The EL6211 is a three-channel laser
diode current amplifier that provides
controlled current to a grounded laser
diode. Channels 2 and 3 should be used as the write
channels, with switching speeds of less than two
nanoseconds 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).
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 shutoff is also achieved by holding the
ENABLE pin low, which will override the OUTEN control
pins.
The external resistors allow the user to accurately and
independently set each amplifier transconductance by
applying a voltage to each resistor, without restriction on the
voltage range, thus ensuring broad voltage DAC
compatibility. Alternatively, the IIN pin can be biased from a
current DAC or other current source.