Evaluates: MAX3863
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MAX3863 Evaluation Kit
Quick Start
The MAX3863 EV kit contains two circuits, one for elec-
trical evaluation and one for optical evaluation. The
optical circuit has solder pads suitable for mounting a
laser diode module with a built-in monitor diode. The
electrical circuit has a connector for a 50Ω oscilloscope
hookup. In the electrical circuit, the monitor diode feed-
back is simulated by a current-controlled current
source formed by U3 and Q2.
Electrical Evaluation
1) If the data is latched, place the shunt for JU10 to
ground RTEN to enable the clock input. Otherwise,
set JU10 so that RTEN is connected to VCC.
2) Set the shunt JU9 to ground the EN input so that the
MAX3863 is enabled.
3) Remove JU16 to enable the APC loop. The bias
current is controlled by R43 and the gain of the APC
test circuit. See Figure 2.
4) Remove JU4 to disable modulation compensation.
Note: When performing the following resistance
checks, manually set the ohmmeter to a high range
to avoid forward biasing the on-chip ESD protection
diodes.
5) Adjust R13, the MODSET potentiometer, for 5.9kΩ
between TP3 and ground. This sets the modulation
current to approximately 40mA. Refer to the
MAX3863 data sheet to program other values of
I
MOD
.
6) Adjust R12, the BIASMAX potentiometer, for 2kΩ
between TP2 and ground. This allows the APC loop
to control I
BIAS
up to 100mA.
7) Adjust R43, the APCSET potentiometer, for 4.7kΩ
between TP10 and ground. This sets I
MD
to
1.25mA. Given the APC test circuit gain of
0.025mA/mA, the required bias current is approxi-
mately 50mA.
8) Apply a differential input signal of 250mV
P-P
to the
DATA inputs, and to the CLK inputs if retiming is
enabled.
9) Attach a high-speed oscilloscope with 50Ω inputs
to J9.
10) The bias current can be measured by:
11) Power up the board with a +3.3V supply.
12) Add modulation compensation by installing JU4.
Connect R34 to the MODCOMP pin to increase the
modulation current by 0.5 times the bias current.
