Philips 7603 series, Service Manual

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Over Temperature protection
When the junction temperature exceeds the thermal shutdown temperature (typ. 140º C), the IC will disable the driver. When
the VCC voltage drops to UVLO, the VCC capacitor will be recharged to the V(start) level. If the temperature is still too high,
the VCC voltage will drop again to the UVLO level (Safe-Restart mode). This mode will persist until the junction temperature
drops 8 degrees typically below the shutdown temperature.
Mains dependent operation enabling level
To prevent the supply from starting at a low input voltage, which could cause audible noise, a mains detection is
implemented (Mlevel). This detection is provided via pin 8, that detects the minimum start-up voltage between 60 and 100 V.
As previous mentioned, the controller is enabled between 60 and 100 V.
An additional advantage of this function is the protection against a disconnected buffer capacitor (CIN). In this case, the
supply will not be able to start-up because the VCC capacitor will not be charged to the start-up voltage.
Control
Introduction
The microprocessor part of the UOC, has the complete control and teletext on board. User menu, Service Default Mode,
Service Alignment Mode and Customer Service Mode are generated by the µP. Communication to other ICs is done via the
I2C-bus.
I 2 C-Bus
The main control system, which consists of the microprocessor part of the UOC (7200), is linked to the external devices
(tuner, NVM, MSP, etc) by means of the I2C- bus. An internal I2C-bus is used to control other signal processing functions,
like video processing, sound IF, vision IF, synchronization, etc.
User Interface
The L8/M8 uses a remote control with RC5 protocol. The incoming signal is connected to pin 67 of the UOC. The 'Top
Control' keyboard, connected to UOC pin 80, can also control the set. Button recognition is done via a voltage divider.
The front LED (6691) is connected to an output control line of the microprocessor (pin 5). It is activated to provide the user
information about whether or not the set is working correctly (e.g., responding to the remote control, normal operation (USA
only) or fault condition).