CMX683E4 - CML Microcircuits

CML Microcircuits

COMMUNICATION SEMICONDUCTOR

CMX683

Call Progress and

"Voice" Detector

D/683/2 May 2006 Provisional Issue

Features Applications

• Detects Single and Dual Call Progress Tones • Worldwide Payphone Systems

• Worldwide Call Progress Tone Compatibility • Telephone Redialling Systems

• "Voice" Detect Outputs (Fast and Slow) • Dialling Modems

• Wide Dynamic Range with Low Falsing • Banking and Billing Systems

• Low Power Operation: 600µA at 3.0V typ. • Telecom Test Equipment

• 3.58MHz Xtal/Clock Oscillator • Telecom Security Systems

1. Brief Description

The CMX683 is a general purpose Call Progress tone detector for use in monitoring the progress of calls

in Public Switched Telephone System (PSTN) applications. Dial Tone, Ringing, Busy and Not Available

states can be distinguished by using the host µC to qualify the cadence of the CP DETECT output. The

CMX683 uses advanced digital techniques to characterise valid Call Progress tones, unwanted tones, line

noise and voice or music signals. In contrast to Call Progress detection devices based on simple filtering

techniques, the CMX683 offers excellent sensitivity coupled with low false detection rates.

The response time of the CMX683 allows it to operate with almost any Call Progress system. In particular

the ‘stuttered dial tone’ of voice mail messaging systems is supported. The use of statistical processing

techniques, which analyse signal frequency, duration and amplitude, enable the CMX683 to distinguish

voice or music activity from DTMF or Call Progress signals. Separate outputs integrate the "voice" activity

over both shorter and longer periods, enabling payphone and other billing systems to commence charging

when a line connection has been established. A single 3.58MHz crystal ensures accurate and repeatable

performance. With supply requirements between 2.7V and 5.5V and a low current consumption, the

CMX683 can be easily integrated into a wide range of telecom equipments. The CMX683 has a similar

pinout to all commonly used Call Progress detectors and is available in DIP, TSSOP or SOIC packages.

Call Progress and "Voice" Detector CMX683

CONTENTS

Section Page

1. Brief Description.....................................................................................1

2. Block Diagram.........................................................................................3

3. Signal List................................................................................................4

4. External Components.............................................................................5

5. General Description................................................................................6

5.1 Overall Function Description....................................................6

5.2 Glossary......................................................................................6

5.3 Block Diagram Description.......................................................7

5.4 Decode Output Truth Table ......................................................7

6. Application Notes ...................................................................................9

7. Performance Specification...................................................................11

7.1 Electrical Performance............................................................11

7.2 Packaging.................................................................................14

Call Progress and "Voice" Detector CMX683

2. Block Diagram

Figure 1 Block Diagram

Call Progress and "Voice" Detector CMX683

3. Signal List

SOIC

Package TSSOP

Package DIP

Package

D4 E4 P1 Signal Type Description

Pin No. Pin No. Pin No. Name

1 1  NC Reserved for future use. Do not make any

connection to this pin.

2 2 1 XTAL I/P The input to the on-chip oscillator, to be used

in conjunction with the XTALN output. An

external crystal only is required. All other

components are on-chip. If the on-chip

oscillator is not used, this pin should be

connected to VSS.

3 3  CLOCK IN I/P The external clock input. Connect the

CONFIG pin to VDD to enable this input.

4 4 2 XTALN O/P The inverted output of the on-chip oscillator.

Leave unconnected if not used.

5 5 3 ENABLE I/P A logic 1 applied to this input enables all

detector outputs. A logic 0 will force all

detector outputs to a logic 0.

6 6  VOICE

SLOW

O/P When a Non Call Progress signal is detected

this output goes to a logic 1. (See Table 1).

7 7 4 CP

DETECT

O/P When a Call Progress signal is detected this

output goes to a logic 1. (See Table 1).

8 8  NC Reserved for future use. Do not make any

connection to this pin.

9 9  NC Reserved for future use. Do not make any

connection to this pin.

10 10 5 SIGIN I/P Signal input (which should be ac coupled as

the dc bias on this pin is set internally).

11 11  NC Reserved for future use. Do not make any

connection to this pin.

12 12 6 VSS Power The negative supply rail (ground).

13 13 7 VOICE

FAST

O/P When a Non Call Progress signal is detected

this output goes to a logic 1. (See Table 1).

14 14  VREF O/P Internally generated reference voltage held at

½VDD and available to power external circuits.

15 15 8 VDD Power The positive supply rail. This pin should be

decoupled to VSS by a capacitor.

16 16  CONFIG I/P Oscillator configuration. Leave unconnected

when using an external crystal. This pin has

an internal pulldown to the VSS pin.

Notes: I/P = Input O/P = Output NC = No Connection

Call Progress and "Voice" Detector CMX683

4. External Components

Typical Values:

C1 0.1µF ± 20%

C2 0.1µF ± 20%

X1 3.579545MHz (refer to Section 7.1)

Note: C1 is not required if the input is referenced to VREF.

Figure 2 Recommended External Components

To achieve good noise performance, VDD decoupling and protection of the receive path from extraneous

in-band signals are very important. It is recommended that the printed circuit board is laid out with a

ground plane in the CMX683 area to provide a low impedance connection between the VSS pin and the

VDD decoupling capacitor.

Call Progress and "Voice" Detector CMX683

5. General Description

5.1 Overall Function Description

The CMX683 Call Progress Tone Detector uses different tone detection methods from those

commonly found with other products.

Many traditional devices from other suppliers use a bandpass filter followed by an energy

detector. The filter is usually designed to pass input signals with a frequency between about 300

and 700 Hz, and the amplitudes of signals in this range are then checked against a level

threshold. Any signal of acceptable level in this frequency band is classed as a Call Progress

tone, including signals due to speech, music, DTMF and noise. False outputs are a common

feature with these products. To avoid background noise causing a stuck “detect” output, the

sensitivity of such devices is often poor.

The CMX683, by contrast, uses a stochastic signal processing technique based on analysis in

both the frequency and time domains, with signal amplitude forming part of the decision process.

This analysis includes checks on whether the signal has a profile which matches international

standards for Call Progress tones, or whether the profile is more likely to match that of DTMF,

speech, music, noise or no signal. The frequency response of the CMX683 is confined to the Call

Progress band, plus a small extension above and below this band. This ensures that the

CMX683 will not respond to FAX, Modem or other out-of-band signals.

The following Glossary and the Decode Truth Table in section 5.4 provide a simple explanation of

the decoding functions and features offered by the CMX683.

5.2 Glossary

Call Progress Tones: The single and dual frequency tones in the range 350 to 620 Hz which

are specified widely for call progress signalling.

Call Progress Band: The nominal range 315 to 650 Hz within which the CMX683 will detect Call

Progress tones. The detection algorithm requires that these tones have the characteristics typical

of Call Progress Tones.

No Signal: The absence of an input signal (below the detection threshold) or

A signal below 190Hz or

A signal between 900Hz and 10kHz.

Non Call Progress ("Voice") Signal:

A signal falling within the nominal range of 190 to 895 Hz,

but NOT within the Call Progress band or

A signal falling within the nominal range of 190 to 895 Hz,

but NOT meeting the Call Progress detection requirements for that part

of the signal which falls within the Call Progress band. Subject to the

duration and other characteristics of such signals, the CMX683 will

usually interpret these as a Non Call Progress signal (ie "Voice" activity).

Note that signals above 10kHz should not exceed -38dB (relative to 775mVrms), to avoid

aliasing.

Nominal: Subject to dynamic tolerances within the signal analysis process. Absolute values are

not material or adverse to performance.

Call Progress and "Voice" Detector CMX683

5.3 Block Diagram Description

Amplifier

The input signal is amplified by a self-biased inverting amplifier. The dc bias of this input is

internally set at ½VDD.

Signal Analyser

The frequency range, quality and consistency of the input signal is analysed by this functional

block. To be classified as a Call Progress signal the input signal frequencies must lie between

315 and 650 Hz, and the signal to noise ratio must be 16dB or greater. The signal must have a

minimum rms amplitude of about -60dB (relative to 775mVrms) and the signal must be consistent

over a period of about 80ms. These decode criteria are continuously monitored and the

assessment is updated every 6ms. To be classified as a Non Call Progress ("Voice") signal the

input signal frequencies must lie between 190 and 895 Hz and the frequencies must not match

the predefined profiles for DTMF or Call Progress signals. The signal must have a minimum rms

amplitude of about -60dB (relative to 775mVrms) and the signal must show activity over a period

of about 145ms (fast response) or 500ms (slow response).

Control and Output Logic

This block categorises the nature of the signal into Call Progress and Non Call Progress output

states. A Non Call Progress output is further checked for activity over a longer detection period,

resulting in a VOICE FAST output responding to speech/music in around 90ms and a VOICE

SLOW output (with a more consistent detection) responding in around 370ms. If the VOICE

FAST output is at logic 1 for more than 51% of the previous 728ms then the VOICE SLOW output

will change to a logic 1. If the VOICE FAST output is at logic 1 for less than 10% of the previous

728ms then the VOICE SLOW output will change to a logic 0. The Decode Output Truth Table on

the following page gives further details. Also refer to the timing diagram in Figure 5.

Level Detector

The Level Detector operates by measuring the level of the amplified input signal and comparing it

with a preset threshold, which has a nominal value of -42dB (relative to 775mVrms). The Level

Detector output goes to the Control and Output Logic block, where the Call Progress signal and

Voice detector outputs are gated with the Level Detector output. The CP DETECT, VOICE FAST

and VOICE SLOW outputs are valid only if the input signal level is above this preset threshold.

Xtal Oscillator

If the on-chip Xtal oscillator is to be used, an external 3.58MHz crystal (X1) only is required and

the CONFIG pin should be left unconnected. If an external clock source is to be used, the clock

should be connected to the CLOCK IN input pin and the XTAL pin should be connected to VSS.

The XTALN pin should be left unconnected and the CONFIG pin must be connected to VDD.

Note that this external clock option is not available with the P1 package.

Enable Input

A logic 1 applied to this input enables the whole device, including the outputs and the xtal

oscillator circuit. About 15ms should be allowed for the oscillator to start up, once enabled.

A logic 0 applied to this input resets the device, then powersaves the xtal oscillator, the signal

analyser, level detector and control and output logic. In addition the CPDETECT, VOICE FAST

and VOICE SLOW outputs will be cleared to a logic 0. The VREF supply is maintained at ½VDD, so

will continue to draw a small amount of current.

5.4 Decode Output Truth Table

In the following Truth Table it should be noted that it is possible to get both CP DETECT and

VOICE FAST or VOICE SLOW outputs simultaneously at logic 1. If the activity is initially

Call Progress and "Voice" Detector CMX683

consistent with and meets the Call Progress signal profile, the CP DETECT output will go to logic

1. If the activity subsequently meets the Non Call Progress signal profile, the VOICE FAST output

(and, eventually, the VOICE SLOW output) will go to a logic 1 without changing the CP DETECT

output. The host µC must then use cadence information to decide what signal is present. See

section 6.

Note that CP DETECT responds to the whole range of Call Progress tones from 315 to 650 Hz.

CONDITIONS CP DETECT

"VOICE"

FAST/SLOW

No Signal 0 0

Call Progress Signal:

Will detect 350+440, 400+450, 440+480, 400,

425, 440, 450, 480+620, 600 and 620Hz tones

1 0

DTMF Signal 0 0

Non Call Progress Signal (eg voice) 0 1

FAX/Modem or other out-of-band signals 0 0

Table 1 Decode Output Truth Table

Call Progress and "Voice" Detector CMX683

6. Application Notes

On power-up, it will take no more than 15ms to initialise the internal state. This delay should be

accounted for before the CP DETECT, VOICE SLOW and VOICE FAST outputs are valid.

Figure 3 A typical Telephone Line Circuit Application

R1 470kΩ R4 470kΩ C2 0.1µF

R2 470kΩ R5 100kΩ C3 0.01µF 250V

R3 470kΩ R6 100kΩ C4 0.01µF 250V

C5 0.1µF

Note: 1. Resistors ±1%, Capacitors ±20%, unless otherwise stated.

2. A low offset opamp is needed. The decoupling capacitor C1 (see Figure 2) is not required if

the quiescent dc level at the opamp output is the same as VREF.

All outputs should be examined for cadence information. Sometimes a call progress signal will

not cause the CPDETECT output to go to a 1 because the signal has a high harmonic content, or

is amplitude or frequency modulated by another tone. Often this will result in a “voice” detection

instead, so it is good practice to examine the VOICE FAST output for a regular call progress

cadence. A typical detection strategy might be:

To detect Call Progress tones

Examine CPDETECT cadence first, then examine VOICE FAST cadence. Ignore any output

which has an unexpected cadence. A more accurate result will be obtained by checking the

cadence over a long period of time.

To detect “Voice” activity

Examine the VOICE FAST cadence first. If this is irregular, it probably signifies “voice” activity.

This can be confirmed by examining the VOICE SLOW output, which integrates the “voice”

detection over a much longer period. If this output goes to a 1 and stays at a 1 for a long period

of time, it has almost certainly detected “voice” activity.

Call Progress and "Voice" Detector CMX683

The detection process for both “voice” and call progress tones depends on stochastic signal

processing techniques and requires the customer to examine the cadence (timing) information

before a final decision can be made. Frequently the call progress tone will contain noise, which

may cause the CMX683 to respond with a VOICE FAST output instead. An example of this is

shown in Figure 4, where the VOICE FAST output is maintained until the call progress tone has

ceased, as illustrated by time L2.

Figure 4: CMX 683 Voice / Tone Response

Call Progress and "Voice" Detector CMX683

7. Performance Specification

7.1 Electrical Performance

7.1.1 Absolute Maximum Ratings

Exceeding these maximum ratings can result in damage to the device.

Min. Max. Units

Supply (VDD - VSS) -0.3 7.0 V

Voltage on any pin to VSS -0.3 VDD + 0.3 V

Current into or out of VDD and VSS pins -30 +30 mA

Current into or out of any other pin -20 +20 mA

P1 Package Min. Max. Units

Total Allowable Power Dissipation at Tamb = 25°C 800 mW

... Derating 13.0 mW/°C

Storage Temperature -55 +125 °C

Operating Temperature -40 +85 °C

E4 Package Min. Max. Units

Total Allowable Power Dissipation at Tamb = 25°C 300 mW

... Derating 5.0 mW/°C

Storage Temperature -55 +125 °C

Operating Temperature -40 +85 °C

D4 Package Min. Max. Units

Total Allowable Power Dissipation at Tamb = 25°C 800 mW

... Derating 13.0 mW/°C

Storage Temperature -55 +125 °C

Operating Temperature -40 +85 °C

Operating Limits

Correct operation of the device outside these limits is not implied.

Notes Min. Max. Units

Supply (VDD - VSS) 2.7 5.5 V

Xtal Frequency 3.57 3.59 MHz

Call Progress and "Voice" Detector CMX683

7.1.3 Operating Characteristics

Xtal Frequency = 3.579545MHz, S/N = 16dB, Noise Bandwidth = 5kHz,

DD = 3.0V to 5.0V, Tamb = -40°C to +85°C. 0dB = 775mVrms.

Notes Min. Typ. Max. Units

DC Parameters

IDD (ENABLE = 0) (VDD = 5.0V) 1 – 250 – µA

IDD (ENABLE = 1) (VDD = 5.0V) 1 – 1.0 1.5 mA

IDD (ENABLE = 1) (VDD = 3.0V) 1 – 0.6 1.0 mA

VREF Output 8 45% 50% 55% VDD

AC Parameters

SIGIN pin

Input Impedance 2 – 0.1 – MΩ

Minimum Input Signal Level – -38.0 – dB

Input Signal Dynamic Range 40.0 – – dB

Signal to Noise Ratio 16.0 – –

Clock Input

‘High’ Pulse Width 3 100 – – ns

‘Low’ Pulse Width 3 100 – – ns

Gain (I/P = 1mVrms at 100Hz) 20.0 – – dB

Level Detector

Must Detect Signal Level 4 -38.0 – – dB

Must Not Detect Signal Level 4 – – -50.0 dB

Call Progress Band 7

Must Detect Range 315 – 650 Hz

Must Not Detect Range 750 – 250 Hz

Logic Interface

Input Logic 1 Level 5 80% – – VDD

Input logic 0 level 5 – – 20% VDD

Input leakage current (Vin = 0 to VDD) 5 -5.0 – +5.0 µA

Input Capacitance 5 – 7.5 – pF

Output logic 1 level (lOH = 120µA) 6 90% – – VDD

Output logic 0 level (lOL = 360µA) 6 – – 10% VDD

Notes: 1. Not including any current drawn from the CMX683 pins by external circuitry.

2. Small signal impedance over the frequency range 100Hz to 2000Hz and at VDD = 5.0V.

3. Timing for an external input to the CLOCK IN pin.

4. Input signal level at VDD = 5.0V, scale signal for different VDD.

5. ENABLE and CONFIG pins.

6. CP DETECT, VOICE FAST and VOICE SLOW pins.

7. Nominal values which are subject to dynamic tolerances within the signal analysis process,

as a result of using stochastic signal processing techniques.

8. Load impedance on this output must exceed 330kΩ.

Call Progress and "Voice" Detector CMX683

Electrical Performance (continued)

Figure 5 µC Parallel Interface Timings

For the following conditions unless otherwise specified:

Xtal Frequency = 3.579545MHz, VDD = 3.0V to 5.0V, Tamb = -40°C to +85°C, S/N = 20dB.

Notes Min. Typ. Max. Units

Signal Timings (ref. Figure 5)

tl Burst Length Ignored - - 40.0 ms

tL Burst Length Detected 80.0 - - ms

tGI Call Progress Tone Gap Length

Ignored

9 - - 20.0 ms

tGD Call Progress Tone Gap Length

Detected

9 40.0 - - ms

tRP Call Progress Tone Response Time 10 - 46 80.0 ms

tDRP Call Progress Tone De-Response

Time

10 - 46 80.0 ms

Notes: 9. Only applies to bursts of the same frequency.

10. Measured with 350 + 440 Hz tone pair.

Call Progress and "Voice" Detector CMX683

7.2 Packaging

Figure 6 SOIC Mechanical Outline: Order as part no. CMX683D4

Figure 7 TSSOP Mechanical Outline: Order as part no. CMX683E4

Call Progress and "Voice" Detector CMX683

2006 CML Microsystems Plc 15 D/683/2

Figure 8 DIP Mechanical Outline: Order as part no. CMX683P1

Call Progress and "Voice" Detector CMX683

Handling precautions: This product includes input protection, however, precautions should be taken to prevent device

damage from electro-static discharge. CML does not assume any responsibility for the use of any circuitry described. No

IPR or circuit patent licences are implied. CML reserves the right at any time without notice to change the said circuitry and

this product specification. CML has a policy of testing every product shipped using calibrated test equipment to ensure

compliance with this product specification. Specific testing of all circuit parameters is not necessarily performed.

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For FAQs see: www.cmlmicro.com/products/faqs/

For a full data sheet listing see: www.cmlmicro.com/products/datasheets/download.htm

For detailed application notes: www.cmlmicro.com/products/applications/

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