19-2348; Rev 0; 2/02
MAX3865 Evaluation Kit
General Description
The MAX3865 evaluation kit (EV kit) has one circuit for
electrical evaluation and a second circuit for optical
evaluation. The electrical EV board is designed to famil-
iarize the user with the behavior of the automatic power
control (APC) and automatic modulation control (AMC)
features of the MAX3865 in an environment that is easy
to instrument using the many test points provided. The
optical EV board closely resembles what might be
found in an actual communications environment.
The electrical part of the EV kit is designed to familiar-
ize the user with the controlling action of the MAX3865.
The kit contains a synthetic laser plus monitor diode, for
which threshold current and gain can be varied through
jumper connections. The user can program values for
the bias (average) and modulation (peak-to-peak) cur-
rents in the monitor diode for a desired extinction ratio.
The synthetic laser can be changed to simulate varia-
tion of temperature or approaching end of life, and the
extinction ratio is held constant. Parameters such as
loop settling time or the restrictions imposed on the
maximum currents in the laser can also be observed.
o
Fully Assembled and Tested
o
Fully Matched for Best Return Loss
Features
Evaluates: MAX3865
Ordering Information
PART
MAX3865EVKIT
TEMP RANGE
-40°C to +85°C
IC PACKAGE
32 QFN
Electrical Component List
DESIGNATION
C11–C14, C20
C15–C18, C22,
C26
C19
C21
C23, C24
C25
C36–C39
D11, D13
D12
J3, J4, J5
QTY
5
6
1
1
2
1
0
2
1
3
DESCRIPTION
0.1µF
±10%,
10V ceramic
capacitors (0402)
0.01µF
±10%,
10V ceramic
capacitors (0402)
47pF
±5%,
10V ceramic capacitor
(0402)
22pF
±5%,
10V ceramic capacitor
(0402)
10µF
±10%,
10V tantalum
capacitors
0.01µF
±10%,
10V ceramic
capacitor (0603)
Do not install (0402)
Rectifier diodes, 1A
Digi-Key S1ADICT-ND
Red LED, T1 pkg
Digi-Key 363-ND
Test points
JU11–JU18
JU11–JU18
L12, L13
Q11
R9
R11, R12, R13
R14–R17
R18, R19
R20
R21
R22
R23
R24
8
8
2
1
1
3
4
2
1
1
1
1
1
J11–J15
5
DESIGNATION
QTY
DESCRIPTION
SMA connectors (edge mount,
round contact)
EFJohnson 142-0701-801
or Digi-Key J502-ND
Note:
Cut center pin to
approximately 1/16in length.
1-pin
✕
2-pin headers (0.1in
centers)
Shunts
1.2µH inductors
Coilcraft 1008 LS-122XKBC
PNP transistor
Central Semiconductor CMPT3906
100Ω
±1%
resistor (0402)
33kΩ
±5%
resistors (0603)
3.3kΩ
±5%
resistors (0603)
200Ω
±1%
resistors (0402)
20Ω
±5%
resistor (2010)
10Ω
±1%
resistor (1210)
33Ω
±1%
resistor (0603)
2kΩ
±1%
resistor (0603)
1.0kΩ
±1%
resistor (0603)
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
MAX3865 Evaluation Kit
Evaluates: MAX3865
Electrical Component List
(continued)
DESIGNATION
R25–R28
R29, R30
TP1, TP4,
TP12, TP13,
TP14, TP16,
TP17
QTY
4
2
DESCRIPTION
100kΩ variable resistors
Bourns 3296W
or Digi-Key 3296W-104-ND
10kΩ
±1%
resistors (0402)
DESIGNATION
JU51, JU52,
JU53, JU56
JU51, JU52,
JU53, JU56
L52
7
Test points
L53, L54
MAX3865 EGJ 32-pin QFN
Note:
U11 has an exposed
paddle that requires that it be
solder attached to the circuit
board to ensure proper
functionality of the part.
L55, L56, L57
L58
R2
R3, R4, R6, R7
R8, R62
R51, R52, R53
R54–R57
R58, R59
R60
R61
R65–R68
2
3
1
1
0
2
3
4
2
1
1
4
Optical Component List
(continued)
QTY
4
4
1
DESCRIPTION
1
×
2 pin headers, 0.1in centers
Shunts
1.2µH inductor
Coilcraft 1008CS-122XKBC
4µH inductors
BLM11A102S (0805)
2µH inductors
BLM11HA471SG (0603)
10µH inductor
Coilcraft DO1608C-103
10kΩ
±1%
resistor (0402)
Do not install (0402)
100Ω
±1%
resistors (0402)
33kΩ
±5%
resistors (0603)
3.3kΩ
±5%
resistors (0603)
200Ω
±1%
resistors (0402)
20Ω resistor (0402)
24.9Ω resistor (0402)
100kΩ variable resistors
Bourns 3296W or
Digi-Key 3296W-253-ND
MAX3865EGJ 32-pin QFN
Note:
U1 has an exposed paddle that
requires that it be solder attached to
the circuit board to ensure proper
functionality of the part.
Test points
U11
1
Optical Component List
DESIGNATION
C3
C4
C40–C43
C51–C54
C55–C58, C63
C59, C60
C61
D2
D51
D52
QTY
1
1
0
4
5
2
1
1
1
1
DESCRIPTION
10µF
±10%,
10V tantalum
capacitor
0.01µF
±10%,
10V ceramic
capacitor (0603)
Do not install (0402)
0.1µF
±10%,
10V ceramic
capacitors (0402)
0.01µF
±10%,
10V ceramic
capacitors (0402)
0.1µF
±10%,
10V ceramic
capacitors (0603)
1pF
±0.1pF,
10V ceramic
capacitor (0402)
User-supplied diode
Rectifier diode, 1A
Digi-Key S1ADICT-ND
Red LED, T1 pkg
Digi-Key P363-ND
SMA connectors, edge mount
(round contact)
EFJohnson 142-0701-801 or
Digi-Key J502-ND
Note:
Cut center pin to
approximately 1/16in length.
U51
1
VCC2, GND,
TP2, TP3, TP52,
TP53, TP54
None
None
None
7
1
1
1
MAX3865 EV kit circuit board, rev C
MAX3865 EV kit data sheet
MAX3865 data sheet
J51–J54
4
2
_______________________________________________________________________________________
MAX3865 Evaluation Kit
Component Suppliers
SUPPLIER
AVX
EFJohnson
Murata
PHONE
843-444-2863
402-474-4800
415-964-6321
FAX
843-626-3123
402-474-4858
415-964-8165
load when an actual laser is used.
3) Program the gain of the synthetic laser using the
jumper settings shown in Table 1. Remember that
the synthetic laser is not a real laser. It mimics only
some characteristics of a real laser. In particular, its
input behaves like a linear resistor and not like a
diode. As input current is increased, synthetic laser
voltage continues to increase rather than saturating
(at something in excess of 1V) like a real laser
(Figure 1).
4) AMC is the preferred operating mode for the
MAX3865. Average optical power output and
extinction ratio are automatically held constant.
Program the bias and modulation currents using the
AMC and APC set points.
Set the laser parameters from Table 1:
I
THRESHOLD
= 20mA
LASER Gain = 0.01
Program the AMC and APC set points:
• Program the AMC and APC
.
2V points:
1 set
I
APC
=
5
×
R27
+
2k
Ω +
3
.
3k
Ω
I
AMC
=
5
×
1
.
2V
R28
+
2k
Ω +
3
.
3k
Ω
Evaluates: MAX3865
Note:
Please indicate that you are using the MAX3865 when
contacting these component suppliers.
Quick Start
Electrical Evaluation
1) Data and clock Input levels—set the data rate at
20Mbps (10MHz) to allow measurement of the AC
current from the synthetic monitor diode with an
oscilloscope. If you are using relatively low-speed
data (up to about 100Mbps), it is acceptable to use
a single-ended input rather than fully differential.
Amplitude can be in the range:
a) Peak-to-peak differential voltage: 200mV to 1600mV
b) Instantaneous voltage at any input pin: 1.3V to (V
CC
+ 0.4V)
A convenient choice is 250mV peak-to-peak to
DATA+ with V
DR
connected to V
CC
at JU18.
Unless you are concerned about at-speed testing of
rise time or jitter, do not use the retiming feature of
the MAX3865 in the electrical EV kit.
2) Connector J15 must be connected to ground via
50Ω at all times. This can be a 50Ω resistor at the
connector, or a properly terminated 50Ω line to an
oscilloscope. Including the back-terminating resistor
R22, the peak-to-peak data voltage at J15 is:
V
P-P
(J15) = I
MOD
✕
20Ω
Note that this voltage is AC-coupled, with a time
constant of 8µs. The output from the MODN pin is
inverted because the MODQ pin is required for the
synthetic laser; MODN is terminated in a dummy
I
APC
=
250
µ
A for R27
=
18
.
7k
Ω
I
AMC
=
250
µ
A for R28
=
18
.
7k
Ω
Table 1. Synthetic Laser Gain Settings
GAIN SLOPE
(∆I
MD
/∆I
MODQ
)
Threshold Current
JU14
JU15
JU16 (MDX )
1
33
≈20mA
Open
Short
Short
1
100
≈20mA
Open
Open
Open or short
1
100
≈60mA
Short
Short
Open or short
1
300
≈60mA
Short
Open
Open
_______________________________________________________________________________________
3
MAX3865 Evaluation Kit
Evaluates: MAX3865
The resulting bias and modulation currents as seen
in Figure 1:
I
1
I
I
BIAS
=
I
THRESHOLD
+
APC
−
×
AMC
GAIN
2
GAIN
or
I
BIAS
=
32
.
5mA
I
I
MOD
=
AMC
or I
MOD
=
25mA
Gain
The bias and modulation currents can be verified
by using a voltmeter to measure V
BIASMON
from
TP14 to TP12 and V
MODMON
from TP14 to TP13:
I
BIAS
=
48
×
V
BIASMON
200
32
×
V
MODMON
200
5) Set V
CC
= 3.3V. Remember that the operating volt-
ages at the MAX3865 output pins must at all times
satisfy the minimum voltages for compliance:
V
BIAS
or V
BIASX
≥
1.0V
V
MODQ
or V
MODN
≥
1.8V
V
BIAS
= V
CC_LASER
- (I
BIAS
+ I
MOD
)
✕
10Ω, if JU14 is short
V
BIAS
= V
CC_LASER
- (I
BIAS
+ I
MOD
)
✕
30Ω, if JU14 is open
Min V
MODN
= V
CC_LASER
- I
MOD
✕
30Ω
The operating voltages must also satisfy the maxi-
mum voltages for compliance:
V
BIAS
or V
BIAS
_X
≤
(chip V
CC
+ 0.4V)
V
MODQ
or V
MODN
≤
(chip V
CC
+ 1.2V)
To satisfy these constraints, the V
CC_LASER
for the
synthetic laser must be disconnected from the main
supply to the chip (at JU17), and connected to
some higher voltage. For the currents programmed
in step 4, set V
CC_LASER
= 4.5V.
6) The synthetic laser current can be observed by the
voltage difference between JU14 and TP17. The
total current flows in 10Ω resistor R21, but note that
its bandwidth is restricted to about 100MHz by the
combination of C19 and the input capacitance of
the test oscilloscope. Similarly, the current in the
I
MOD
=
The corresponding monitor currents: I
BIASMON
≈
677µA and I
MODMON
≈
781µA. See Figure 1 to see
how the set-point currents and actual bias and
modulation currents are related.
Table 2. Test Setup Summary for the AMC Mode with the Electrical EV Kit
COMPONENT
J11 (DATA-)
J12 (DATA+)
J13 (CLK+)
J14 (CLK-)
JU11
JU12
JU13
JU14
JU15
JU16
JU17
JU18
R25
R26
R27
R28
STATE
Unconnected
Data in
Unconnected
Unconnected
Short circuit
Open circuit
Open circuit
Open circuit
Open circuit
Open circuit
Open circuit
Short circuit
Fully clockwise
Fully clockwise
Approximately 20kΩ
Approximately 20kΩ
—
250mV
P-P
at 20Mbps (10MHz)
—
—
Disable data latch
Enable AMC mode
Enable AMC mode
Set laser gain and threshold
Set laser gain and threshold
Disconnect monitor-diode shunt
Use V
CC_LASER
≈
(VCC + 1)
Set data reference VDR = VCC
Set laser i
BIASMAX
= 100mA
Set laser i
MODMAX
= 60mA
Set monitor-diode i
APC
≈
250µA
Set monitor-diode i
AMC
≈
250µA
COMMENT
4
_______________________________________________________________________________________
MAX3865 Evaluation Kit
Evaluates: MAX3865
(a) DC-COUPLED ELECTRICAL EV KIT
PEAK-TO-PEAK CALLED I
AMC
MD
CURRENT
GAIN
AVERAGE CALLED I
APC
LASER
CURRENT
I
MOD
THRESHOLD
(b) AC-COUPLED OPTICAL EV KIT
PEAK-TO-PEAK CALLED I
AMC
MD
CURRENT
I
BIAS
AVERAGE CALLED I
APC
I
BIAS
I
MOD
LASER
CURRENT
Figure 1. Relation Between Chip-Output Currents and Monitor-Diode Currents
_______________________________________________________________________________________
5
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