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M-8880 데이터시트 PDF




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부품번호 M-8880 기능
기능 M-8880 DTMF Transceiver
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M-8880 데이터시트, 핀배열, 회로
M-8880 DTMF Transceiver
· Advanced CMOS technology for low power consump-
tion and increased noise immunity
· Complete DTMF transmitter/receiver in a single chip
· Standard 6500/6800 series 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
· No continuous f2 clock required, only strobe
· Applications include: paging systems, repeater sys-
tems/mobile radio, interconnect dialers, PBX systems,
computer systems, fax machines, pay telephones,
credit card verification
The M-8880 is a complete DTMF Transmitter/Receiver that fea-
tures adjustable guard time, automatic tone burst mode, call
progress mode, and a fully compatible 6500/6800 microproces-
sor interface. The receiver portion is based on the industry stan-
dard M-8870 DTMF Receiver, while the transmitter uses a
switched-capacitor digital-to-analog converter for
low-distortion, highly accurate DTMF signaling. Tone bursts can
be transmitted with precise timing by making use of the auto-
matic tone burst mode. To analyze call progress tones, a call
progress filter can be selected by an external microprocessor.
Figure 1 Pin Diagram
Functional Description
M-8880 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 6500/6800 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 opera-
tional amplifier and bias sources (VREF) for biasing the amplifier
inputs at VDD/2. Provisions are made for the connection of a
feedback resistor to the op-amp output (GS) for gain adjust-
40-406-00012, Rev. G
Figure 2 Block Diagram
Page 1
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M-8880 pdf, 반도체, 판매, 대치품
M-8880
detected if the CP mode has been selected (see Table 3). Fig-
ure 7 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 trig-
ger can be analyzed by a microprocessor or counter arrange-
ment 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.
Figure 7 Call Progress Response
DTMF Generator
The DTMF transmitter used in the M-8880 is capable of generat-
ing 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 accu-
racy. To specify a DTMF signal, data conforming to the encod-
ing format shown in Table 2 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 (fLOW and fHIGH) are re-
ferred to as low-group and high-group tones. Typically, the
high-group to low-group amplitude ratio (twist) is 2 dB to com-
pensate for high-group attenuation on long loops.
Operation: During write operations to the transmit data register,
4-bit 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 seg-
ment 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. 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 gener-
ated 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 accom-
plished by making use of the burst mode. The transmitter is ca-
pable 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 sta-
tus register, indicating that the transmitter is ready for more data.
The timing described is available when the DTMF mode has
been selected. However, when call progress (CP) mode is se-
lected, 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 requiring a nonstandard
burst/pause time, use a software timing loop or external timer.
This provides the timing pulses when the burst mode is disabled
by enabling and disabling the transmitter.
The M-8880 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 Table 4 for details.
Distortion Calculations: The M-8880 is capable of producing
precise tone bursts with minimal error in frequency (see Table
3). The internal summing amplifier is followed by a first-order
low-pass switched capacitor filter to minimize harmonic compo-
nents and intermodulation products. The total harmonic distor-
tion for a single tone can be calculated using Equation 1, (see
Figure 9) which is the ratio of the total power of all the extrane-
ous frequencies to the power of the fundamental frequency ex-
pressed 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 Figure 9).
Table 3 Actual Frequencies vs. Standard
Requirements
Active
Cell
L1
L2
L3
L4
H1
H2
H3
H4
Output Frequency (Hz)
Specified
Actual
697 699.1
770 766.2
852 847.4
941 948.0
1209
1215.9
1336
1331.7
1447
1471.9
1633
1645.0
% Error
+ 0.30
- 0.49
- 0.54
+ 0.74
+ 0.57
- 0.32
- 0.35
+ 0.73
40-406-00012, Rev. G
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M-8880 전자부품, 판매, 대치품
M-8880
Table 9 Status Register Description
BIT Name
Status Flag Set
Status Flag Cleared
b0 IRQ
Interrupt has occurred. Bi tone (b1) and/or bit 2 (b2) Interrupt is inactive. Cleared after status register is
is set.
read.
b1 Transmit data register Pause duration has terminated and transmitter is
empty (burst mode only) ready for new data.
Cleared after status register is read or 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 DTMF sig- Cleared on detection of a valid DTMF signal.
nal.
Table 10 Absolute Maximum Ratings
Parameter
Symbol
Value
Power supply voltage (VDD - VSS)
VDD
+ 6.0 V max
Voltage on any pin
Vdc VSS -0.3 V to VDD + 0.3 V
Current on any pin
IDD 10 mA max
Operating temperature
TA -40°C to +85°C
Storage temperature
TS -65°C to +150°C
Note: Exceeding these ratings may cause permanent damage. Functional operation under these conditions is not implied.
Table 11 DC Characteristics
Parameter
Symbol
Min
Typ*
Max Units
Operating supply voltage
Operating supply current
Power consumption
Inputs
VDD
IDD
PO
4.75
5.0 5.25
V
10 15 mA
50
78.75
mW
High-level input voltage, OSC1
Low-level input voltage, OSC1
Input impedance (@ 1 kHz), IN+, IN-
Steering threshold voltage
VIHO
3.5
V
VILO
— 1.5
V
RIN — 10 — M
VTSt
2.2
2.3
2.5
V
Outputs
High-level output voltage (no load), OSC2
Low-level output voltage (no load), OSC2
Output leakage current (VOH = 2.4V), IRQ
VREF output voltage (no load)
VREF output resistance
VOHO
VOLO
IOZ
VREF
ROR
VDD - 0.1V
2.4
1.0
0.1
10.0
2.7
1.0
V
V
µA
V
k
Data Bus
Low-level input voltage
VIL
— 0.8
V
High-level input voltage
VIH 2.0
V
Low-level output voltage (IOL = 1.6 mA)
VOL
— 0.4
V
High-level output voltage (IOH = 400 µA)
VOH
2.4
V
Input leakage current (VIN = 0.4 to 2.4 V)
IIZ — — 10.0 µA
All voltages referenced to VSS unless otherwise noted. VDD = 5.0 V ± 5%; fC = 3.579545 MHz; ΤA = -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.
40-406-00012, Rev. G
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부품번호상세설명 및 기능제조사
M-8880

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