ST7538Q STMicroelectronics, ST7538Q Datasheet - Page 27

• Manufacturer Part Number: ST7538Q
• Description: IC TXRX FSK POWER LINE 44-TQFP
• Manufacturer: STMicroelectronics
• Type: Transceiverr

Specifications of ST7538Q

• Number Of Drivers/receivers: 1/1
• Voltage - Supply: 4.75 V ~ 5.25 V
• Mounting Type: Surface Mount
• Package / Case: 44-TQFP Exposed Pad, 44-eTQFP, 44-HTQFP, 44-VQFP
• For Use With: 497-5484 - BOARD EVAL ST7538 PWR LINE TXRX
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Protocol: -
• Other names: 497-5525

ST7538Q
5.8.1
Automatic Level Control (ALC)
The Automatic Level Control Block (ALC) is a variable gain amplifier (with 32 non linear
discrete steps) controlled by two analog feed backs acting at the same time. The ALC gain
range is 0dB to 30 dB and the gain change is clocked at 5KHz. Each step increases or
reduces the voltage of 1dB (Typ).
Two are the control loops acting to define the ALC gain:
●
If Vsense < VCL
If VCL
If Vsense > VCL
●
If V(CL) < CCL
If CCL
If V(CL) > CCL
Figure 14
Figure 14. Voltage and current feedback external interconnection example
The Voltage control loop acts to keep the Peak-to-Peak Voltage constant on Vsense.
The gain adjustment is related to the result of a peak detection between the Voltage
waveform on Vsense and two internal Voltage references. It is possible to protect the
Voltage Control Loop against noise by freezing the output level (see
Output voltage level freeze on page
The Current control loop acts to limit the maximum Peak Output current inside
ATOP1 and ATOP2.
The current control loop acts through the voltage control loop decreasing the Output
Peak-to-Peak Amplitude to reduce the Current inside the Power Line Interface.
The current sensing is done by mirroring the current in the High side MOS of the Power
Amplifier (not dissipating current Sensing). The Output Current Limit (up to
400mApeak), is set by means of an external resistor (R
PAVss. The resistor converts the current sensed into a voltage signal. The Peak current
sensing block works as the Output Voltage sensing Block:
TH
TH
- VCL
- CCL
shows the typical connection of Current an Voltage control loops.
TH
TH
HYST
HYST
TH
TH
+ CLC
- CCL
+ VLC
ALC
- VCL
< Vsense < VCL
< V(CL) < CCL
CURRENT
VOLTAGE
HYST
HYST
LOOP
LOOP
HYST
HYST
80 pF
D03IN1421
TH
TH
+ CCL
+ VCL
ATOP/ATO
Vsense
CL
AVss
38).
5.6nF
HYST
RCL
HYST
The next gain level is decreased by 1 step
The next gain level is decreased by 1 step
Voltage Control Loop Acting
The next gain level is increased by 1 step
R1
R2
Vout
No Gain Change
No Gain Change
CL
) connected between CL and
Functional description
Section 6.6:
VCL
VCL
TH
CCL
HYST
1.865V (Typ)
CCL
TH
HYST
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