Evaluates: MAX3669ETG
MAX3669ETG Evaluation Kit
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Quick Start
Electrical Setup (Default)
In the electrical configuration, an APC test circuit is
included to emulate a semiconductor laser with a moni-
tor photodiode. Monitor diode current is provided by Q1,
which is controlled by an operational amplifier (U3). The
APC test circuit, consisting of U3 and Q1, applies the
simulated monitor diode current to the MAX3669ETG’s
MD pin. The ratio of I
BIAS
/ I
MD
is R24 / R23 = 100. To
ensure proper operation in the electrical configuration,
set up the evaluation board as follows:
1) Verify inductor L2 is not installed.
2) Remove the shunt from P1 to enable the output.
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.
3) Adjust R14, the MOD (R
MODSET
) potentiometer, for
10kΩ resistance between pins 2 and 3 (test point 5
and ground).
4) Adjust R15, the BIAS (R
BIASMAX
) potentiometer, for
10kΩ resistance between pins 2 and 3 (test point 4
and ground).
5) Adjust R16, the APC (R
APCSET
) potentiometer, for
10kΩ resistance between pins 2 and 3 (test point 6
and ground).
6) Power up the board with a +3.3V supply.
7) Apply a differential input signal (max amplitude
≤800mV per side) to J1 and J2 (DATA+ and DATA-).
8) Attach a high-speed oscilloscope with 50Ω inputs
to J3.
9) Adjust R
BIASMAX
(R15) and R
APCSET
(R16) until the
desired laser-bias current is achieved (refer to the
note in the Applications Information section of the
MAX3669 data sheet).
10) Adjust R
MODSET
(R14) until the desired laser-modu-
lation current is achieved.
Note: See the Adjustment and Control Descriptions table.
Optical Setup
For optical operation, the electrical APC test circuit
must be disabled. For optical evaluation of the
MAX3669ETG, configure the EV kit as described in
Component Modifications for Optical Configuration:
1) Remove the shunt from P1 to enable the output.
2) Connect a TO-style header laser and monitor diode
(Figure 1) as follows:
• Keeping the leads to the laser diode as short as
possible, connect the laser diode on the compo-
nent side of the board between R20 and V
CC
with the cathode connected to R20 and the
anode connected to V
CC
.
• Connect the monitor diode on the underside of the
the board with the anode connected to the
MAX3669ETG’s MD pin and the cathode con-
nected to V
CC
.
Note: When performing resistance checks, manually
set the ohmmeter to a high range to avoid forward bias-
ing the on-chip ESD protection diodes.
3) Adjust R14, the MOD (R
MODSET
) potentiometer, for
maximum resistance between pins 2 and 3 (test
point 5 and ground).
4) Adjust R15, the BIAS (R
BIASMAX
) potentiometer, for
maximum resistance between pins 2 and 3 (test
point 4 and ground).
5) Adjust R16, the APC (R
APCSET
) potentiometer, for
desired optical power. (Refer to the Design
Procedure section of the MAX3669 data sheet.)
6) Power up the board with a +3.3V supply.
7) Apply a differential input signal (≤800mV per side)
to J1 and J2 (DATA+ and DATA-).
8) Attach the laser-diode output to an optical/electrical
converter.
Component Modifications
for Optical Configuration
