EL6839
Dual 4-Channel Laser Driver with Oscillator and LVDS

Key Features

• Two channels for CD or DVD
• Voltage-controlled output current source requiring one external set resistor per channel
• LVDS interface
• Rise time = 0.8ns
• Fall time = 0.8ns
• Channel 2 to 250mA max
• Channel 3 to 150mA max
• Channel 4 to 100mA max
• External 100Ω LVDS termination
• On-chip oscillator with frequency and amplitude control by use of external resistors to ground
• Oscillator frequency to 600MHz
• Oscillator amplitude to 100mA_P-P
• Single +5V supply (±10%)
• Chip ENAs for power savings
• Pb-free available (RoHS compliant)

Description

The EL6839 is a high performance, dual output, laser driver for writeable DVD drives. The ENA pin enables the chip, while the SEL1 pin selects the I_OUT pin. Various waveforms can be generated where the amplitude is determined by the currents flowing into I_INR, I_IN2, I_IN3, and I_IN4. The timing is determined by the signals at WEN2-WEN2B, WEN3-WEN3B, and WEN4-WEN4B. The oscillator is enabled when OSEN is high. The amplified I_INR current of the selected channel is enabled when the ENA pin is high. The total output current is the sum of the read current, the enabled write currents, and the oscillator current when enabled.

Usually a voltage DAC will drive a resistor that is in series with the I_INR, I_IN2, I_IN3, and I_IN4 input. The resistor allows the user to optimize the current gain for each channel.

WEN2-WEN2B, WEN3-WEN3B and WEN4-WEN4B are LVDS input pins with 100Ω external termination. Output write current pulses are enabled when a high is applied to the WEN2-WEN2B, WEN3-WEN3B, or WEN4-WEN4B pin. The write current will flow to the selected output. When SEL1 is high I_OUT1 is selected. WENRB enables read and oscillator current when low.

The RF oscillators frequency is determined by R_FREQ1 or R_FREQ2, and its amplitude by R_AMP1 or R_AMP2.

Applications

• Super combo drives
• DVD drives