EL6259

The EL6259C is a low noise four channel laser diode current amplifie that provides controlled current to a grounded laser diode. The fou amplifiers can provide up to 150 mA per channel of DC or pulsed cur rent. Channels 2, 3, and 4 must be used as the write channels, with switching speeds of approximately one nanosecond rise/fall time. Al four 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 volt age applied to an external resistor which converts the voltage into a current at the I_IN pin. The current seen at this pin is then amplified by 100X to become a current source at pin I_OUT.

An on-chip 500 MHz oscillator EL6259C is provided to allow current modula tion when in the read mode. This is turned on when the EOSC pin is held high (floating not recommended). Complete control of amplitude and frequency is set by two external resistors connected to ground a pins RFREQ and RAMP (see graphs in this data sheet for furthe explanation).

Output current pulses EL6259C are enabled when an 'L' signal is applied to the OE pin. No output current flows when OEis 'H', and additional lase diode protection is provided since the OE input will float high when open. Complete I_OUT shut-off is also achieved by holding the CE pin low, which will override the OE control pins.

The external resistors EL6259C 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.