EL6258C

Features:

• High-performance laser diode driver
• Voltage-controlled output current source requiring one external set resistor per channel
• Current-controlled output current source
• Rise time = 1.0ns
• Fall time = 1.1ns
• 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
• TTL/CMOS control signals
• Fast settling APC amplifier



Application

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


Pinout




Description

   The EL6258C is a high-performance three channel laser diode current amplifier that provides controlled current to a grounded laser diode. Channels 2 and 3 must 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. Each level of output current is set by an analog voltage applied to an external resistor which converts the voltage
into a current at the I_IN pins (virtually ground). The current seen at these pins is then amplified by 100X (150X on CH3) to become a current source at pin I_OUT.

   An on-chip 500MHz oscillator EL6258C is provided to allow current modulation when in the read mode. This is turned on when the OSCEN pin is held high (floating not recommended). Complete control of amplitude and frequency is set by two external resistors connected to ground at pins RFREQ and RAMP (see graphs for further explanation). The oscillator will also turn off whenever either of the OUTEN pins for channels 2 or 3 (the write channels) are low (see truth table).

   Output current pulses EL6258C are enabled when an 'L' signal is applied to the OUTEN pins. 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 shut-off is also achieved by holding the ENABLE pin low, which will override the OUTEN control
pins.

   The EL6258C also includes a fast settling APC amplifier designed to interface directly with the power monitor photodiode and the sampleand-hold amplifier, for read and write power control.