EL6249C

Features:

• "Shrink-Small" Outline Package
• Voltage controlled output current source, requiring one external set resistor per channel
• Auto Oscillator On-Off with OUTEN Signals
• Rise time = 0.8ns
• Fall time = 0.8ns
• On chip oscillator with frequency and amplitude control by use of external resistors to ground
• Oscillator to 500MHz
• Oscillator to 100mA pk/pk
• Single +5V supply (±10%)
• Current amplification = 100
• Disable feature for power-up protection and power savings
• CMOS control signals



Application

• CD-RW applications
• Writable optical drives
• Laser diode current switching



Pinout




Description

   The EL6249C is a four channel laser diode current amplifier that provides controlled current to a grounded laser diode. Channels 2, 3, and 4 should be used as the write channels, with switching speeds of approximately one nanosecond rise/fall time. All 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 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.

   Output current pulses EL6249C 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 the OUTEN control pins.

   An on-chip 500MHz oscillator EL6249C is provided to allow output current modulation when in read mode. The oscillator is enabled when the OSCEN pin is held high. If any of channels 2, 3, or 4 are active, the oscillator is switched off. 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).

   The external IIN resistors EL6249C 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.