Features

Ω Termination

× 4 mm Package

Applications

1.

Description

The ATR0849 is a laser diode driver designed to operate two different grounded laser

diodes for DVD-RW/DVD+RW (650 nm) and CD-RW (780 nm). The device includes

four channels for four different optical power levels. The write channels (channels 2

to 4) can be controlled by fast LVDS (Low Voltage Differential Signaling).

The read channel generates a continuous output current, whereas channels 2 to 4 are

designed as write channels with very fast switching speed. All channels are summed

together and routed to one of the two outputs, IOUTA or IOUTB, controlled by the

select input, SELA. Each write channel (channel 2 to 4) can contribute up to 350 mA

to the total output current of up to 600 mA. The read channel can contribute up to

150 mA. Total gains of 100 (read channel) and 250 (channels 2, 3 and 4), are pro-

vided between each reference current input and the selected output. Although the

reference inputs are current inputs, voltage control is possible by using external resis-

tors. An on-chip RF oscillator is available to reduce laser-mode hopping noise during

read mode. The oscillator current amplitude can be set independently for the two

selectable outputs with two different resistors. Oscillation is enabled by a high signal

at the ENOSC pin. Complete shutdown of the output currents is achieved by a low sig-

nal at the ENABLE input.

In read mode, the reference currents (I2, I3, I4) should be switched off to reduce

power consumption.

In case of uncertain (balanced) enable signals, a built-in fail-safe circuit will reduce the

laser diode output current to a safe value.

4-Channel LVDS

Laser Driver for

Dual-layer

Application

ATR0849

Summary

Rev. 4851BS–DVD–06/05

Note: This is a summary document. A complete dorcument

is available under NDA. For more information, please con-

tact your local Atmel sales office.