 to DT4 enter a high-impedance state and this 4-bit line is used to set the DTMF code against DTG1 to DTG4. The bus data is latched at the falling edge of TEN. In DTMF signal receive mode, DT1 to DT4 enter an output state. The 4-bit bus line is used as the output of the DTMF code from DT1 to DT4 to the microcontroller. Latch this bus data at the rising edge of SP. In modem mode, DT1 to DT4 enter a high-impedance state. This 4-bit bus line is pulled up by the pull-up resistor in DTG1 to DTG4. In power-down mode (PON = "1"), DT1 to DT4 enter a high-impedance state. Since the pull-up resistors in DTG1 to DTG4 also enter a high-impedance state, potential of this 4-bit bus line becomes unstable from the MSM7715. DT1 DT2 Microcontroller DTMF Receiver DT3 DT4 DTG1 DTG2 DTG3 DTMF Generator DTG4 Figure 9 Microcontroller Interface Example 16/21 ¡ Semiconductor MSM7715 Setting the transmit signal level 4dB AOUT VAO + – RC-LPF GAT2 C4 R1 GAT1 R3 R2 DTO MOD DTMF Generator Modulator R1, R2, R3 ≥ 20 kW, R1 £ R2, R1 £ R3 Figure 10 Setting the Transmit Signal Level The modem’s modulated analog signal and DTMF signal are not transmitted at the same time. The signal to be transmitted is determined by the selected operation mode. This device provides the pins for individual setting of transmit signal levels. VAOM: Level of the modem signal at the AOUT pin when R1 = R2 (dBm) VAODT: Level of the DTMF signal at the AOUT pin when R1 = R3 (dBm) When external resistors (R1, R2, R3) are changed, the signal level at AOUT is as follows: VAO (modem) = 20 ¥ log (R1/R2) + VAOM VAO (DTMF) = 20 ¥ log (R1/R3) + VAODT However, to avoid distorted output, R1 ≤ R2 and R1 ≤ R3 are needed. In circuit design, R1 = R2 or R1 = R3 with 5% tolerance is permitted. C4 is a component in the first order LPF for suppressing the out-of-band output noise. Select a value C4 in such a way that cutoff frequency FC determined by R1 and C4 will be approximately 8 kHz. C4 = 1/ (2p ¥ R1 ¥ FC) 17/21 ¡ Semiconductor MSM7715 External adjustment of the carrier detection level 11 R4 12 R5 6 VR1 VR2 SG VREF r1 r2 COMP R4 + R5 ≥ 20 kW r1 : 300 kW, r2 : 600 kW Figure 11 External Adjustment of the Carrier Detection Level The carrier detection level is determined by the resistance ratio between the MSM7715's internal resistors r1 and r2, unless external resistors R4 and R5 are connected. By connecting external resistors R4 and R5, the detection level can be adjusted. However, the width of hysteresis cannot be changed. Ra = R4 ¥ r1/(R4 + r1), Parallel-connected resistance of R4 and r1 Rb = R5 ¥ r2/(R5 + r2), Parallel-connected resistance of R5 and r2 VON = 20 ¥ log (Rb/(Ra + Rb)) –40.5 (dBm) VOFF = 20 ¥ log (Rb/(Ra + Rb)) –42.5 (dBm) Caution: r1 and r2 may vary in similar proportions over a 0.5 to 2.0 ¥ range, due to the lot variation and temperature variation. 18/21 ¡ Semiconductor MSM7715 Analog Interface C7 r4 4 dB Line R8 – + AMP2 600 W : 600 W R10 600 W – + AMP1 r3 C8 R7 AOUT R6 R14 R13 – + C9 AIN – + + – VT VR R9 R15 SGO R11 R12 SG R15≥60 kW Figure 12 Analog Interface Circuit Example When R1 = R2 in the modem mode, the AOUT output level is at its maximum value of about –9 dBm. When R1 = R3 in DTMF mode, the AOUT output level is at its maximum value of –11 dBm (sum of the low group and high group). To increase the transmit output level in the line to a high level, use an external amplifier (AMP1). The receive signal levels can be adjusted by the values of R13 and R14. Clock noise of about –70 dBm will be generated from AOUT as out-of-band noise. (Clock noise has a frequency of 27.965 kHz and its odd harmonics.) The clock noise level is nearly always constant even if the output level of AOUT is lowered by varying the values of resistors R1 to R3 that are connected to GAT1, GAT2, DTO, and MOD. Therefore, to suppress this noise output to the line, build a LPF at the AMP1. Note, however, that setting the cutoff frequency of the LPF too low affects the output signal level. Note that too large a time constant determined by the values of C9 and R15 allows the longer time required for reaching a stable DC level, which may result in the violation of specification for the DTMF signal receive output delay time. Example: R15=100 kW, C9=0.022 mF. Larger circuit-return levels of the transmit signal to the AIN pin can cause receive data errors. If the line impedance is equal to the R10 impedance, R8=R9 can not induce the circuit-return levels of the transmit signal to the AIN pin. The peripheral circuits should be designed so that the circuit-return level, including variations of the line impedance, of the transmit signal to the AIN pin is –9 dBm or less. 19/21 ¡ Semiconductor MSM7715 APPLICATION CIRCUIT SP PON R12 C8 R6 Positive Supply AOUT R1 GAT2 R2 MOD R3 DTO DT4 DT3 DT2 DT1 CP CD RD CLK VR1 X1 GND ICTA ICTB DTTIM MODE1 MODE2 MODE3 C1 CPW DTG1 DTG2 DTG3 C2 X2 VR2 DTG4 TEN TD RS C4 SGC GAT1 VDD C3 SGO AIN C6 –+ C5 R15 C9 – + R7 R14 C7 – + R8 R13 R11 – + R10 R9 Line Microcontroller 20/21 ¡ Semiconductor MSM7715 PACKAGE DIMENSIONS (Unit : mm) QFP44-P-910-0.80-2K Mirror finish Package material Lead frame material Pin treatment Solder plate thickness Epoxy resin 42 alloy Solder plating 5 mm or more Package weight (g) 0.41 TYP. Notes for Mounting the Surface Mount Type Package The SOP, QFP, TSOP, SOJ, QFJ (PLCC), SHP and BGA are surface mount type packages, which are very susceptible to heat in reflow mounting and humidity absorbed in storage. Therefore, before you perform reflow mounting, contact Oki’s responsible sales person for the product name, package name, pin number, package code and desired mounting conditions (reflow method, temperature and times). 21/21