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11-25
11-25
In normal mode when Tuned is going �High� the channel data should be transmitted to the synthesizer to protect the receiver in case of hang-up situations.
3740
+5V
Muting The mute of the receiver is controlled by the IF receiver part but can be overiden by the microcontroller. The mute action initiated by the microcontroller is necessary during channel switching and in the standby mode. Muting has priority on all other main tasks. The hardware Mute is the result of an AND function between the �Tuned� and �Stereo� information. The Tuned information can be read by the microcontroller ( pin 2). The same pin (pin 2) has to be put in output mode to activate the microcontroller initiated Mute. This Mute must be used during the frequency setting and during the standby mode. Powersave mode
MUTE
CL36532008_086.eps 290403
DC-references and supply: +/- 15 Vdc preamp supply: The supply for the preamp is made by using a derived +/-15 Vdc from main power supply +/- 29.5 Vdc. Doing so assures a good symmetrical start-up on the power lines of the preamp, this suppresses possible plops.This supply is 15V for all operating conditions, except power save standby.
+/- 29.5 Vdc main supply: Will be switched off when the unit goes into power save-mode. See circuitry around 7107 and 7106. + 10Vdc receiver supply: Is always present, receiver stays always active Note that all supplies have the same ground reference.
100K BZX384-C5V1
BAS316
Mute circuitry: In normal operating circumstances, the voltage on the- �mode� pin of the amplifier IC7101 will be 4V5. This is the MUTE_AMPn signal.
+10V +10V
The main supply can be switched off with the �powersave� control line to reduce the current consumption. The microcontroller is always powered by the power supply. All other electronics can be put into powersave mode. After approx. 10 minutes of no �Tuned� signal the receiver goes into powersave mode. Once in powersave mode, the receiver is operated in �listen-sleep� mode to reduce the average current consumption. Power supply The board is having a low drop voltage regulator 7790, which has an output voltage of 8 Vdc. The 5 V supply for the micro controller is extracted from the 10 Vdc input supply via a zenerdiode 6751. The 5 Vdc supply of the synthesizer is extracted from transistor 7606. The powersave signal is also provided to the connector for the amplifier and for AV via the amplifierboard the SMPS is controlled.
6 1
+10V 3151 47K
6100 3133 47K BAS316 7104 BC847B
F127
MUTE_RX
7112 BC847B 3153 10K +10V +10V
Frequency setting Frequency setting is necessary when the 4-position slide switch is changed. In an internal look-up table the 4 required frequencies for the local oscillator are stored. The output towards the synthesiser chip in the frontend is in I²C form. The synthesizer is the only device on the bus. During frequency setting the Mute is active. Scanning of the channel switch should occur within every 250 milliseconds in any mode.
The AV-version of RX Amplifier board
3146 MUTE_WIRED
General: The amplifier module is intended to deliver 2 x 50 Watts into 8 ohm speakers. Speakers are connected through �easy-fit� connectors. See amplifier blockdiagram.
W
AUDIO OUTPUT AMPLIFIER +10V
10K
7108 BC847B
10u
BZX79-C2V7 BAS316
16V
2152
560K
6106 6103
10K 3148
OPTION
CL36532008_108.eps 290403
+ Analog sensitivity 1.4Vrms 7100-D,7100-A F111
1106 1 2 3 4 5 6 7
3144 F135 F137 F138 F139 +10V F140 F142 F144 3117 (active high) MUTE POWERSAFE (active high) sensitivity 2.5Vrms L R
This signal is coming from zener 6101 via diode 6100. Transistor 7104 and 7107 are not saturated at that moment. When the receiver generates a �mute� (MUTE_RX = 4Vdc on pin 6 of connector 1106) then 7104 saturates, diode 6100 blocks and the level on pin 6 -of IC 7101 becomes 2V1. The signal is now formed by zener 6106 via diode 6103. All DC references stay as they were; the class D keeps on oscillating, the led stays green but no sound is produced on the outputs. The control line STBY_OUT (connector 1107-pin 3) to the power supply stays low. When the receiver goes into powersavemode (= after 10 minutes no signal from the AV set), STANDBY signal is high; then the circuitry around 7107 pulls down the mode line of the amplifier to nearly 0V via the MUTE_AMPn signal. (Note that the mute line from the receiver is also high under this condition). The amplifier is completely in standby mode, the oscillator in amplifier IC 7101 stops and all internal references are disabled. The led red will be on, while green is off. At the same moment transistor 7106 is not saturated anymore and the control line towards the switched mode power-supply becomes high. This switches off the main +/- 29.5Vdc supply and the whole unit comes in a real power save mode. 7112 helps to pull down the
6108 3135 BAS316 560K 3129 2K2 6107 BAS316
mute line of the amplifier-chip 7101 as fast as possible to avoid plops at this transition. When the receiver detects a valid signal from the AV set, this power-save-line becomes continuously low, and after a small time (2152, 3143, 3147), 7104 is off. At the same moment the mute line becomes low and the amplifier is enabled again. Also the control line (connector 1107-pin 3) to the power supply becomes low, thus starting up the main +/- 29.5 Vdc supply Amplifier The amplifier TDA8920TH operates on +/-29.5 Vdc and can deliver 2 x 50 Watts into 8 ohm loads. Using the very efficient class D - technology, it minimizes the dissipation. The class - D chip runs on a ± 300kHz oscillator, therefore a 12dB / octave output filter is needed (coil 5104 and 5105, and capacitor 2122 and 2125). Input signals are 180° phase shifted by 7100-C and 7100-D, ( the effect - speakers have to be in phase with left and right main speakers, otherwise bass reproduction will be poor) Input signals are filtered in the two-section high pass filter around 7100-B and 7100-A. The � 3 dB point is somewhere around 30Hz. Input sensitivity of the amplifier for maximum output: typical 1.4V rms
3126 7104 MUTE CONTROL
7100-C,7100-B Temperature protection 6100 6101 C5V1 7105,7108 WIRED MUTE DRiVER 7107 POWER SAFE CONTROL 6106 C2V7 7110 +29,5V "+Power" "ON" LED DRIVER F124 GREEN 6109 6103 MUTE_AMPn F127 Mode mute OSC
Figure 1-27 Block diagram amplifier The crossover of the built-in high pass � filter will be around 30Hz. This eliminates sub-bass info going to the surround speakers. The amplifier uses �class D� amplifier-chip TDA8920. Additionally, the module is featured with a 2-colour indicator, green indicates the active state while red is standby. There is also an on-board 10 Vdc supply conditioning, specially intended for the TX receiver.
