MSM7715

E2A0030-16-X1 ¡ Semiconductor MSM7715 ¡ Semiconductor Multi-Function Telecommunication LSI This version: Jan. 1998 MSM7715 Previous version: Nov. 1996 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 BLOCK DIAGRAM ¡ Semiconductor DT1 AIN + – 4 dB AOUT – + GAT2 GAT1 – + FSK Modem Voltage Ref. * * Smooth CPT Detector * PreLPF 2765 Hz BEF DT2 DTMF Receiver DT3 DT4 SP DTTIM CP * Carrier Detector CPW CD RD TD RS CLK X2 VR2 SGO SGC DTO PON VDD GND * Power ON +3 V 0V DTMF Generator SG Mode Select & Test * * * * * * * * * * X1 MODE1 MODE2 MODE3 ICTA ICTB TEN DTG1 DTG2 DTG3 DTG4 Note) DT1 to DT4 : 3-state outputs MOD VR1 MSM7715 * : Input with pull-up resistor 2/21 ¡ Semiconductor MSM7715 PIN CONFIGURATION (TOP VIEW) DTG3 DTG2 DTG1 GAT2 GAT1 35 MOD GND SGC 34 DTO 38 VR2 40 VR1 39 44 43 42 41 37 DTG4 TEN TD RS CPW ICTA ICTB DTTIM MODE1 MODE2 MODE3 36 1 2 3 4 5 6 7 8 9 10 11 33 32 31 30 29 28 27 26 25 24 23 NC SGO AIN NC VDD NC AOUT NC NC PON SP 12 13 14 15 16 17 18 19 20 21 DT3 NC RD CLK CD CP DT1 DT2 44-Pin Plastic QFP NC : No connect pin DT4 X1 X2 22 3/21 ¡ Semiconductor MSM7715 PIN DESCRIPTION Name DTG4 TEN Pin No. 1 2 I/O I* I* Description Input for specifying the DTMF code to be sent. 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. Input for data to be sent to the modem. Input the data string at a speed of 300 bps or lower. Input for controlling the modem sending output. (Request to send) The sending signal is output when “0” is input. 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. Inputs for testing. Leave them open or connect them to VDD. Input pin for controlling the detection timing of the DTMF receiver. When “0” is input, the high-speed detection mode is selected. Input for selecting the operation mode. See Table 1. Input and output connected to the crystal oscillator. See “Oscillation Circuit” in the Functional Description. 3.579545 MHz clock output 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. Output for the carrier detector. “0” means detection, while “1” means non-detection. Output for call progress tone (CPT) detection. When the CPT is detected, the waveform selected by the CPW pin is output. See Fig. 3. TD RS 3 4 I* I* CPW 5 I* ICTA ICTB DTTIM MODE1 MODE2 MODE3 X1 X2 CLK RD CD CP DT1 DT2 DT3 DT4 SP 6 7 8 9 10 11 12 13 15 16 17 18 19 20 21 22 23 I* I* I* I O O O O O 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. 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. 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. Analog signal output. The DTMF signal or modem sending signal is output. PON AOUT 24 27 I* O 4/21 ¡ Semiconductor MSM7715 Name VDD AIN SGO SGC GAT1 GAT2 MOD DTO VR1 VR2 GND DTG1 DTG2 DTG3 Pin No. 29 31 32 34 35 36 37 38 39 40 41 42 43 44 I/O — I O — I O O O O I — I* Description Power supply. Supply +2.5V to 3.6V. Input for the analog receiving signal. 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. Pin for connecting the capacitor of the signal ground voltage generating circuit. Connect a capacitor of 1 mF or more between SGC and GND. Input for the sending output level-adjusting amplifier. Output for the sending output level-adjusting amplifier. Output for the sending modem signal. Output for the DTMF signal. Output for the reference voltage generating circuit. The potential difference between VR1 and SGO is approximately +0.75 V. Input for external adjustment of the modem’s carrier detection level. Ground. Inputs for specifying the DTMF code to be sent. Data is latched at the falling edge of TEN. Note: 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 VDD VI TSTG Condition Ta = 25°C With respect to GND — Rating –0.3 to 7 –0.3 to VDD + 0.3 –65 to +150 Unit V V °C RECOMMENDED OPERATING CONDITIONS Parameter Power Supply Voltage Operating Temperature Range Input Voltage Input Clock Frequency X1/X2 Load Capacitance SGC Bypass Capacitance SGO Bypass Capacitance VDD Bypass Capacitance Oscillation Frequency Frequency Deviation Crystal Symbol VDD Top VIH VIL fCLK C1, C2 C3 C6 C5 — — — — — Condition — — — Against 3.579545 MHz — — — — — At 25°C ±5°C At –40°C to +85°C — — Min. 2.5 –40 0.8 VDD 0 –0.1 — — 0.1 10 — –100 –50 — — Typ. 3.0 — — — — 12 1 — — 3.579545 — — — 16 Max. 3.6 +85 VDD 0.2 VDD +0.1 — — — — — +100 +50 90 — Unit V °C V % pF mF MHz ppm Temperature Characteristics Equivalent Series Resistance Load Capacitance W pF ELECTRICAL CHARACTERISTICS DC Characteristics (VDD = 2.5 V to 3.6 V, Ta = –40°C to +85°C) Parameter Power Supply Current Symbol IDD1 IDD2 IDDS Input Current IIH *1 IIL VOH1 Output Voltage VOL1 *2 VOH2 VOL2 CLK CL£10 pF PON = "0" PON = "1" VIH = VDD VIL = 0 V *2 IOH = –100 mA IOL = 100 mA IOH = –100 mA IOL = 100 mA Condition Modem mode DTMF mode Power-down Min. — — — –10 –50 VDD – 0.1 0 0.9 VDD 0 Typ. 3 2.4 1 — –10 — — — — Max. 6 5 20 10 10 VDD 0.1 VDD 0.1 VDD V mA Unit mA Notes: *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 AC Characteristics (DTMF) MSM7715 (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 DTG1 to DTG4 Input Data Setup Time DTG1 to DTG4 Input Data Hold Time Receive Detect Level Receive Reject Level Receive Frequency Detect Band Receive Frequency Reject Band Allowable Receive Level Difference Allowable Receive Noise Level ratio Dial Tone Reject Ratio Signal Repetition Time Tone Time for Detect Tone Time for No Detect Symbol VDTTL VDTTH VDTDF fDDT THDDT tSDT tHDT VDETDT VREJDT fDETDT fREJDT VTWIST VN/S VREJ400 tC1 tC2 tS1 tS2 tI1 tI2 tG11 Output Delay Time tG12 tG21 tG22 Interdigit Pause Time Acceptable Drop Out Time SP Delay Time Output Trailing Edge Delay Time tP1 tP2 tB1 tB2 tSP1 tSP2 tD1 tD2 tS > 80 ms tS > 44 ms Normal condition *2 Just after See Fig. 1 Condition AOUT, R1 = R3 Low-group tone High-group tone Min. –16.5 –15.5 0 –1.5 — 250 250 –46 — — ±3.8 –6 — 37 DTTIM = "1" DTTIM = "0" DTTIM = "1" DTTIM = "0" DTTIM = "1" DTTIM = "0" DTTIM = "1" DTTIM = "0" DTTIM = "1" DTTIM = "1" DTTIM = "0" DTTIM = "1" DTTIM = "0" DTTIM = "1" DTTIM = "0" DTTIM = "1" DTTIM = "0" 120 70 49 34 — — 30 20 30 20 30 21 — — 6 1 21 15 Typ. –14.5 –13.5 1 — — — — — — — — — –12 — — — — — — — 45 32 48 35 — — — — 8 1.7 29 21 Max. –12.5 –11.5 2 +1.5 –23 — ns See Fig. 2. For each single tone For each single tone With respect to the nominal frequency With respect to the nominal frequency High-group tone/low-group tone Noise (0.3 kHz to 3.4 kHz) level/tone level 380 Hz to 420 Hz — –10 –60 ±1.5 % — +6 — — — — — — 24 9 57 42 77 62 — — 10 3 10 3 35 27 ms dB dBm *1 Unit dBm *1 dB % dB High-group tone/low-group tone With respect to the nominal frequency Harmonics/Fundamental frequency See Fig. 2. mode change *3 DTTIM = "0" 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". (VDD = 2.5 V to 3.6 V, Ta = –40°C to +85°C) Parameter Symbol VAOM VDM fOM fOS fAM fAS Condition Measured at AOUT pin, R1 = R2 Mark signal/space signal Mark, TD = "1" Originate mode Answer mode TD Æ AOUT Measured at AIN. FSK modulation signal Answer mode : 1080 Hz Originate mode : 1750 Hz VR2 open at AIN pin OFF Æ –6 dBm OFF Æ –40 dBm –6 dBm Æ OFF –40 dBm Æ OFF 300 bps,1 : 1 pattern VNRTS/V receive modem signal NRTS : 2765 Hz ±30 Hz AIN Æ RD OFFÆON ONÆOFF Space, TD = "0" Mark, TD = "1" Space, TD = "0" Min. –11 –1.5 976 1176 1646 1846 — –48 *1 — –48 — — 5 20 — — Typ. –9 0 980 1180 1650 1850 3.5 — –44 –46 2 8 14 31 23 — Max. –7 1.5 984 1184 1654 1854 — –6 –42 — — — 22 40 — ±10 % ms dB dBm ms Hz Unit dBm dB AC Characteristics (Modem) Modem Transmit Level Signal Level Relative Value Modem Transmit Carrier Frequency Transmit Signal Output Deray Time Modem Receive Signal Level Carrier Detection (CD) Signal Level CD Level Hysteresis CD Delay Time CD Hold Time Demodulated Data Bias Distortion NRTS Signal Versus Modem Receive Signal Allowable Level Ratio Receive data output Delay Time tADD VAIM VON VOFF VHYS tCDD1 tCDD2 tCDH1 tCDH2 DBS VNR — — –2 dB tRDD — 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) Parameter CPT Detect Level CPT Non-Detect Level CPT Detect Frequency CPT Non-Detect Frequency CPT Detect Delay Time CPT Detect Hold Time Symbol VDETCP VREJCP fDETCP fREJCP tDELCP tHOLCP 400 Hz 400 Hz See Fig. 3. See Fig. 3. — — Condition Min. –40 — 380 500 — — — Typ. — — — — — 20 15 Max. –6 –60 420 — 300 — — Unit dBm dBm Hz Hz ms ms 8/21 ¡ Semiconductor AC Characteristics MSM7715 (VDD = 2.5 V to 3.6 V, Ta = –40°C to +85°C) Parameter Transmit Signal Output Level Output Load Resistance Output Impedance Input Impedance Output DC Potential Symbol VAOUT RLX RLVR1 RLAO ROX RAI VSG VDCAO VREF VS1 VS2 Out-of-band Output Noise VS3 Measured at AOUT R1= 30 kW C4 = 680 pF AOUT MOD, DTO, GAT2 Resistor between VR1 and SGO AOUT AOUT, MOD, DTO, GAT2, VR1, SGO GAT1, AIN SGO AOUT Potential difference between VR1 and SGO 4 kHz to 8 kHz 8 kHz to 12 kHz every 4 kHz bandwidth of 12 kHz or more — –70 –60 Condition Min. — 20 40 30 — — — 0.7 — — Typ. — — — — 100 10 VDD/2 0.75 — — Max. 1.1 — — — — — — 0.8 –45 –65 dBm W MW V kW Unit Vp-p VDD/2–0.1 VDD/2 VDD/2+0.1 9/21 ¡ Semiconductor MSM7715 TIMING DIAGRAM When DTMF is received tC tI tS tP tB AIN signal tG DT1 to 4 tD SP tSP Figure 1 DTMF Receive Timing tS tI tP tB : 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. tSP tC tG1n tD 10/21 ¡ Semiconductor When the DTMF tone is sent MSM7715 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 C2 X2 3.579545 MHz 3.579545 MHz X2 X1 Figure 4 Connection of the Crystal Resonator Signal ground Figure 5 Connection of the External Clock 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. C3 + – + – To the peripherals C6 SGO 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. + – SGC SG voltage generating circuit To the internal circuit 12/21 ¡ Semiconductor Operation mode selection MSM7715 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 Functional Block Operation Mode DTMF signal transmit DTMF signal receive DTMF GEN. * * * * O A O A * * * * * * * * * * DTMF FSK REC. MODEM CPT DET. CPW = "1" * CPW = "0" * MODE 3 0 0 0 0 1 1 1 1 2 0 0 1 1 0 0 1 1 1 0 1 0 1 DTMF mode Normal Originate (O) operation Answer (A) 0 Modem Analog loopback 1 mode Test (ALB) mode 0 Remote digital loopback (RDLB) 1 * 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 Modem signal flow Figure 7 shows the signal flow during normal modem operation. MSM7715 AIN Line AOUT Receive filter Demodulator RD Received data Transmit filter Modulator 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 Received data [ALB] TD Transmit filter AOUT Modulator Transmitted data AIN [RDLB] AOUT Receive filter Demodulator RD Received data Transmit filter Modulator TD Transmitted data Figure 8 Signal Flow in Test Mode 14/21 ¡ Semiconductor DTMF signal code MSM7715 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 Low-group signal (Hz) 697 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 770 852 941 High-group signal (Hz) 1209 * * * 1336 1477 1633 DT4 DT3 DT2 DT1 DTG4 DTG3 DTG2 DTG1 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 Button 1 2 3 4 5 6 7 8 9 0 * # A B C D 15/21 ¡ Semiconductor Microcontroller interface MSM7715 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 DT3 DT4 DTMF Receiver DTG1 DTG2 DTG3 DTG4 DTMF Generator Figure 9 Microcontroller Interface Example 16/21 ¡ Semiconductor Setting the transmit signal level MSM7715 4dB VAO AOUT RC-LPF + – GAT2 C4 R1 GAT1 R3 R2 DTO DTMF Generator MOD 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 External adjustment of the carrier detection level MSM7715 11 VR1 VR2 SG r1 r2 VREF R4 12 R5 6 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 Analog Interface C7 r4 4 dB VT VR R9 R8 – + AMP2 R7 C8 R6 R14 – + C9 AIN R15 SGO R11 R12 R15≥60 kW SG AOUT – + AMP1 – + r3 MSM7715 Line 600 W : 600 W 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. + – R10 600 W R13 19/21 ¡ Semiconductor MSM7715 APPLICATION CIRCUIT Line R10 R9 – + R11 R13 – + R14 R7 C7 Positive Supply C9 R15 C5 –+ SGO AIN VDD AOUT PON R1 C4 SGC GAT1 GAT2 SP C3 C6 C8 R6 – + R8 R2 MOD R3 DTO VR1 VR2 GND DTG1 DTG2 DTG3 DT4 DT3 DT2 DT1 CP CD RD CLK X2 X1 C2 C1 Microcontroller ICTA ICTB DTTIM MODE1 MODE2 MODE3 DTG4 TEN TD RS CPW R12 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 Package weight (g) Epoxy resin 42 alloy Solder plating 5 mm or more 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