4-Channel Laser Diode Driver + Oscillator Features General Description • 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 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 channels, with switching speeds of approximately one nanosecond rise/fall time. All four channels are summed together at the IOUT 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 IIN pin (virtually ground). The current seen at this pin is then amplified by 100X to become a current source at pin IOUT. Applications • • • • DVD drives CD-RW applications Writable optical drives Laser diode current switching Ordering Information Part No Temp. Range Package Outline # EL6257CU 0°C to +70°C QSOP-24 MDP0040 EL6257C - Product Brief EL6257C - Product Brief An on-chip 500 MHz oscillator 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 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 additional laser diode protection is provided since the OUTEN input will float high when open. Complete IOUT shut-off is also achieved by holding the ENABLE pin low, which will override the OUTEN control 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 IIN pin can be biased from a current DAC or other current source. Connection Diagram 1 24 2 23 3 22 4 21 5 20 6 19 7 18 8 17 9 16 10 15 11 14 12 13 GND VCC VCC IOUT IOUT GND RAMP ENABLE OSCEN VCC VCC GND 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. July 30, 1999 GND IINR GND IIN2 RFREQ IIN3 IIN4 OUTEN OUTEN2 OUTEN3 OUTEN4 GND EL6257C - Product Brief EL6257C - Product Brief 4-Channel Laser Diode Driver + Oscillator General Disclaimer Specifications contained in this data sheet are in effect as of the publication date shown. Elantec, Inc. reserves the right to make changes in the circuitry or specifications contained herein at any time without notice. Elantec, Inc. assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement. WARNING - Life Support Policy Elantec, Inc. products are not authorized for and should not be used within Life Support Systems without the specific written consent of Elantec, Inc. Life Support systems are equipment intended to support or sustain life and whose failure to perform when properly used in accordance with instructions provided can be reasonably expected to result in significant personal injury or death. Users contemplating application of Elantec, Inc. Products in Life Support Systems are requested to contact Elantec, Inc. factory headquarters to establish suitable terms & conditions for these applications. Elantec, Inc.’s warranty is limited to replacement of defective components and does not cover injury to persons or property or other consequential damages. July 30, 1999 Elantec Semiconductor, Inc. 675 Trade Zone Blvd. Milpitas, CA 95035 Telephone: (408) 945-1323 (888) ELANTEC Fax: (408) 945-9305 European Office: +44-118-977-6020 Japan Technical Center: +81-45-682-5820 2 Printed in U.S.A.