Datasheet M-8888-01T, M-8888-01P, M-8888-01SM Datasheet (CLARE)

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DS-M8888-R1

M-8888

DTMF Transceiver

1

Features

·

Advanced CMOS technology for low power con­sumption and increased noise immunity

·

Complete DTMF transmitter/receiver in a single
chip

·

Standard 8051, 8086/8 microprocessor port

·

Central office quality and performance

·

Adjustable guard time

·

Automatic tone burst mode

·

Call progress mode

·

Single +5 Volt power supply

·

20-pin DIP and SOIC packages

·

2 MHz microprocessor port operation

·

Inexpensive 3.58 MHz crystal

Applications

·

Paging systems

·

Repeater systems/mobile radio

·

Interconnect dialers

·

PBX systems

·

Computer systems

·

Fax machines

·

Pay telephone

·

Credit card verification

Description

The M-8888 is a complete DTMF Transmitter
Receiver that features adjustable guard time, auto­matic tone burst mode, call progress mode, and a fully
compatible 8051, 8086/8 microprocessor interface.
The receiver portion is based on the industry standard
M-8870 DTMF Receiver, while the transmitter uses a
switched-capacitor digital-to-analog converter for low­distortion, highly accurate DTMF signaling. Tone
bursts can be transmitted with precise timing by mak­ing use of the automatic tone burst mode. To analyze
call progress tones, a call progress filter can be select­ed by an external microprocessor.

Ordering Information

Pin Connections

Block Diagram

Part # Description

M-8888-01P 20-pin plastic DIP
M-8888-01SM 20-pin plastic SOIC
M-8888-01T 20-pin plastic SOIC,Tape and Reel

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M-8888

Rev. 1

ing the amplifier inputs at VDD/2. Provisions are made
for the connection of a feedback resistor to the op-amp
output (GS) for gain adjustment. In a single-ended
configuration, the input pins should be connected as
shown in the Single-Ended Input Configuration above.
Differential Input Configuration above shows the nec­essary connections for a differential input configura­tion.

Receiver Section

The low and high group tones are separated by apply­ing the DTMF signal to the inputs of two sixth-order

Single-Ended Input Configuration Differential Input Configuration

Functional Description

M-8888 functions consist of a high-performance
DTMF receiver with an internal gain setting amplifier
and a DTMF generator that contains a tone burst
counter for generating precise tone bursts and paus­es. The call progress mode, when selected, allows the
detection of call progress tones. A standard 8051,
8086/8 series microprocessor interface allows access
to an internal status register, two control registers, and
two data registers.

Input Configuration

The input arrangement consists of a differential input
operational amplifier and bias sources (V

REF

) for bias-

Pin Functions

Name Description

IN+ Noninverting op-amp input.

IN- Inverting op-amp input.
GS Gain select. Gives access to output of front end differential amplifier for connection of feedback resistor.

V

REF

Reference voltage output. Nominally VDD/2 is used to bias inputs at mid-rail.

V

SS

Negative power supply input.
OSC1 DTMF clock/oscillator input.
OSC2 Clock output. A 3.5795 MHz crystal connected between OSC1 and OSC2 completes the internal oscillator circuit.
TONE Dual tone multifrequency (DTMF) output.

WR Write input. A low on this pin when CS is low enables data transfer from the microprocessor. TTL compatible.

CS Chip select. TTL input (CS = 0 to select the chip).

RS0 Register select input. See Internal Register Functions on page 7. TTL compatible.

RD Read input. A low on this pin when CS is low enables data transfer to the microprocessor. TTL compatible..

IRQ /CP Interrupt request to microprocessor (open-drain output). Also, when call progress (CP) mode has been selected and

interrupt enabled, the IRQ/CP pin will output a rectangular wave signal representative of the input signal applied at the

input op-amp. The input signal must be within the bandwidth limits of the call progress filter. See Timing Diagrams on

page 11.

D0-D3 Microprocessor data bus. TTL compatible.

ESt Early steering output. Presents a logic high once the digital algorithm has detected a valid tone pair (signal condition).

Any momentary loss of signal condition will cause ESt to return to a logic low.

St/GT Steering input/guard time output (bidirectional). A voltage greater than V

TSt

detected at St causes the device to register

the detected tone pair and update the output latch. A voltage less than V

TSt

frees the device to accept a new tone pair. The

GT output acts to reset the external steering time-constant; its state is a function of ESt and the voltage on St.

V

DD

Positive power supply input.

M-8888

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switched capacitor bandpass filters with bandwidths
that correspond to the low and high group frequencies
listed in the Tone Encoding/Decoding below. The low
group filter incorporates notches at 350 and 440 Hz,
providing excellent dial tone rejection. Each filter out­put is followed by a single-order switched capacitor fil­ter that smoothes the signals prior to limiting. Limiting
is performed by high-gain comparators with hysteresis
to prevent detection of unwanted low-level signals.
The comparator outputs provide full-rail logic swings
at the incoming DTMF signal frequencies.

A decoder employs digital counting techniques to
determine the frequencies of the incoming tones, and
to verify that they correspond to standard DTMF fre­quencies. A complex averaging algorithm protects
against tone simulation by extraneous signals (such
as voice), while tolerating small deviations in frequen­cy. The algorithm provides an optimum combination of
immunity to talkoff with tolerance to interfering fre­quencies (third tones) and noise. When the detector
recognizes the presence of two valid tones (referred to
as signal condition), the early steering (ESt) output
goes to an active state. Any subsequent loss of signal
condition will cause ESt to assume an inactive state.

Steering Circuit:

Before a decoded tone pair is registered, the receiver
checks for a valid signal duration (referred to as “char­acter recognition condition”). This check is performed

by an external RC time constant driven by ESt. A logic
high on ESt causes V

C

(see the Basic Steering Circuit
above) to rise as the capacitor discharges. Provided
that the signal condition is maintained (ESt remains
high) for the validation period (t

GTP

), VCreaches the

threshold (V

TSt

) of the steering logic to register the
tone pair, latching its corresponding 4-bit code (see
the Tone Encoding/Decoding on left) into the receive
data register.

At this point the StGT output is activated and drives V

C

to VDD. StGT continues to drive high as long as ESt
remains high. Finally, after a short delay to allow the
output latch to settle, the delayed steering output flag
goes high, signaling that a received tone pair has
been registered. It is possible to monitor the status of
the delayed steering flag by checking the appropriate
bit in the status register. If interrupt mode has been
selected, the IRQ/CP pin will pull low when the
delayed steering flag is active.

The contents of the output latch are updated on an
active delayed steering transition. This data is pre­sented to the 4-bit bidirectional data bus when the
receive data register is read. The steering circuit works
in reverse to validate the interdigit pause between sig­nals. Thus, as well as rejecting signals too short to be
considered valid, the receiver will tolerate signal inter­ruptions (dropout) too short to be considered a valid
pause. This capability, together with the ability to
select the steering time constants externally, allows
the designer to tailor performance to meet a wide vari­ety of system requirements.

Guard Time Adjustment: The simple steering circuit
shown in the Basic Steering Circuit above is adequate
for most applications. Component values are chosen
according to the formula:

t

REC

= tDP+ t

GTP

TID= tDA+ t

GTA

Tone Encoding/Decoding

F

LOW

F

HIGH

Digit D3 D2 D1 D0

697 1209 1 0 0 0 1
697 1336 2 0 0 1 0
697 1477 3 0 0 1 1
770 1209 4 0 1 0 0
770 1336 5 0 1 0 1
770 1477 6 0 1 1 0
852 1209 7 0 1 1 1
852 1336 8 1 0 0 0
852 1477 9 1 0 0 1
941 1336 0 1 0 1 0
941 1209 * 1 0 1 1
941 1477 # 1 1 0 0
697 1633 A 1 1 0 1
770 1633 B 1 1 1 0
852 1633 C 1 1 1 1
941 1633 D 0 0 0 0

0 = logic low, 1 = logic high

Basic Steering Circuit

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M-8888

Rev. 1

The value of tDPis a device parameter and t

REC

is the
minimum signal duration to be recognized by the
receiver. A value for C1 of 0.1 µF is recommended for
most applications, leaving R1 to be selected by the
designer. Different steering arrangements may be
used to select independently the guard times for tone
present (t

GTP

) and tone absent (t

GTA

). This may be nec­essary to meet system specifications that place both
accept and reject limits on both tone duration and inter­digit pause. Guard time adjustment also allows the
designer to tailor system parameters such as talkoff
and noise immunity. Increasing t

REC

improves talkoff
performance since it reduces the probability that tones
simulated by speech will maintain signal condition long
enough to be registered. Alternatively, a relatively short
t

REC

with a long tDOwould be appropriate for extreme­ly noisy environments where fast acquisition time and
immunity to tone dropouts are required. Design infor­mation for guard time adjustment is shown in the
Guard Time Adjustment above.

Call Progress Filter

A call progress (CP) mode can be selected, allowing
the detection of various tones that identify the progress
of a telephone call on the network. The call progress
tone input and DTMF input are common; however, call
progress tones can only be detected when the CP
mode has been selected. DTMF signals cannot be
detected if the CP mode has been selected (see the
Actual Frequencies vs Standard Requirements on
page 5). The Call Progress Response above indicates
the useful detect bandwidth of the call progress filter.
Frequencies presented to the input (IN+ and IN-) that
are within the accept bandwidth limits of the filter are
hard-limited by a high-gain comparator with the
IRQ/CP pin serving as the output. The square wave
output obtained from the schmitt trigger can be ana-

yzed by a microprocessor or counter arrangement to
determine the nature of the call progress tone being
detected. Frequencies in the reject area will not be
detected, and consequently there will be no activity on
IRQ/CP as a result of these frequencies.

DTMF Generator

The DTMF transmitter used in the M-8888 is capable
of generating all 16 standard DTMF tone pairs with low
distortion and high accuracy. All frequencies are
derived from an external 3.58 MHz crystal. The sinu­soidal waveforms for the individual tones are digitally
synthesized using row and column programmable
dividers and switched capacitor digital-to-analog con­verters. The row and column tones are mixed and fil­tered, providing a DTMF signal with low total harmonic
distortion and high accuracy. To specify a DTMF sig­nal, data conforming to the encoding format shown in
the Tone Encoding/Decoding Table on page 3 must be
written to the transmit data register. Note that this is the
same as the receiver output code. The individual tones
that are generated (f

LOW

and f

HIGH

) are referred to as
low-group and high-group tones. Typically, the high­group to low-group amplitude ratio (twist) is 2 dB to
compensate for high-group attenuation on long loops.

Operation:

During write operations to the transmit data register, 4­bit data on the bus is latched and converted to a 2 of 8
code for use by the programmable divider circuitry to
specify a time segment length that will ultimately deter­mine the tone frequency. The number of time seg­ments is fixed at 32, but the frequency is varied by
varying the segment length. When the divider reaches
the appropriate count as determined by the input code,
a reset pulse is issued and the counter starts again.

Guard Time Adjustment

Call Progress Response

Control Register A Description

Bit Name Function Description

b0 TOUT Tone output A logic 1 enables the tone output. This function can be implemented in either the burst

mode or nonburst mode.

b1 CP/DTMF Mode control In DTMF mode (logic 0), the device is capable of generating and receiving DTMF signals.

When the call progress (CP) mode is selected (logic 1), a 6th-order bandpass filter is enabled to allow
call progress tones to be detected. Call progress tones within the specified bandwidth will be presented
at the IRQ/CP pin in rectangular wave format if the IRQ bit has been enabled (b2 = 1). Also, when the
CP mode and burst mode have both been selected, the transmitter will issue DTMF signals with a burst
and pause of 102 ms (typ) duration. This signal duration is twice that obtained from the DTMF transmit­ter, if DTMF mode had been selected. Note that DTMF signals cannot be decoded when the CP mode
has been selected.

b2 IRQ Interrupt enable A logic 1 enables the interrupt mode. When this mode is active and the DTMF mode has

been selected (b1 = 0), the IRQ/CP pin will pull to a logic 0 condition when either (1) a valid DTMF sig­nal has been received and has been present for the guard time or (2) the transmitter is ready for more
data (burst mode only).

b3 RSEL Register select A logic 1 selects control register B on the next write cycle to the control register address. Subsequent

write cycles to the control register are directed back to control register A.

Active Cell Output Frequency(Hz) % Error

Specified Actual

L1 697 699.1 + 0.30
L2 770 766.2 - 0.49
L3 852 847.4 - 0.54
L4 941 948.0 + 0.74
H1 1209 1215.9 + 0.57
H2 1336 1331.7 - 0.32
H3 1447 1471.9 - 0.35
H4 1633 1645.0 + 0.73

M-8888

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Rev. 1

The divider output clocks another counter that
addresses the sinewave lookup ROM. The lookup
table contains codes used by the switched capacitor
D/A converter to obtain discrete and highly accurate
DC voltage levels. Two identical circuits are used to
produce row and column tones, which are then mixed
using a low-noise summing amplifier. The oscillator
described needs no startup time as in other DTMF
generators, since the crystal oscillator is running con­tinuously, thus providing a high degree of tone burst
accuracy. When there is no tone output signal, the
TONE pin assumes a DC level of 2.5 volts (typically).
A bandwidth limiting filter is incorporated to attenuate
distortion products above 4 KHz.

Burst Mode:

Certain telephony applications require that generated
DTMF signals be of a specific duration, determined

either by the application or by any of the existing
exchange transmitter specifications. Standard DTMF
signal timing can be accomplished by making use of
the burst mode. The transmitter is capable of issuing
symmetric bursts/pauses of predetermined duration.
This burst/pause duration is 51 ms ± 1 ms, a standard
interval for autodialer and central office applications.
After the burst/pause has been issued, the appropriate
bit is set in the status register, indicating that the trans­mitter is ready for more data.

The timing described in the previous paragraph is
available when the DTMF mode has been selected.
However, when call progress (CP) mode is selected, a
secondary burst/pause time is available that extends
this interval to 102 ms ± 2 ms. The extended interval is
useful when precise tone bursts of longer than 51 ms
duration and 51 ms pause are desired. Note that when
CP mode and burst mode have been selected, DTMF
tones may be transmitted only and not received. In
applications where a nonstandard burst/pause time is
desirable, a software timing loop or external timer can
be used to provide the timing pulses when the burst
mode is disabled by enabling and disabling the trans­mitter.

The M-8888 is initialized on powerup sequence with
DTMF mode and burst mode selected.

Single-Tone Generation:

A single-tone mode is available whereby individual
tones from the low group or high group can be gener­ated. This mode can be used for DTMF test equipment
applications, acknowledgment tone generation, and
distortion measurements. Refer to the Control Register
B Description below for details.

Actual Frequencies vs Standard Requirements

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M-8888

Rev. 1

Distortion Calculations:

The M-8888 is capable of producing precise tone
bursts with minimal error in frequency (see the Actual
Frequecies vs Standard Requirements on page 5).
The internal summing amplifier is followed by a first­order low-pass switched capacitor filter to minimize
harmonic components and intermodulation products.
The total harmonic distortion for a single tone can be
calculated using Equation 1, (see Equations on page

7), which is the ratio of the total power of all the extra­neous frequencies to the power of the fundamental fre­quency expressed as a percentage. The Fourier
components of the tone output correspond to V2f... Vnf
as measured on the output waveform. The total har­monic distortion for a dual tone can be calculated
using Equation 2, (see Equations on page 7).

V

L

and VHcorrespond to the low-group and high-group

amplitude, respectively, and V

2

IMD

is the sum of all the
intermodulation components. The internal switched
capacitor filter following the D/A converter keeps dis­tortion products down to a very low level.

DTMF Clock Circuit

The internal clock circuit is completed with the addition
of a standard 3.579545 MHz television color burst
crystal. A number of M-8888 devices can be connect­ed as shown in the Common Crystal Connection on
page 7 using only one crystal.

Microprocessor Interface

The M-8888 uses a microprocessor interface that
allows precise control of transmitter and receiver func­tions. Five internal registers are associated with the
microprocessor interface, which can be subdivided
into three categories: data transfer, transceiver control,
and transceiver status. Two registers are associated
with data transfer operations. The receive data regis­ter, a read-only register, contains the output code of
the last valid DTMF tone pair to be decoded. The data
entered in the transmit data register determines which
tone pair is to be generated (see the Tone
Encoding/Decoding Table on page 3). Data can only
be written to the transmit data register. Transceiver
control is accomplished with two control registers (and
CRB) that occupy the same address space. A write
operation to CRB can be executed by setting the
appropriate bit in CRA. The following write operation to
the same address will then be directed to CRB, and
subsequent write cycles will then be redirected to
CRA. Internal reset circuitry clears the control registers
on powerup; however, as a precautionary measure,
the initialization software should include a routine to
clear the registers. Refer to the Actual Frequencies vs
Standard Requirements Table on page 5 and the
Control Register A Description below for details on the
control registers. The IRQ/CP pin can be programmed
to provide an interrupt request signal on validation of
DTMF signals, or when the transmitter is ready for
more data (burst mode only). The IRQ/CP pin is con­figured as an open-drain output device and as such
requires a pullup resistor (see the Single-Ended Input
Configuration on page 2).

Control Register B Description

Bit Name Function Description

b0 BURST Burst mode A logic 0 enables the burst mode. When this mode is selected, data corresponding to the desired DTMF

tone pair can be written to the transmit data register, resulting in a tone burst of a specific duration (see
the 12 AC Characteristics on page 9). Subsequently, a pause of the same duration is induced.
Immediately following the pause, the status register is updated indicating that the transmit data regis­ter is ready for further instructions, and an interrupt will be generated if the interrupt mode has been
enabled. Additionally, if call progress (CP) mode has bee enabled, the burst and pause duration is
increased by a factor of two. When the burst mode is not selected (logic 1), tone bursts of any desired
duration may be generated.

b1 TEST Test mode By enabling the test mode (logic 1), the IRQ/CP pin will present the delayed steering (inverted) signal

from the DTMF receiver.Refer to the Timing Diagrams onpage 11 (b3 waveform) for details concerning
the output waveform. DTMF modemust be selected (CRA b1=0) before test modecan be implemented.

b2 S/D Single/dual tone A logic 0 will allow DTMF signals to be produced. If single-tone generation is enabled generation

(logic 1), either now or column tones (low or high group) can be generated depending on the state of
b3 in control register B.

b3 C/R Column/row tones When used in conjunction with b2 (above), the transmitter can be made to generate single-row or sin-

gle-column frequencies. A logic 0 will select row frequencies and a logic 1 will select column frequen­cies.

Staus Register Description

Bit Name Status Flag Set Status Flag Cleared

b0 IRQ Interrupt has occurred. Bit one (b1) Interrupt is inactive. Cleared after

and/or bit 2 (b2) is set.status register is read.

b1 Transmit data register empty Pause duration has terminated and transmitter Cleared after status register is read or

(burst mode only) is ready for new data. when not in burst mode.

b2 Receive data register full. Valid data is in the receive data register. Cleared after status register is read.
b3 Delayed Steering Set on valid detection of the absence of a Cleared on detection of a valid DTMF

DTMF signal. signal.

b3 b2 b1 b0

RSEL IRQ CP/DTMF TOUT

M-8888

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Rev. 1

Common Crystal Connection

RS0 RD WR Function

0 1 0 Write to transmitter
0 0 1 Read from receiver
1 1 0 Write to control register
1 0 1 Read from status register

Internal Register Functions

CRA Bit Positions

b3 b2 b1 b0

C/R S/D TEST BURST

CRB Bit Positions

Equations

Application Circuit (Single-Ended Input)

DC Characteristics

Parameter Symbol Min Typ* Max Units

Operating supply voltage V

DD

4.75 5.0 5.25 V

Operating supply current I

DD

-1015mA

Power consumption P

O

- 50 78.75 mW

Inputs

High-level input voltage, OSC1 V

IHO

3.5 - - V

Low-level input voltage, OSC1 V

ILO

- - 1.5 V

Input impedance (@ 1 KHz), IN+, IN- R

IN

-10-MΩ

Steering threshold voltage V

TSt

2.2 2.3 2.5 V

Outputs

High-level output voltage (no load), OSC2 V

OHO

VDD- 0.1V - - V

Low-level output voltage (no load), OSC2 V

OLO

- - 0.1 V

Output leakage current (VOH= 2.4V), IRQ I

OZ

- 1.0 10.0 µA

V

REF

output voltage (no load) V

REF

2.4 - 2.7 V

V

REF

output resistance R

OR

- - 1.0 kΩ

Data Bus

Low-level input voltage V

IL

- - 0.8 V

High-level input voltage V

IH

2.0 - - V

Low-level output voltage (IOL= 1.6 mA) V

OL

- - 0.4 V

High-level output voltage (IOH= 400 µA) V

OH

2.4 - - V

Input leakage current (V

IN

= 0.4 to 2.4 V) I

IZ

- - 10.0 µA

All voltages referenced to VSSunless otherwise noted. VDD= 5.0 V ± 5%; fC= 3.579545 MHz; TA= -40°C to +85°C unless otherwise noted.

*Typical values are for use as design aids only, and are not guaranteed or subject to production testing.

Parameter Symbol Value

Power supply voltage

(VDD- VSS)VDD+ 6.0 V max

Voltage on any pin V

dc

VSS-0.3 V to VDD+ 0.3V

Current on any pin I

DD

10 mA max

Operating temperature T

A

-40°C to +85°C

Storage temperature T

S

-65°C to +150°C

Note: Exceeding these ratings may cause permanent damage. Functional operation under these
conditions is not implied.

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M-8888

Rev. 1

Absolute Maximum Ratings

Absolute Maximum Ratings are stress ratings. Stresses in
excess of these ratings can cause permanent damage to
the device. Functional operation of the device at these or
any other conditions beyond those indicated in the opera­tional sections of this data sheet is not implied. Exposure of
the device to the absolute maximum ratings for an extend­ed period may degrade the device and effect its reliability.

M-8888

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Rev. 1

AC Characteristics

Parameter Symbol Min Typ* Max Units

Receive signal conditions

Valid input signal levels - -29 - +1 dBm

(each tone of composite signal; Notes 1, 2, 3, 5, 6, 9) - 27.5 - 869 mV

RMS

Positive twist accept (Notes 2, 3, 6, 9) - - - 6 dB
Negative twist accept (Notes 2, 3, 6, 9) - - - 6 dB
Frequency deviation accept (Notes 2, 3, 5, 9) - ± 1.5% ± 2 Hz - - Nom.
Frequency deviation reject (Notes 2, 3, 5) - ± 3.5% - - Nom.
Third tone tolerance (Notes 2, 3, 4, 5, 9, 10) - - -16 - dB
Noise tolerance (Notes 2, 3, 4, 5, 7, 9, 10) - - -12 - dB
Dial tone tolerance (Notes 2, 3, 4, 5, 8, 9, 11) - - +22 - dB

Call progress

Lower frequency (@ -25 dBm) accept f

LA

- 320 - Hz

Upper frequency (@ -25 dBm) accept f

HA

- 510 - Hz

Lower frequency (@ -25 dBm) reject f

LR

- 290 - Hz

Upper frequency (@ -25 dBm) reject f

HR

- 540 - Hz

Receive timing

Tone present detect time t

DP

51114ms

Tone absent detect time t

DA

0.5 4 8.5 ms

Tone duration accept (the Timing Diagrams on page 10) t

REC

--40ms

Tone duration reject (the Timing Diagrams on page 10) t

REC

20 - - ms

Interdigit pause accept (the Timing Diagrams on page 10) t

ID

--40ms

Interdigit pause reject (the Timing Diagrams on page 10) t

DO

20 - - ms

Delay St to b3 t

PStb3

-13-µs

Delay St to RXO-RX

3

t

PStRX

-8-µs

Transmit timing

Tone burst duration (DTMF mode) t

BST

50 - 52 ms

Tone pause duration (DTMF mode) t

PS

50 - 52 ms

Tone burst duration (extended, call progress mode) t

BSTE

100 - 104 ms

Tone pause duration (extended, call progress mode) t

PSE

100 - 104 ms

Tone output

High group output level (RL= 10 KΩ)V

HOUT

-6.1 - -2.1 dBm

Low group output level (RL= 10 KΩ)V

LOUT

-8.1 - -4.1 dBm

Pre-emphasis (RL= 10 KΩ)dB

P

023dB
Output distortion (RL= 10 kΩ, 3.4 KHz bandwidth) THD - -25 - dB
Frequency deviation (f = 3.5795 MHz) f

D

- ± 0.7 ± 1.5 %

Output load resistance R

LT

10 - 50 kΩ

Microprocessor interface

RD, WR low pulse width t

CL

200 - - ns

RD, WR high pulse width t

CH

180 - - ns

RD, WR rise and fall time tR, t

F

--25ns

Address hold time t

AH

10 - - ns

Address setup time t

AS

23 - - ns

Data hold time (read) t

DHR

22 - - ns

RD to valid data delay (200 pF load) t

DDR

- - 150 ns

Data setup time (write) t

DSW

45 - - ns

Data hold time (write) t

DHW

10 - - ns

Input capacitance, D0-D3 C

IN

-5-pF

Output capacitance, IRQ /CP C/

OUT

-5-pF

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M-8888

Rev. 1

Electrical Characteristics - Gain Setting Amplifier

Parameter Symbol Min Typ* Max Units

Input leakage current (VSS≤ VIN≤ VDD)I

IN

- 100 - nA

Input resistance R

IN

-10 -MΩ

Input offset voltage V

OS

-25 -mV
Power supply rejection (1 KHz) PSRR - 60 - dB
Common mode rejection (-3.0 V≤ VIN≤ 3.0V) CMRR - 60 - dB
DC open-loop voltage gain A

VOL

-65 -dB
Unity gain bandwidth BW - 1.5 - MHz
Output voltage swing (RL≥ 100 KΩ to VSS)VO- 4.5 - V

PP

Maximum capcitive load, GS C

L

- 100 - pF
Maximum resistive load, GS R

L

-50 -kΩ

Common mode range (no load) V

CM

- 3.0 - V

PP

All voltages referenced to VSSunless otherwise noted. VDD= 5.0V ± 5%; VSS= 0 V; fC= 3.579545 MHz; TA= -40°C to +85°C
*Typical values are for use as design aids only, and are not guaranteed or subject to production testing.

Timing Diagrams

AC Characteristics (Continued)

Parameter Symbol Min Typ* Max Units

DTMF Clock

Crystal clock frequency f

C

3.5759 3.5795 3.5831 MHz

Clock input rise time (external clock) t

LHCL

- - 110 ns

Clock input fall time (external clock) t

HLCL

- - 100 ns

Clock input duty cycle (external clock) DC

CL

40 50 60 %

Capacitive load, OSC2 C

LO

--30pF

Voltages referenced to VSSunless otherwise noted. VDD= 5.0V ± 5%; VSS= 0 V; fC= 3.579545 MHz; TA= -40°C to +85°C
*Typical values are for use as design aids only and are not guaranteed or subject to production testing.
Notes:

1. dBm = decibels above or below a reference power of 1 mW into a 600 Ω load.

2. Digit sequence consists of all 16 DTMF tones.

3. Tone duration = 40 ms. Tone pause = 40 ms.

4. Nominal DTMF frequencies are used.

5. Both tones in the composite signal have an equal amplitude.

6. The tone pair is deviated by ± 1.5% ± 2 Hz.

7. Bandwidth limited (3 kHz) Gaussian noise.

8. The precise dial tone frequencies are 350 and 440 Hz (± 2%).

9. For an error rate of less than 1 in 10,000.

10. Referenced to the lowest amplitude tone in the DTMF signal.

11. Referenced to the minimum valid accept level.

M-8888

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Rev. 1

Test Loads

Timing Diagrams

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M-8888

Rev. 1

Explanation of Events

(A) Tone bursts detected, tone duration invalid, RX Data Register not updated.
(B) Tone #n detected, tone duration valid, tone decoded and latched in RX Data Register.
(C) End of tone #n detected, tone absent duration valid, RX Data Register remain latched until next valid tone.
(D) Tone #n + 1 detected, tone duration valid, tone decoded and latched in RX Data Register.
(E) Acceptable dropout of tone #n + 1, tone absent duration invalid, RX Data Register remain latched.
(F) End of tone #n + 1 detected, tone absent duration valid, RX Data Register remain latched until next valid tone.

Explanation of Symbols

V

IN

DTMF composite input signal.
ESt Early steering output. Indicates detection of valid tone frequencies.
St/GT Steering input/guard time output. Drives external RC timing circuit.
RX0-RX

3

4-bit decoded data in receive data register.
b3 Delayed steering output. Indicates that valid frequencies have been present/absent for the

required guard time, thus constituting a valid DTMF signal.
b2 Output enable (input). A low level shifts Q1 - Q4 to its high impedance state.
IRQ /CP Interrupt is active indicating that new data is in the RX data register. The interrupt is cleared

after the status register is ready.
t

REC

Maximum DTMF signal duration not detected as valid.
t

REC

Minimum DTMF signal duration required for valid recognition.
t

ID

Minimum time between valid DTMF signals.
t

DO

Maximum allowable dropout during valid DTMF signal.
t

DP

Time to detect the presence of valid DTMF signals.
t

DA

Time to detect the absence of valid DTMF signals.
t

GTP

Guard time, tone present.
t

GTA

Guard time, tone absent.

Tolerances

Inches Metric (mm)

Min Max Min Max

A .093 .104 2.35 2.65

A1 .004 .012 .10 .30

b .013 .020 .33 .51
D .496 .512 12.60 13.00
E .291 .299 7.39 7.59
e .050 BSC 1.27 BSC
H .394 .419 10.00 10.65
L .016 .050 .40 1.27

M-8888

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13

Rev. 1

Package Dimensions

Tolerances

Inches Metric (mm)

Min Max Min Max

A - .210 - 5.33

A1 .015 - .38 -

b .014 .022 .36 .56

b2 .045 .070 1.14 1.78

C .008 .014 .20 .36
D .980 1.060 24.89 26.92
E .300 .325 7.62 8.26

E1 .240 .280 6.10 7.11

e .100 BSC 2.54 BSC

ec 0° 15° 0° 15°

L .115 .150 2.92 3.81

Dimensions

mm

(inches)

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Clare, Inc. makes no representations or warranties with respect to
the accuracy or completeness of the contents of this publication
and reserves the right to make changes to specifications and
product descriptions at any time without notice. Neither circuit
patent licenses nor indemnity are expressed or implied. Except as
set forth in Clare’s Standard Terms and Conditions of Sale, Clare,
Inc. assumes no liability whatsoever, and disclaims any express or
implied warranty, relating to its products including, but not limit­ed to, the implied warranty of merchantability, fitness for a partic­ular purpose, or infringement of any intellectual property right.

The products described in this document are not designed,
intended, authorized or warranted for use as components in sys­tems intended for surgical implant into the body, or in other appli­cations intended to support or sustain life, or where malfunction
of Clare’s product may result in direct physical harm, injury, or
death to a person or severe property or environmental damage.
Clare, Inc. reserves the right to discontinue or make changes to its
products at any time without notice.

Specification: DS-M8888-R1
©Copyright 2001, Clare, Inc.
All rights reserved. Printed in USA.
7/26/01