The EL6146 is a four channel laser
diode current amplifier that provides
controlled current to a grounded laser
diode. Channels 2, 3, and 4 must be used as the write
channels, with switching speeds of approximately one
nanosecond rise/fall time. All four 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 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 all other 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.