Datasheet MSM7715GS-2K Datasheet (OKI)

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¡ Semiconductor MSM7715

¡ Semiconductor

This version: Jan. 1998

Previous version: Nov. 1996

MSM7715

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)

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¡ Semiconductor MSM7715

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BLOCK DIAGRAM

DT1 DT2 DT3 DT4 SP DTTIM

CP CPW

RD TD

CLK X2 X1

MODE1 MODE2 MODE3 ICTA ICTB

TEN

DTG1 DTG2 DTG3 DTG4

AIN

AOUT

GAT2 GAT1

MOD

VR1

VR2

SGO

SGC

DTO

PON

GND

Mode Select

Test

FSK Modem

Carrier

Detector

CPT

Detector

DTMF

Receiver

2765 Hz

BEF

PreLPF

Smooth

Voltage

Ref.

DTMF

Generator

+ –

– +

* * * * *

Power ON

+3 V

0 V

4 dB

Note) DT1 to DT4 :

3-state outputs

* :

Input with

pull-up resistor

¡ Semiconductor MSM7715

PIN CONFIGURATION (TOP VIEW)

DTG343DTG242DTG141GND40VR239VR138DTO37MOD36GAT235GAT134SGC

DTG4

TEN

CPW ICTA ICTB

DTTIM MODE1 MODE2 MODE3

10 11

1 2 3 4 5 6 7 8 9

13X214NC15

16RD17CD18CP19

CLK

DT120DT221DT322DT4

33 32 31 30 29 28 27 26 25 24 23

NC SGO AIN NC V

NC AOUT NC NC

PON

NC : No connect pin

44-Pin Plastic QFP

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¡ Semiconductor MSM7715

PIN DESCRIPTION

Pin No. I/OName

DTG4

TEN 2

TD 3

RS 4

CPW 5

ICTA 6 ICTB 7

DTTIM 8

MODE1 9 MODE2 10 MODE3 11 X1 12 X2 13 CLK 15

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 V

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

RD 16

CD 17

CP 18

DT1 19 DT2 20 DT3 21 DT4 22

SP 23

PON 24

AOUT 27

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.

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.

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.

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¡ Semiconductor MSM7715

Pin No. I/OName

—

AIN 31 I

SGO 32 O

SGC 34

—

GAT1 35 I GAT2 36 O MOD 37 O DTO 38 O

VR1 39 O

VR2 40 I GND 41

— DTG1 42 DTG2 43 DTG3 44

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 V 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.

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¡ Semiconductor MSM7715

ABSOLUTE MAXIMUM RATINGS

Parameter Condition UnitRating

Power Supply Voltage Input Voltage Storage Temperature

Symbol

STG

Ta = 25°C

With respect to GND

—

RECOMMENDED OPERATING CONDITIONS

Parameter Min. Unit

Power Supply Voltage Operating Temperature Range

Input Voltage

Input Clock Frequency X1/X2 Load Capacitance SGC Bypass Capacitance SGO Bypass Capacitance V

Bypass Capacitance

Oscillation Frequency Frequency Deviation

Temperature Characteristics

CLK

C1, C2

C3 C6 C5 — —

—

Crystal

Equivalent Series Resistance

—

ConditionSymbol Typ. Max.

— —

—

Against 3.579545 MHz

— — — 0.1 — — — —

At 25°C ±5°C

At –40°C to +85°C

—

–0.3 to 7

–0.3 to VDD + 0.3

–65 to +150

2.5

3.0

–40

0.8 V

–0.1

— —

10 —

3.579545

–100

–50

—

— — — — 12

—

V V

°C

3.6 +85 V

0.2 V +0.1

—

°C

% pF

—

MHz

—

+100

ppm

+50

W

Load Capacitance

—

ELECTRICAL CHARACTERISTICS

DC Characteristics

= 2.5 V to 3.6 V, Ta = –40°C to +85°C)

Parameter Min. Unit

Power Supply Current

Input Current

Output Voltage

I I

V V V V

DD1

DD2

DDS

OH1

OL1

OH2

OL2

PON = "0"

= V

VIL = 0 V

CLK C

£10 pF

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

ConditionSymbol Typ. Max.

Modem mode DTMF mode Power-downPON = "1"

— —

— –10 –50

IOH = –100 mA I

= 100 mA

= –100 mA

= 100 mA

– 0.1

0.9 V 0

2.4 1

—

–10

— — — —

5 20 10 10

0.1

0.1 V

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¡ Semiconductor MSM7715

AC Characteristics (DTMF)

(

VDD = 2.5 V to 3.6 V, Ta = –40°C to +85°C)

Parameter Min. Unit

Transmit Level

Transmit Signal Level Relative Value

DTTL

DTTH

DTDF

AOUT, R1 = R3

High-group tone/low-group tone

ConditionSymbol Typ. Max.

Low-group tone High-group tone

–16.5 –15.5

–14.5 –13.5

–12.5 –11.5

dBm

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

DDT

THD

SDT

HDT

DETDT

REJDT

DETDT

REJDT

TWIST

N/S

With respect to the nominal frequency

Harmonics/Fundamental frequency

See Fig. 2.

For each single tone For each single tone

With respect to the nominal frequency

High-group tone/low-group tone

Noise (0.3 kHz to 3.4 kHz) level/tone level

–1.5

—

250

–46

—

±3.8

–6

—

— —

—

–12

+1.5

–23

—

–10 –60

±1.5

—

dBm

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

REJ400

t t t t

t t

G11

G12

G21

G22

t t t t

SP1

SP2

t t

380 Hz to 420 Hz

DTTIM = "1" DTTIM = "0" DTTIM = "1"

120

70 49

— — — —

See Fig. 1

DTTIM = "0"

Normal condition *2 Just after mode change *3

DTTIM = "1" DTTIM = "0" DTTIM = "1" DTTIM = "0" DTTIM = "1" DTTIM = "0" DTTIM = "1" DTTIM = "0" DTTIM = "1" DTTIM = "0" DTTIM = "1" DTTIM = "0"

> 80 ms

> 44 ms

DTTIM = "1" DTTIM = "0"

34 — — 30 20 42

30 21 — —

1 21 15 27

— — — 45 32 4830 77 3520 62 — — — —

1.7 29 21

— 24

— — 10

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¡ Semiconductor MSM7715

Note: *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 Min. Unit

Modem Transmit Level Signal Level Relative Value

Modem Transmit Carrier Frequency

AOM

Measured at AOUT pin, R1 = R2 Mark signal/space signal

Originate mode

Answer mode

Transmit Signal Output Deray Time Modem Receive Signal Level

Carrier Detection (CD) Signal Level

CD Level Hysteresis

CD Delay Time

CD Hold Time

ADD

AIM

OFF

HYS

CDD1

CDD2

CDH1

CDH2

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

ConditionSymbol Typ. Max.

–11 dBm

–9 –7

–1.5 0 1.5 Mark, TD = "1" Space, TD = "0" Mark, TD = "1" Space, TD = "0"

976 980 984 1176 1180 1184 1646 1650 1654 1846 1850 1854

— 3.5 —

–48 *1 — –6 OFFÆON ONÆOFF

— –44 –42

–48 –46 —

—2— —8—

51422 20 31 40 —23—

dBm

Demodulated Data Bias Distortion

NRTS Signal Versus Modem Receive Signal Allowable Level Ratio

Receive data output Delay Time

RDD

300 bps,1 : 1 pattern

/V receive modem signal

NRTS

NRTS : 2765 Hz ±30 Hz

AIN Æ RD

— — ±10

——–2

—5—

*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 Min. Unit

CPT Detect Level CPT Non-Detect Level CPT Detect Frequency

CPT Non-Detect Frequency

CPT Detect Delay Time CPT Detect Hold Time

DETCP

REJCP

DETCP

REJCP

DELCP

HOLCP

400 Hz 400 Hz See Fig. 3.

See Fig. 3.

ConditionSymbol Typ. Max.

–40 dBm

— dBm— –60

380 Hz— 420 500

— — 300

— —

—ms20 — —ms15 —

—–6

——

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¡ Semiconductor MSM7715

AC Characteristics

(

VDD = 2.5 V to 3.6 V, Ta = –40°C to +85°C)

Parameter Min. Unit

Transmit Signal Output Level

Output Load Resistance

Output Impedance Input Impedance

Output DC Potential

Out-of-band Output Noise

AOUT

LVR1

LAO

DCAO

REF

V V

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

Measured at AOUT

R1= 30 kW C4 = 680 pF

ConditionSymbol Typ. Max.

— 20 40 30 — —

VDD/2–0.1

— — — —

100

VDD/2

1.1 — — — — —

VDD/2+0.1

—VDD/2 —

0.7 0.75 0.8 4 kHz to 8 kHz 8 kHz to 12 kHz

— — –45

— — –65 every 4 kHz bandwidth of

— –70 –60 12 kHz or more

Vp-p

kW

W

MW

dBm

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¡ Semiconductor MSM7715

TIMING DIAGRAM

When DTMF is received

AIN signal

DT1 to 4

G1n

Figure 1 DTMF Receive Timing

: 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 t

G1n

: 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

DTG1

DTG2

DTG3

DTG4

DTO

SDT

HDT

941 Hz + 1447 Hz

Figure 2 DTMF Transmit Timing

When the call progress tone (CPT) is detected

AIN

CP CPW = "1"

CPW = "0"

DELCP

Figure 3 Call Progress Tone Detect Timing

400 Hz

HOLCP

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¡ 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.

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.

To the

peripherals

SGC

SGO

–

SG voltage

generating

circuit

–

To the internal circuit

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.

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¡ 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

000 010 001 011 100 110 101 111

DTMF mode

Modem

mode

Operation Mode

DTMF signal transmit DTMF signal receive

Normal

operation

Test

mode

Originate (O) Answer (A)

Analog loopback (ALB)

Remote digital loopback (RDLB)

O A O A

DTMF

GEN.

DTMF

REC.

Functional Block

FSK

MODEM

* * * * * *

CPT DET.

CPW = "1"

* * * * * *

CPW = "0"

* 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.

Received data

Transmitted data

Line

AIN

AOUT

Receive filter Demodulator

Transmit filter Modulator

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

Receive filter Demodulator

Received data

[ALB]

[RDLB]

AOUT

AIN

AOUT

Transmit filter Modulator

Receive filter Demodulator

Transmit filter Modulator

Figure 8 Signal Flow in Test Mode

Transmitted data

Received data

Transmitted data

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¡ 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

**10001 **20010 **30011

**A1101

770 852 941 1209 1336 1477 1633

**40100 **50101 **60110

**70111 **81000 **91001

**01010 ***1011 **#1100

**B1110

**C1111

**D0000

High-group signal (Hz)

DT4

DTG4

DT3

DTG3

DT2

DTG2

DT1

DTG1

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¡ 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.

Microcontroller

DT1

DT2

DTMF Receiver

DT3

DT4

DTG1

DTG2

DTMF Generator

DTG3

DTG4

Figure 9 Microcontroller Interface Example

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¡ Semiconductor MSM7715

Setting the transmit signal level

4dB

VAO

AOUT

GAT2

RC-LPF

+ –

GAT1

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.

V V

: Level of the modem signal at the AOUT pin when R1 = R2 (dBm)

AOM

: Level of the DTMF signal at the AOUT pin when R1 = R3 (dBm)

AODT

When external resistors (R1, R2, R3) are changed, the signal level at AOUT is as follows:

VAO (modem) = 20 ¥ log (R1/R2) + V VAO (DTMF) = 20 ¥ log (R1/R3) + V

AOM

AODT

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)

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¡ Semiconductor MSM7715

External adjustment of the carrier detection level

VR1

VR2

VREF

: 300 kW, r2 : 600 kW

COMP

R4 + R5 ≥ 20 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 r Rb = R5 ¥ r2/(R5 + r2), Parallel-connected resistance of R5 and r

VON = 20 ¥ log (Rb/(Ra + Rb)) –40.5 (dBm) V

= 20 ¥ log (Rb/(Ra + Rb)) –42.5 (dBm)

OFF

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

4 dB

AIN

SGO

– +

–

Line

600 W : 600 W

–

AMP2

R11 R12

R10

600 W

AMP1

R13

C8 – +

R14

– +

R15≥60 kW

R15

AOUT

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.

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¡ Semiconductor MSM7715

APPLICATION CIRCUIT

Line

R10

–

R2 R3

R14

SGC GAT1

GAT2

MOD DTO

VR1 VR2 GND

DTG1 DTG2 DTG3

R13

R15

–

AIN

SGO

DTG4

TENTDRS

–

Positive Supply

PON

AOUT

CPW

ICTA

ICTB

DTTIM

MODE1

DT4 DT3 DT2 DT1

CLK

X2 X1

MODE2

MODE3

R11

R12

Microcontroller

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¡ 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).

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Datasheet MSM7715GS-2K Datasheet (OKI)

Specifications and Main Features

Frequently Asked Questions

User Manual