AD9660KR-REEL Ver la hoja de datos (PDF) - Analog Devices
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AD9660KR-REEL Datasheet PDF : 12 Pages
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Typical Performance Characteristics–AD9660
6.25mV
20mV
2ns
–193.8mV
ML64116R
OUTPUT
TEK 11802
50Ω
O'SCOPE
AD9660
50Ω
–120V
ANTEL
ARS1
PHOTO DETECTOR
Figure 1. Driving ML64116R Laser @ 30 mW
35
30
25
20
15
10
5
0
0
5
10
15
20
25
ROFFSET – kΩ
Figure 2. IOFFSET vs. ROFFSET
THEORY OF OPERATION
The AD9660 combines a very fast output current switch with
onboard analog light power control loops to provide the user
with a complete laser diode driver solution. The block diagram
illustrates the key internal functions. The control loops of the
AD9660, the bias loop and the write loop, adjust the output
current level, IOUT, so that the photo diode feedback current,
IMONITOR, out of SENSE IN is proportional to the analog input
voltage at BIAS LEVEL or WRITE LEVEL. Since the monitor
current is proportional to the laser diode light power, the loops
effectively control laser power to a level proportional to the ana-
log inputs. The control loops should be periodically calibrated
independently (see Choosing CBIAS HOLD and CWRITE HOLD).
The offset current generator produces an open loop output cur-
rent, IOFFSET. Its level is controlled by an external set resistor or
a current out DAC (see Figure 2). While IOFFSET is not cali-
brated as the currents from the bias and write loops are, it can
be very versatile (see Offset Current below).
WRITE HOLD
TTL
DISABLE
TTL
WRITE PULSE
TTL
WRITE CAL
WRITE LEVEL
ANALOG
CGAIN
GAIN
50
RGAIN
POWER
MONITOR
ANALOG
BIAS LEVEL
ANALOG
TTL
BIAS CAL
BIAS HOLD
TTL
OFFSET PULSE
DISABLE
CIRCUIT
AD9660
VOLT
REF
VREFOUT
*
DELAY
5pF V:1
VREF
IMODULATION
1:10
IOUT
OUTPUT
2* IMONITOR
TZA
VREF
1.85:1
4.0V SENSE IN
IMONITOR
VREF
V:1
5pF
IBIAS
1:10
WRITE LOOP
LASER
DIODE
PHOTO
DETECTOR
BIAS LOOP
1:10
IOFFSET
1.4V
Figure 3. Functional Block Diagram
OFFSET CURRENT
SET
+VS
* 10ns DELAY ON RISING
EDGE; 0ns ON FALLING
REV. 0
–5–
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