LMH6525 Datasheet, PDF (1/15 Pages) National Semiconductor (TI) – Four-hannel Laser Diode Driver with Dual Output

June 2005
LMH6525/LMH6526
Four–Channel Laser Diode Driver with Dual Output
General Description
The LMH™6525/6526 is a laser diode driver for use in
combination DVD/CD recordable and rewritable systems.
The part contains two high-current outputs for reading and
writing the DVD (650 nm) and CD (780 nm) lasers. Func-
tionality includes read, write and erase through four separate
switched current channels. The channel currents are
summed together at the selected output to generate multi-
level waveforms for reading, writing and erasing of optical
discs. The LVDS interface delivers DVD write speeds of 16x
and higher while minimizing noise and crosstalk. The
LMH6525/6526 is optimized for both speed and power con-
sumption to meet the demands of next generation systems.
The part features a 150 mA read channel plus one 300 mA
and two 150 mA write channels, which can be summed to
allow a total output current of 600 mA or greater. The chan-
nel currents are set through four independent current inputs.
An on-board High-Frequency Modulator (HFM) oscillator
helps reduce low-frequency noise of the laser and is enabled
by applying LVDS levels on the ENOSC pins for the
LMH6525, while the LMH6526 is enabled by applying an
asymmetrical signal on the ENOSC pin. The fully differential
oscillator circuit minimizes supply line noise, easing FCC
approval of the overall system. The SELA/B pin (active
HIGH) selects the output channel and oscillator settings.
External resistors determine oscillator frequency and ampli-
tude for each setting. The write and erase channels can be
switched on and off through dedicated LVDS interface pins.
Features
n Fast switching: Rise and fall times: 0.6/1.0 ns.
n Low Voltage Differential Signaling (LVDS) channels
enable interface for the fast switching lines
n Low output current noise: 0.24 nA/
n Dual Output: Selectable by SELA/B pin (active HIGH)
SELA = LMH6526 SELB = LMH6525
n Four independent current channels
Gain of 300, 300 mA write channel
Gain of 150, 150 mA low-noise read channel
Two gain of 150, 150 mA write channels
600 mA minimum combined output current
n Integrated AC Coupled HFM Oscillator
Selectable frequency and amplitude setting
by external resistors
200 MHz to 600 MHz frequency range
Amplitude to 100 mA peak-to-peak modulation
n Complete shutdown by ENABLE pin
n 5V single-supply operation
n Logic inputs TTL and CMOS compatible
n Space saving Leadless Leadframe Package (LLP^®-28)
n LMH6525 has differential enable oscillator inputs
n LMH6526 has single ended enable oscillator inputs
Applications
n Combination DVD/CD recordable and rewritable drives
n DVD camcorders
n DVD recorders
Block Diagrams
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LLP^® is a registered trademark of National Semiconductor.
LMH™ is a trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation DS201101
20110109
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