Datasheet

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R
BIASMAX
+
343 V
40 mA
+ 8.6 kW
(21)
SELECT V
MONB
AND V
MONP
RANGE
V
MONB
[V] +
R
MONB
[W] I
BIAS
[A]
68
+
768 W I
BIAS
[A]
68
+ 11.29 W I
BIAS
[A]
(22)
V
MONP
[V] + R
MONP
[W] I
PD
[A] + 200 W I
PD
[A]
(23)
LASER DIODE INTERFACE
ONET4211LD
SLLS688A NOVEMBER 2005 REVISED SEPTEMBER 2007
Monitoring the bias current is achieved by taking the fractional (1/68) bias current and developing a voltage
across an external resistor to ground. Equation 22 provides the value for V
MONB
for a resistor value equal to
768 .
Monitoring of the photo current is achieved by taking a mirror of I
PD
and developing a voltage across an external
resistor to ground. Equation 23 provides the value for V
MONP
for a resistor equal to 200 .
The output stage of the ONET4211LD is optimized for driving a 20- load. The combination of a damping
resistor, R
D
, along with the resistance of the laser diode, must be 20 for impedance matching. The suggested
typical value for R
D
is 6 to 15 . A bypass capacitor of 10 nF placed close to the laser anode also helps to
optimize performance.
20 Submit Documentation Feedback Copyright © 2005 2007, Texas Instruments Incorporated
Product Folder Link(s): ONET4211LD