ST75C530 Datasheet, PDF (79/84 Pages) STMicroelectronics – SUPER INTEGRATED DEVICESWITH DSP, AFE & MEMORIES FORTELEPHONY,MODEM, FAXOVERINTERNET& POTSLINES

ST75C530 - ST75C540
XVIII - PCB DESIGN GUIDELINES
Performances of the FAX modem depends on the
ST75C530/540 intrinsic performances and on the
proper PC board layout.
All aspects of the proper engineering practices, for
PC board design, are beyond the scope of this
paragraph.
We recommend the following points :
- in a 4-layer PC board : Separated digital ground
and analog ground, connected together at one
point, as close as possible to the ST75C530/540,
- in a 2-layer PC board : Provide a ground grid in all
spacearoundand under componentson bothsides
of the band and connect to avoid small islands,
- both AGNDR and AGNDT must be connected
with very low impedance to a single point, (see
Chapter I.6, Power Supply),
- the four 2.2nF capacitors connected to the RxA
and MIC1, MIC2, MIC3 Pins must be as close as
possible to them,
- thetwo100nFcapacitorsconnectedtotheVREFP and
VREFN pins must be as close as possible to them,
- analog and digital supplies must be connected
together,at a single point, as close as possibleto
the chip.
XIX - APPENDIX A : MODES OF OPERATION
Figure 49 : Tone Mode (TONE)
DUAL
RAM
INTERFACE
DTMF
DETECTOR
16 TONE
DETECTORS
4 TONE
DETECTORS
V.21 FLAG
DETECTOR
RING
DETECTOR
4 TONES
GENERATOR
ATT_TX
DAC
DG
ADC
ATT_SPK
ATT_LOC
DAC
MUTE
MUTE
[0..-30]dB
Step 3dB
MUTE
MUTE
Programmable
Attenuation
Addition
of Signals
DG
Automatic
Gain
ADC
Figure 50 : Tone Mode with Caller ID (TONECID)
DUAL
RAM
INTERFACE
DTMF
DETECTOR
4 TONES
GENERATOR
ATT_TX
DAC
6 TONE
DETECTORS
DG
ADC
4 TONE
DETECTORS
V.21 FLAG
DETECTOR
UART
V.23
DEMODULATOR
ATT_SPK
ATT_LOC
DAC
RING
DETECTOR
MUTE
MUTE
[0..-30]dB
Step 3dB
MUTE
MUTE
Programmable
Attenuation
Addition
of Signals
DG
Automatic
Gain
ADC
TxA1
15
14
HYBRID
Line
TxA2
11
RxA
1
2 _SPK1
76
SPK3
77
78
79
SPK2
9
MIC2
8
MIC1
10 MIC3
TxA1
15
14
HYBRID
TxA2
11
RxA
1
2
SPK1
76
SPK3
77
78
79
SPK2
9
MIC2
8
MIC1
10 MIC3
Line
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