75T2091 DTMF Transceivers Datasheet

75T2091 Datasheet, PDF, Equivalent


Part Number

75T2091

Description

DTMF Transceivers

Manufacture

TDK

Total Page 9 Pages
Datasheet
Download 75T2091 Datasheet


75T2091
DESCRIPTION
TDK Semiconductor’s 75T2089/2090/2091 are
complete Dual-Tone Multifrequency (DTMF)
Transceivers that can both generate and detect all
16 DTMF tone-pairs. These ICs integrate the
performance-proven 75T202 DTMF receiver with a
DTMF generator circuit.
The DTMF receiver electrical characteristics are
identical to the standard 75T202 device
characteristics. The DTMF generator provides
performance similar to the Mostek MK5380, but with
an improved (tighter) output amplitude range
specification and with the addition of independent
latch and reset controls.
An additional feature of the 75T2090/2091 is
"imprecise" call progress detector. The detector
detects the presence of signals in the 305-640 Hz
band.
(continued)
75T2089/2090/2091
DTMF Transceivers
FEATURES
April 2000
DTMF Generator and Receiver on one-chip
Call progress detection (2090/2091 only)
Early detect output (2091 only)
DTMF Receiver exhibits excellent speech
immunity
Analog input range from -32 to -2 dBm
(ref 600)
Three-state outputs (4-bit hexadecimal) from
DTMF Receiver
AC coupled, internally biased analog input
Latched DTMF Generator inputs
DTMF output typ. -8 dBm (Low Band) and
-5.5 dBm (High Band)
Easy interface for microprocessor dialing
Uses inexpensive 3.579545 MHz crystal for
reference
Low-power 5 volt CMOS
BLOCK DIAGRAM
LIN
(2090/2091 only)
D7
D6
D5
D4
Vp
LATCH
Vp
RESET
DIN
XIN
DQ
DQ
DQ
DQ
CK
RS
X1
XOUT
XEN ATB
Vp
8
BANDSPLIT
FILTERS
INTERNAL
CLOCK
ENERGY
DETECTOR
Vp
DTMF
GENERATOR
CK Q
Vp D CLR
BANDPASS
FILTERS
BANDPASS
FILTERS
697
BS1 770
852
AMPLITUDE
DETECTORS
TIMING
CIRCUITRY
941
1209
BS2 1336
DV
STROBE
DV
F.F.
1477
1633
POWER REGULATOR
VOLTAGE
REF
OUTPUT
DECODER
AND
REGISTER
Vp Vn
DE
DET
(2090/2091 only)
DTMF
OUT
ED
(2091 only)
DV
D3
D2
D1
D0

75T2091
75T2089/2090/2091
DTMF Transceivers
DESCRIPTION (continued)
The 75T2091 also incorporates an early detect
function which is useful in multi-channel radio
scanning applications. The only external
components necessary for the 75T2089/2090/2091
are a 3.58 MHz “colorburst” crystal with a parallel 1
Mresistor. This provides the time base for digital
functions and switched-capacitor filters in the device.
No external filtering is required.
CIRCUIT OPERATION
RECEIVER
The DTMF Receiver in the 75T2089/2090/2091 detects
the presence of a valid tone pair (indicating a single
dialed digit) on a telephone line or other transmission
medium. The analog input is pre-processed by 60 Hz
reject and band-splitting filters, then hard-limited to
provide Automatic Gain Control. Eight bandpass filters
detect the individual tones. The digital post-processor
times the tone durations and provides the correctly
coded digital outputs. The outputs will drive standard
CMOS circuitry, and are three-state enabled to facilitate
bus-oriented architectures.
DIN
This pin accepts the analog input. It is internally
biased so that the input signal may be AC coupled.
The input may be DC coupled as long as it does not
exceed the positive supply. Proper input coupling is
illustrated in Figure 1.
Vp Vp
VIN<VP
VIN>VP
8
DIN
10 pF
>100 k
0.01 µF
DIN
8
10 pF
>100 k
GND
GND
FIGURE 1: Input Coupling
The IC is designed to accept sinusoidal input
waveforms but will operate satisfactorily with any
input that has the correct fundamental frequency
with harmonics greater than -20 dB below the
fundamental.
CRYSTAL OSCILLATOR
The IC contains an onboard inverter with sufficient
gain to provide oscillation when connected to a low-
cost television “colorburst” crystal. The crystal is
placed between XIN and XOUT in parallel with a
1Mz resistor, while XEN is tied high. Since the
switched-capacitor-filter time base is derived from
the crystal oscillator, the frequency accuracy of all
portions of the IC depends on the time base
tolerance. The DTMF Receiver frequency response
and timing is specified for a time base accuracy of at
least =0.005%. ATB is a clock output with the
frequency of 1/8 of crystal. Other devices may use
the same frequency reference by tying their ATB
pins to the ATB of a crystal connected device. XIN
and XEN of the auxiliary devices must then be tied
high and low respectively, XOUT is left floating.
XOUT is designed to drive a resonant circuit only
and is not intended to drive additional devices. Ten
devices may run off a single crystal-connected
transceiver as shown in Figure 2.
XIN
ATB
XOUT
VP
75T20XX
XEN
ATB
XIN Connected to VP
75T20XX
XEN
Up to 10 Devices
FIGURE 2: Crystal Connections
2


Features DESCRIPTION TDK Semiconductor’s 75T20 89/2090/2091 are complete Dual-Tone Mul tifrequency (DTMF) Transceivers that ca n both generate and detect all 16 DTMF tone-pairs. These ICs integrate the per formance-proven 75T202 DTMF receiver wi th a DTMF generator circuit. The DTMF receiver electrical characteristics are identical to the standard 75T202 devic e characteristics. The DTMF generator p rovides performance similar to the Most ek MK5380, but with an improved (tighte r) output amplitude range specification and with the addition of independent l atch and reset controls. An additional feature of the 75T2090/2091 is "impre cise" call progress detector. The detec tor detects the presence of signals in the 305-640 Hz band. (continued) 75 T2089/2090/2091 DTMF Transceivers FEAT URES April 2000 • DTMF Generator an d Receiver on one-chip • Call progres s detection (2090/2091 only) • Early detect output (2091 only) • DTMF Rece iver exhibits excellent speech immunity • Analog input range .
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