Datasheet

Laser Driver for Projectors
MAX3600
14
Control Logic
The control logic provides video selection, laser enable,
and power savings.
Video Selection
The video demultiplexer creates signals VIDEO1,
VIDEO2, and VIDEO3. The VSEL[1/3/4] bits can be used
to select the input video for OUTPUT1, OUTPUT3, and
OUTPUT4.
Laser Control
When EN_MAIN is low, all driver outputs are off. This
signal works asynchronously (no clock is required to
disable outputs).
The video marker (VM) input can be used to disable
selected outputs when a video signal is not present
(Figure 11). The VM_EN[1:4] bit settings determine
which outputs respond to the VM signal.
Propagation delay from VM↑ or EN_MAIN↑ to output
active is typically 35ns + 2/f
PIXEL
.
Periodic Off Generator
The periodic off (PO) generator quickly switches off
OUTPUT2. The PO event is placed within a pixel if PO is
set high during a pixel as shown in Figure 12.
The PO event location within the pixel is programmed
from the serial port. Each pixel is divided into “m” equal
time subpixels as shown in Figure 13. The PO_M setting
determines the number of subpixels, where:
m = (PO_M +1) x 8
The PO start and PO stop locations (in subpixels) are
defined by the P1, P1S, P2, and P2S bits.
Start Subpixel =
[(P1 + 1) MOD (PO_M + 1)] x 8 + P1S + 1
Stop Subpixel =
[(P2 + 1) MOD (PO_M + 1)] x 8 + P2S + 1
The start and stop locations should be selected to
ensure that the PO event occurs > one rise/fall time from
the pixel update. The minimum off-time is four subpixels.
Select P1, P2 P PO_M.
The PO oscillator frequency (f
PO
) = f
PIXEL
x (PO_M + 1).
The intended operating range for f
PO
is 133MHz to
200MHz.
Figure 11. Video Marker Figure 12. Periodic Off (PO) Example
VIDEO AREA
VM = 1
NONVIDEO AREA (VM = 0)
SELECTED OUTPUTS DISABLED
HORIZONTAL SCAN
VERTICAL SCAN
OUT2 (GREEN LASER CURRENT)
PO EVENT
TIME
1 1 00
PO
PIXEL 1 PIXEL 2 PIXEL 3 PIXEL 4