MAX3643 Maxim Integrated Products, MAX3643 Datasheet - Page 10

• Manufacturer Part Number: MAX3643
• Description: Burst Mode Laser Driver
• Manufacturer: Maxim Integrated Products

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An LVCMOS input, EN, is provided to disable both bias
and modulation currents under external control. The
maximum time to disable laser current with the EN con-
trol is 375ns.
A current limiter is provided to protect the laser diode
by shutting down both bias and modulation currents
when total current exceeds a value set by the resistor
connected from IMAX to ground. Do not use less than
3kΩ I
R
To program the laser modulation current using a cur-
rent DAC, connect VMSET to VREF, attach the DAC to
the MODSET pin and set the current according to:
Burst-Mode Laser Driver
Figure 2. Sample-and-Hold Timing Diagram
10
IMAX
______________________________________________________________________________________
MAX
graph in the Typical Operating Characteristics.
. See the I
1.2V
Programming the MODSET and
BIAS
Setting the Current Limit
+ I
MOD
Current Threshold vs.
3µs
BIASSET Inputs
Enable Input
INTERNAL MDIN VOLTAGE SAMPLER
BENOUT OUTPUT
≤ 125µs FOR BPON/GPON
BURST-ENABLE (BEN±) IN
100µs
MDOUT
To program the laser modulation current using a resis-
tor or digital potentiometer, connect VMSET to VREF,
attach a resistor from the MODSET pin to ground, and
set the current according to:
To program the laser modulation current using a PWM
voltage DAC (requiring a high-impedance load), attach
a DAC output to the VMSET pin, connect a resistor from
the MODSET pin to ground as shown in the Typical
Applications Circuit, and set the current according to:
I
I
MOD
MOD
I
MOD
=
=
R
R
MODSET
MODSET
= I
< 2.56mV
MODSET
V
1 2
DAC
.
V
+
+
R
R
MOD
MOD
x 88
× 88
×
88