Site Contents
- Introduction
- Audio Data Format
- Interface Applications
- Hardware Specifications
- Data Transmission
- Digital-Analog Converter
- Resetting & Auto-Switching
- History & Characteristics
- Data & Cabling Details
- Coding Format
- Conversion Circuits
- Internal Connection
- External Connection
- Optical Output Circuit
- Transmission Line
Sponsors
SPDIF: Optical Output Circuit
TOSLINK Output
In a typical TOSLINK output circuit, TOSLINK transmitting module TOTX173 is used. In the +5v power source, a filter is made against digital noise by a 4.7 ohm resistor and 100nF capacitor. TTL signal is used. TOSLINK optical connections are in standard use for DVD players and satellite boxes. The TOSLINK optical output of a DVD player can be fed to a second receiver located in another room.
Cheap Optical SPDIF Output
TOSLINK Modules are available at a very low cost. Having in-built connector, their interface is much easy. TOSLINK SPDIF optical transmitter basically consists of a red LED that is coupled to the optic fibre. Building a basic output circuit requires only a red LED and a resistor. These are available at any electronic component shop. Basic idea of the circuit is feeding through a series current limiting resistor the digital data to the LED that need only 5-30 mA. LED is off when digital 0 is 0v and LED is on when digital 1 is +5v. The red LED to be used should have a typical wavelength of 660nm. For buffering the signal, a Hex converter may also be used. This holds good if the TTL/SPDIF output of the source device cannot handle a load of 20-30 mA that this circuit generates.
Optical TOSLINK Receiver
The circuit uses TTL output and TORX173. In the +5v power source, a filter against digital noise is made by 100 nF capacitor and 47 microhenry coil. TORX173 and TOTX173 are the optical receiver and transmitter modules used for SPDIF. TORX and TOTX are both highly active modules and compatible to CMOS/TTL logic.
Advantages Of TOSLINK
One does not have to deal with impedance at inputs and outputs at TOSLINK. Possibility of ground loop problem is also remote. TOSLINK is the best choice in a situation where receivers located at different rooms have to be fed.