EL6224

   The EL6224 is a high performance three-channel laser driver that provides controlled current to a grounded laser diode. 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 I_OUT 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 I_IN pin (virtually ground). The current seen at this pin is then amplified to become a current source at pin I_OUT.

   An on-chip 600MHz oscillator EL6224 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 R_FREQ and R_AMP (see graphs in this datasheet for further explanation).

   Output current pulses EL6224 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 I_OUT shutoff is also achieved by holding the ENABLE pin low, which will override all other control pins.

   The external resistors EL6224 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 I_IN pin can be biased from a current DAC or other current source.