The EL6173 is a high performance
three-channel laser driver that
provides controlled current to a
grounded laser diode. Write channels 2 and 3 can provide
up to 200mA per channel of DC or pulsed current, with
switching speeds of approximately one nanosecond rise/fall
time. All three channels are summed together at the IOUT
output, allowing the user to create multilevel waveforms in
order to optimize laser diode performance. The level of the
output current is set by an analog voltage applied to an
external resistor which converts the voltage into a current at
the IIN pin (virtually ground). The current seen at this pin is
then amplified to become a current source at pin IOUT.
An on-chip 500MHz oscillator is provided to allow output
current modulation when in any mode. This is turned on
when the OSCEN pin is held high. Complete control of
amplitude and frequency is set by two external resistors
connected to ground at pins RFREQ and RAMP (see graphs
in this data sheet for further explanation.)
Output current pulses are enabled when an ‘L’ signal is
applied to the OUTEN pin. No output current flows when
OUTEN is ‘H’ and additional laser diode protection is
provided since the OUTEN input will float high when open.
Complete IOUT shut-off is also achieved by holding the
ENABLE pin low, which will override all other control pins.
The EL6173 also includes a fast-settling APC amplifier
designed to interface directly with the front end monitor
diode and the sample-and-hold amplifier for read and write
power control. Its 100MHz bandwidth and 30ns settling time
enable up to 16X CD-RW design.