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PDF FX631 Data sheet ( Hoja de datos )
| Número de pieza | FX631 | |
| Descripción | Low-Voltage SPM Detector | |
| Fabricantes | CML | |
| Logotipo |  |
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CML Semiconductor Products
PRODUCT INFORMATION
FX631 Low-Voltage SPM Detector
Features
Detects 12kHz and 16kHz SPM
Frequencies
Low Power (3.0 VoltMIN <1.0mA)
Operation
High Speechband Rejection
Properties
Publication D/631/8 July 1998
Tone-Follower and Packet Mode
Outputs
Applications
Complex and/or Simple
Telephone Systems
Call-Charge/-Logging
Systems
XTAL/CLOCK
XTAL/CLOCK
OSCILLATOR
XTAL
CLOCK
OUT
CLOCK IN
SYSTEM
CLOCK
DIVIDERS
VSS
VDD
SYSTEM
(12kHz/16kHz)
SIGNAL
IN (-)
SIGNAL
IN (+)
AMP OUT
INPUT AMP
-
+
12kHz/16kHz
+20dB
VBIAS
TONE FOLLOWER
OUTPUT
TONE
FOLLOWER
LOGIC
LEVEL DETECTOR
32
1
DIVIDER
PERIOD
MEASURE
SYSTEM
PACKET
TONE
LOGIC
PACKET MODE
OUTPUT
FX631
Fig.1 Functional Block Diagram
Brief Description
The FX631 is a low-power, system-selectable
Subscriber Pulse Metering (SPM) detector to indicate
the presence, on a telephone line, of both 12kHz and
16kHz telephone call-charge frequencies.
Deriving its input directly from the telephone line,
input amplitude/sensitivities are component adjustable to
the user's national ‘Must/Must-Not Decode’
specifications via an on-chip input amplifier, whilst the
12kHz and 16kHz frequency limits are accurately
defined by the use of an external 3.579545MHz
telephone-system Xtal or clock-pulse input.
The FX631, which demonstrates high 12kHz and
16kHz performance in the presence of both voice and
noise, can operate from either a single or differential
analogue signal input from which it will produce two
individual logic outputs.
1. Tone Follower Output - A 'tone-following' logic
output producing a “Low” level for the period of a
correct decode and a “High” level for a bad
decode or NOTONE.
2. Packet (Cumulative Tone) Mode Output - To
respond and de-respond after a cumulative 40ms
of good tone (or NOTONE) in any 48ms period.
This process will ignore small fluctuations or
fades of a valid frequency input and is available
for µProcessor ‘Wake-Up’, Minimum tone
detection, NOTONE indication or transient
avoidance.
This system (12kHz/16kHz) selectable microcircuit,
which may be line-powered, is available in 16-pin plastic
DIL and surface mount SOIC and 24-pin plastic SSOP
packages.
1
1 page  
Application Information ......
Input Gain Calculation
The input amplifier, with its external circuitry, is
provided on-chip to set the sensitivity of the FX631 to
conform to the user's national level specification with
regard to ‘Must’ and ‘Must-Not’ decode signal levels.
With reference to the graphs in Figures 4 and 5, the
following steps will assist in the determination of the
required gain/attenuation.
Step 1
Draw two horizontal lines from the Y-axis (Signal
Levels (dB)).
The upper line will represent the required ‘Must’
decode level.
The lower line will represent the required ‘Must-
Not’ decode level.
Input Gain Components
With reference to the gain components shown in Figures
2 and 3.
The user should calculate and select external
components (R1, R2/C3, R3/C4, R4) to provide an amplifier
gain within the limits obtained in Steps 2 and 3.
Component tolerances should not move the gain-figure
outside these limits.
It is recommended that the designed gain is near the
centre of the calculated range. The graphs in Figures 4 and 5
are for the calculation of input gain components for an FX631
using a VDD of 3.3 (±0.1) or 5.0 (±0.5) volts respectively.
Use this area to keep a permanent record
of your calculated gains and components
Step 2
Mark the intersection of the upper horizontal line
and the upper sloping line; drop a vertical line from
this point to the X-axis (Amplifier Gain (dB)).
The point where the vertical line meets the X-axis
will indicate the MINIMUM Input Amp gain
required for reliable decoding of valid signals.
Step 3
Mark the intersection of the lower horizontal line
and the lower sloping line; drop a vertical line from
this point to the X-axis.
The point where the vertical line meets the X-axis
will indicate the MAXIMUM allowable Input Amp
gain.
Input signals at or below the ‘Must-Not’ decode
level will not be detected as long as the amplifier
gain is no higher than this level.
Select the gain components as described
opposite.
Implementation Notes
Aliasing
Due to the switched-capacitor filters employed in the
FX631, care should be taken, with the chosen external
components, to avoid the effects of alias distortion.
Possible Alias Frequencies:
12kHz Mode = 52kHz
16kHz Mode = 69kHz
If these alias frequencies are liable to cause problems and/or
interference, it is recommended that anti-alias capacitors are
employed across input resistors R1 and R4.
Values of anti-alias capacitors should be chosen so as to
provide a highpass cutoff frequency, in conjunction with R1
(R4) of approximately 20kHz to 25kHz (12kHz system) or
25kHz to 30kHz (16kHz system).
i.e. C = 1
2 x π x f0 x R1
When anti-alias capacitors are used, allowance must be
made for reduced gain at the SPM frequency (12kHz or
16kHz).
Microcircuit Protection
Telephone systems may have high d.c. and a.c. voltages
present on the line. If the FX631 is part of a host equipment
that has its own signal input protection circuitry, there will be
no need for further protection as long as the voltage on any
pin is limited to within VDD + 0.3V and
VSS -0.3V.
If the host system does not have input protection, or there
are signals present outside the device's specified limits, the
FX631 will require protection diodes at its signal inputs (+ and
-). The breakdown voltage of capacitors and the peak
inverse voltage of the diodes must be sufficient to withstand
the sum of the d.c. voltages plus all expected signal peaks.
Clock Out
The Clock Out pin is intended to drive the FX631 Clock In
pin only. It is not recommended that it be used to clock other
devices within the host equipment.
5
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| PDF Descargar | [ Datasheet FX631.PDF ] | |
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