T0820

The T0820 is a laser diode driver for the operation of a grounded laser diode forwritable optical drives. T0820 includes four channels for four different optical power levelswhich are controlled by a separate IC. The read channel generates a continuousoutput level whereas channels 2 to 4 are provided as write channels with very fastswitching speeds. Write current pulses are enabled when a "low" signal is applied tothe NE pins. All channels are summed together at the IOUT pin. Read channel andchannel 2 can contribute up to 150 mA and channels 3 and 4 up to 200 mA to the totaloutput current of up to 300 mA. A total gain of 100 is provided between each referencecurrent input and the selected output. Although the reference inputs are current inputsvoltage control is possible by using external resistors. Frequency and swing of T0820 can be setby two external resistors. Oscillation is enabled by a "high" at the ENOSC pin. Com-plete output current and oscillator switch-off is achieved by a `low' at the ENABLEinput.