EL6257C - Product Brief
EL6257C - Product Brief
4-Channel Laser Diode Driver + Oscillator
Features
• High-performance laser diode
driver
• Voltage-controlled output current
source to 150 mA per channel,
requiring one external set resistor
per channel
• Current-controlled output current
source to 150 mA per channel
• Rise time = 1.0 ns
• Fall time = 1.1 ns
• On chip oscillator with frequency
and amplitude control by use of
external resistors to ground
• Oscillator to 500 MHz
• Oscillator to 100 mA pk/pk
• Single +5V supply (±10%)
• Current amplification = 100
• Disable feature for power-up
protection and power savings
• TTL/CMOS control signals
General Description
The EL6257C is a high-performance four channel laser diode current
amplifier that provides controlled current to a grounded laser diode.
The four amplifiers can provide up to 150 mA per channel of DC or
pulsed current. Channels 2, 3, and 4 must be used as the write chan-
nels, with switching speeds of approximately one nanosecond rise/fall
time. All four channels are summed together at the I
OUT
output, allow-
ing 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 by 100X to become a current source at pin I
OUT
.
An on-chip 500 MHz oscillator is provided to allow current modula-
tion 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 in this data sheet for further
explanation). The oscillator will also turn off whenever any of the
OUTEN pins for channels 2, 3, and 4 (the write channels) are low (see
truth table).
Output current pulses are enabled when an ‘L’ signal is applied to the
OUTEN pin. No output current flows when OUTEN is ‘H’, and addi-
tional 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 con-
trol pins.
The external resistors 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.
Applications
•
•
•
•
DVD drives
CD-RW applications
Writable optical drives
Laser diode current switching
Ordering Information
Part No
EL6257CU
Temp. Range
0°C to +70°C
Package
QSOP-24
Outline #
MDP0040
Connection Diagram
GND
I
INR
GND
I
IN2
RFREQ
I
IN3
I
IN4
OUTEN
OUTEN2
OUTEN3
OUTEN4
GND
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
GND
V
CC
V
CC
I
OUT
I
OUT
GND
RAMP
ENABLE
OSCEN
V
CC
V
CC
GND
July 30, 1999
Note:
All information contained in this data sheet has been carefully checked and is believed to be accurate as of the date of publication; however, this data sheet cannot be a “controlled document”. Current revisions, if any, to these
specifications are maintained at the factory and are available upon your request. We recommend checking the revision level before finalization of your design documentation.
© 2001 Elantec Semiconductor, Inc.
ELANTEC [ ELANTEC SEMICONDUCTOR ]
