MAX3948 Evaluation Kit
Evaluates: MAX3948
General Description
The MAX3948 evaluation kit (EV kit) is a fully tested and
assembled demonstration board that provides opti-
cal evaluation of the MAX3948 DC-coupled, 1Gbps to
11.3Gbps laser driver. The controlling software commu-
nicates with the EV kit through the USB port and provides
simplified control of all functions of the MAX3948. The
EV kit can be fully powered by the USB port, or the user
can choose to power the MAX3948 by a single external
3.3V supply while the USB port supplies the on-board
microcontroller. The flex-cable connection on the evalu-
ation board allows attachment of lasers incorporating
flex-cables.
DESIGNATION
C1, C3, C4,
C5, C8, C16
C2
C6, C9
C7, C12, C29
C11, C13, C15
C21, C22
C25, C26, C27,
C49, C52
C28
C33
C34, C55
C35, C37, C38
D6
J1, J2
J3, J4,
TP1–TP4,
TP6–TP15
J5, J6, J7, J9,
J10
J8
L1
1
2
3
1
2
16
QTY
6
1
0
3
3
2
5
DESCRIPTION
0.01FF
Q10%
ceramic capacitors
(0402)
0.3pF
Q0.1pF
ceramic capacitor
(0201)
0.5pF
Q0.1pF
ceramic capacitors
(0402)
0.1FF
Q20%
ceramic capacitors
(0204)
10FF
Q10%
ceramic capacitors
(0805)
33pF
Q10%
ceramic capacitors
(0402)
0.1FF
Q10%
ceramic
capacitors (0402)
Not installed (0201)
0.01FF
Q10%
ceramic capacitor
(0201)
1FF
Q10%
ceramic
capacitors (0603)
4.7FF
Q10%
ceramic
capacitors (0805)
Green LED
SMA connectors, edge mount
Test points
U6
U10
Y2
5
1
1
1 x 2 headers, 0.1in centers
Mini-B USB connector
22FF,
Q20%
inductor
Taiyo Yuden CBC3225T220M
None
1
0
1
1
Features
S
Drives Differentially-Connected Lasers
S
Software Control of the MAX3948
S
Power Supplied Through USB or External
Connection
EV Kit Contents
S
MAX3948 EV Kit Board
Ordering Information appears at end of data sheet.
Component List
DESIGNATION
L2, L3
L4
L10, L14
R1
R3
R4, R31,
R51, R53
R5, R6
R7
R12
R15, R50
R18, R52, R55,
R66, R73
R24
SW1
U1
QTY
2
1
2
1
1
4
2
1
0
2
5
1
1
1
DESCRIPTION
18nH
Q2%
inductors (0402)
Ferrite bead (0402)
Murata BLM15GG471
10FH
Q10%
inductors (0603)
1.00kI
Q1%
resistor (0402)
680I
Q5%
resistor (0402)
10kI
Q5%
resistors (0402)
20I
Q5%
resistors (0402)
100I
Q5%
resistor (0201)
Not installed (0201)
4.7kI
Q5%
resistors (0402)
51I
Q5%
resistors (0402)
1.5kI
Q5%
resistor (0402)
SPDT switch
1Gbps to 11.3Gbps , SFP+ laser
driver (16 TQFN)
Maxim MAX3948ETE+
Low-noise LDO regulator (8
TDFN)
Maxim MAX8902AATA+
User-supplied TOSA
Microcontroller (28 SO)
Microchip PIC16C745-I/SO
6MHz crystal
ECS Inc. ECS-60-32-5PXDN
MAX3948 EVALUATION BOARD,
REV A
U2
1
For pricing, delivery, and ordering information, please contact Maxim Direct at
1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
19-6081; Rev 0; 10/11
MAX3948 Evaluation Kit
Evaluates: MAX3948
Quick Start
Note:
In the following sections, software-related items are
identified by bolding. Text in
bold
refers to items directly
from the EV kit software. Text in
bold and underlined
refers to items from the Windows
®
operating system.
1)
2)
3)
Solder a laser to U6. See
Figure 1
for more informa-
tion about the laser connection.
Set SW1 to the desired power-supply option (USB or
external supply).
If an external power supply is used, set the voltage
to 3.3V, the current limit to 300mA, and connect the
supply to the board.
4)
Get the latest version of the EV kit software
(MAX3948Rev1.ZIP) by contacting Maxim customer
support at
www.maximintegrated.com/support.
After receiving the file unzip it to a local folder
and run the installation executable (setup.EXE).
Installation requires administrative rights and can
also require Internet access to download the nec-
essary drivers.
After installation is complete, follow this path to
start the program:
Start
→
All Programs
→
Maxim
Integrated Products
→
MAX3948 EV Kit GUI.
Connect the computer to the EV kit with a USB cable
(A-male to Mini-B-Male). LED D6 should illuminate,
indicating that USB power is detected. Click the
USB
Connect
button in the software to initiate communi-
cation to the EV kit. The
Status
indicator turns green
when communication is established.
Connect a 50I source to TIN- and TIN+ (J1 and J2).
Set the source differential amplitude to 500mV
P-P
.
Connect the output from the TOSA to an optical
receiver (optical-to-electrical converter or optical
input head on an oscilloscope).
All device controls are available in the software. Fault
and warning indicators are displayed on the right side
of the GUI window. When a hard fault has occurred,
the part goes into latched shutdown. The source of
the fault should be removed and the
DISABLE
check-
box should be toggled to reset the part.
5)
6)
7)
1
8)
U6
9)
GND
LD ANODE
LD CATHODE
GND
N.C.
N.C.
Figure 1. TOSA Connection
10) The registers contain a default setting and can be
read using the
Tx Read All
button. For detailed reg-
ister functions, refer to the MAX3948 IC data sheet.
Figure 2. MAX3948 EV Kit Software
Windows is a registered trademark of Microsoft Corp.
Maxim Integrated
2
MAX3948 Evaluation Kit
Evaluates: MAX3948
11) To enable the part, the
DISABLE
checkbox should
be toggled (check, then uncheck) and the
TX
Enable
checkbox should be checked. After doing
this, click the
TX Read All
button twice and check to
see if any faults are indicated. If everything is set up
properly all fault indicators should be green.
12) The
Tx De-emphasis Control
can be used to adjust
the eye diagram. After choosing a new setting,
click the
Tx De-emphasis Control Load
button fol-
lowed by the
IMOD Load
button. Doing so loads the
new pre-emphasis setting to the modulation current
driver. Further improvements to the eye diagram can
be accomplished by tuning the component values of
C2, C6, C9, C28, L2, L3, R5, R6, R7, and R12.
Along the right-hand side of the GUI are fault indicators
that show the status of the TXSTAT1 and TXSTAT2 regis-
ters. Hard faults disable the part and require a toggling
of the
DISABLE
checkbox to restart the part (once the
source of the fault has been removed). The hard faults
can be masked by checking the appropriate box beside
the fault indicator. Soft faults operate as warnings but
do not disable the part. Automatic updating of the fault
monitors can be enabled by checking the
Auto Read
Monitors
checkbox.
Fault Indicators
Output Network
The output network has multiple components to improve
the optical eye diagram. The RC shunts on the laser’s
anode and cathode (R5, C6, R6, and C9) affect the
S22 of the MAX3948 and must be placed very close to
the output pins TOUTA and TOUTC. The differential RC
(R7 and C2) also affects the S22 and must be placed
as close as possible to the output. Another differential
RC (R12 and C28) is placed as close as possible to the
laser connector to help compensate for the mismatch in
impedance where the TOSA solders to the PCB. These
last two components may not be necessary depending
on the TOSA.
Graphical User Interface (GUI)
The GUI consists of three main blocks: DC and modula-
tion control, data path adjustments, and fault indicators.
For DC and modulation current there are three controls:
set current, set maximum, and increment. The left-side
data-entry boxes allow the user to write to the SET_IDC
or SET_IMOD register directly, as long as that value is
below the value loaded in the IDCMAX and IMODMAX
registers. The middle data-entry boxes allow the user
to write to the IDCMAX and IMODMAX registers. The
right-side data-entry boxes allow the user to increment
or decrement the bias and modulation current registers
over a
Q15
LSB range by writing to the DCINC and
MODINC registers. The appropriate
Load
button must be
clicked to initiate a register write. The
Read
buttons read
and display the values held in the SET_IDC/SET_IMOD,
IDCMAX/IMODMAX, and DCINC/MODINC registers.
This block allows control of de-emphasis, the input
equalization, and data polarity. The
Tx De-emphasis
Control
has a drop-down box with four options for setting
the TXDE_MD register. When manual control is selected,
the
De-emphasis
checkbox becomes available to write
values to the SET_TXDE register. The
Tx EQ Control
data-entry boxes let you set the two SET_TXEQ bits,
checked for a “1” and unchecked for a “0”. When the
Tx
Polarity
box is checked, the TOUT+ pin sinks current
when TIN+ is high (typical setup). The output polarity is
inverted if the box is unchecked.
DC and Modulation Control
Data Path Adjustments
Maxim Integrated
3
TIN-
6
RB2
RB1
RB0
VDD
VSS
D6
FAULT
4
TP4
BMON
R1
1.00kΩ
V
CC
J8
1
VBUS
D-
D+
NC
GND
L2
18nH
2
R24
1.5kΩ
3
4
5
C12
0.1µF
L14
10µH
R5
20Ω
C29
0.1µF
C6
0.5pF
RC7
RC6
D+
D-
15
16
17
C34
1µF
R3
680Ω
18
19
C35
4.7µF
C27
0.1µF
C49
0.1µF
C37
4.7µF
TP3
TX_FAULT
3
20
TX_FAULT
BMON
21
VUSB
VSEL
L1
22µH
C38
4.7µF
R73
51Ω
2
22
FAULT
R4
10kΩ
J10
1
TX_DISABLE
U1
23
DISABLE
RA4
R66
51Ω
J9
TP2
VSEL
TIN+
R31
10kΩ
VCC
VCC
VCCT
TOUTA
TOUTC
13
RC2
14
5
6
7
8
VCCT
Z =25Ω
0
J4
3.3V
J3
GND
TP15
C16
0.01µF
C15
10µF
VCCD
L4
BLM15GG471
VCC
R12
C28
OPEN OPEN
VUSB
SW1
U2
OUT
BYP
OUTS
SELB
5
6
7
C8
0.01µF
C13
10µF
8
TP9
TP14
5V
1
TP10 TP11 TP12 TP13
U6
2
3
4
5
CASE
IN
LD_CATHODE
3
EN
4
SELA
PD_CATHODE
C11
10µF
MAX8902
LD_ANODE
2
GND
CASE
1
NC
Z
0
=25Ω
Maxim Integrated
VCCD
C55
1µF
R51
10kΩ
R53
10kΩ
CSEL
V
CC
V
CC
C4
0.01µF
C5
0.01µF
SCL
SDA
TP1
DISABLE
16
DISABLE
15
14
13
C1
0.01µF
R15
4.7kΩ
J1
TIN-
J2
TIN+
R50
4.7kΩ
C52
0.1µF
U10
RB7
RB6
RB5
RB4
RB3
24
25
R52
51Ω
26
51Ω
J5
27
R55
J6
28
J7
R18
51Ω
C3
0.01µF
TP6
SCL
TP7
SDA
TP8
CSEL
SCL
SDA
12
11
SCL
SDA
VUSB
1
MCLR
2
RA0
Figure 3. MAX3948 EV Kit Schematic
MAX3948
CSEL
CSEL
VOUT
10
9
C33
0.01µF
V
CC
C7
0.1µF
R7
C2
100Ω 0.3pF
C9
0.5pF
R6
20Ω
L10
10µH
L3
18nH
6
3
RA1
VUSB
4
RA2
5
RA3
7
RA5
8
VSS
9
OSC1
10
OSC2
C21
33pF
Y2
C22 11 RC0
33pF
12
RC1
VUSB
C26
0.1µF
C25
0.1µF
MAX3948 Evaluation Kit
Evaluates: MAX3948
4
MAX3948 Evaluation Kit
Evaluates: MAX3948
Figure 4. MAX3948 EV Kit Component Placement Guide—
Component Side
Figure 6. MAX3948 EV Kit PCB Layout—Ground Plane
Figure 5. MAX3948 EV Kit PCB Layout—Top Side
Figure 7. MAX3948 EV Kit PCB Layout—Power Plane
Maxim Integrated
5
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