EL6215 pdf datasheet (3-Channe

The EL6215 is a high-performance
three channel laser driver that
provides controlled current to a
grounded laser diode. Write channels 2 and 3 should be
used as the write channels, 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).