ST7538PTR STMicroelectronics, ST7538PTR Datasheet - Page 15

• Manufacturer Part Number: ST7538PTR
• Manufacturer: STMicroelectronics

Specifications of ST7538PTR

• Main Category: Single Chip
• Power Supply Type: Analog/Digital
• Operating Supply Voltage (typ): 5/9/12V
• Operating Supply Voltage (min): 4.75/7.5V
• Operating Supply Voltage (max): 5.25/12.5V
• Supply Current: 5/370mA
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Pin Count: 44
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Compliant

■
Figure 12. CD_PD Timing during RX
Figure 13. Receiving Path Block Diagram
CD_PD
Carrier/Preamble Detection
The Carrier/Preamble Block is a digital Frequency detector Circuit.
It can be used to manage the MAINS access and to detect an incoming signal.
Two are the possible setting:
- Carrier Detection
- Preamble Detection
CARRIER DETECTION: The Carrier/Preamble detection Block notifies to the host controller the
presence of a Carrier when it detects on the RAI Input a signal with an harmonic component close to
the programmed Carrier Frequency. The CD_PD signal sensitivity is identical to the data reception
sensitivity (0.5mVrms Typ. in Normal Sensitivity Mode).
The CD_PD line is forced to a logic level low when a Carrier is detected.
PREAMBLE DETECTION: The Carrier/Preamble detection Block notifies to the host controller the
presence of a Carrier modulated at the Programmed Baud Rate for at least 4 Consecutive Symbols
(“1010” or “0101” are the symbols sequences detected).
CD_PD line is forced low till a Carrier signal is detected and PLL is in the lock-in range.
To reinforce the effectiveness of the information given by CD_PD Block, a digital filtering is applied on
Carrier or Preamble notification signal (See Control Register Paragraph). The Detection Time Bits in the
Control Register define the filter performance. Increasing the Detection Time reduced the false
notifications caused by noise on main line. The Digital filter adds a delay to CD_PD notification equal to
the programmed Detection Time. When the carrier frequency disappears, CD_PD line is held low for a
period equal to the detection time and then forced high.
CLR/T
RxD
BU
3
8
1
9
Bit 3,4 &14-21
PLL
Bit 9 & 10
Low Pass
CD_PD
Low Pass
DIGITAL
RAI
FILTER
Bit 3,4
DETECTION
PREAMBLE
DEMODULAOR
Bit 12 & 13
CARRIER/
Bit 3,4
FSK
T
DCD
T
Band Pass
IF FILTER
CD
Carrier Detection
LOCAL
MIXER
Bit 0 -2
OSC
Band Pass
CHANNEL
FILTER
Bit 0-2
D03IN1418
CONTROL
BAND
GAIN
USE
IN
AGC
31
RXFO
PRE-FILTER
Band Pass
Bit 23
D03IN1419
ST7538
32
15/30
RAI