MAX3740AEVKIT Maxim Integrated Products

19-2694; Rev B, 07/04
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The MAX3740A evaluation kit (EV kit) is an assembled
demonstration board that provides complete optical and
electrical evaluation of the MAX3740A VCSEL driver.
I
The output of the evaluation kit can be interfaced to an
SMA connector, which can be connected to a 50 terminated oscilloscope. With slight modifications, the
evaluation kit can also be used to evaluate the
MAX3740A operation with a common-cathode VCSEL.
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DESIGNATION QTY
DESCRIPTION
C1, C2, C5, C9,
0.1µF ±10% ceramic capacitors
8
C13, C15, C16,
(0402)
C17
♦
Fully Assembled and Tested
♦
Single +3.3V Power Supply Operation
♦
Allows Optical and Electrical Evaluation
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PART
TEMP. RANGE
IC PACKAGE
MAX3740AEVKIT -40°C to +85°C
24 QFN
DESIGNATION QTY
DESCRIPTION
R16
1 500kΩ potentiometer
Q1, Q2
2
NPN transistors (SOT23)
Q3
1
MOSFET (SOT23)
JU1–JU8, JU10
9
2-pin headers, 0.1in centers
J1–J7
7
SMA connectors, round contacts
1
0.047µF ±10% ceramic capacitor
(0402)
C4, C6, C7, C8,
C11, C12
6
0.01µF ±10% ceramic capacitors
(0402)
C10
1
Open
C14
1
10µF ±10% ceramic capacitor
(0805)
U1
1
MAX3740AETG (24QFN)
U2
1
MAX495ESA (8 SO)
C18
1
10µF ±10% tantalum capacitor
(B Case)
None
9
Shunts
D1
1
VCSEL laser and photodiode*
None
1
MAX3740A EV board
D2
1
LED, red T1 package
None
1
MAX3740A data sheet
L1, L2, L3
3
L4
1
1µH inductor (1008CS)
R1, R2
2
10kΩ potentiometers
R3
1
350Ω ±1% resistor (0402)
R4
1
2.49kΩ ±1% resistor (0402)
R5, R12
2
499Ω ±1% resistors (0402)
R6, R13
2
10kΩ ±5% resistors (0402)
R7
1
0Ω ±1% resistor (0402)*
R8
1
4.7kΩ ±1% resistor (0402)
R9, R11
2
49.9Ω ±1% resistors (0402)
R10, R26, R27,
R34, R35, R36
6
Open
R14
1
20kΩ potentiometer
R15
1
50kΩ potentiometer
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TP1–TP11, TP20,
13 Test points
TP21
* These components are not supplied but can be
populated for VCSEL testing.
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SUPPLIER
PHONE
FAX
AVX
843-444-2863
843-626-3123
Coilcraft
847-639-6400
847-639-1469
Digi-Key
218-681-6674
218-681-3380
EF Johnson
402-474-4800
402-474-4858
Murata
415-964-6321
415-964-8165
Note: Please indicate that you are using the MAX3701
when ordering from these suppliers.
_________________________________________________________________Maxim Integrated Products
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.
1
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MD
In the electrical configuration, an automatic power control
(APC) test circuit is included to emulate a semiconductor
laser with a monitor photodiode. Monitor diode current is
provided by transistor Q1, which is controlled by an
operational amplifier (U2). The APC test circuit,
consisting of U2 and Q1, applies the simulated monitor
diode current to the MD pin of the MAX3740. To ensure
proper operation in the electrical configuration, set up the
evaluation board as follows:
1)
2)
3)
I
BIAS
=
V
2× R
PWRMON
PWRSET
9× V
350Ω
BIASMON
Note: If the voltage at TP1 exceeds VPMTH (0.8V typ)
or TP3 exceeds VBMTH (0.8V typ), the FAULT signal
will be asserted and latched.
Place shunts on JU4 - JU8 and JU10 (see the
Adjustment and Control Description section for
details).
Remove shunts JU1 and JU2.
To enable the output connect TX_DISABLE to GND
by placing a shunt on JU3.
14) Adjust R2 until the desired laser modulation current
is achieved.
Note: When performing the following resistance
checks, autoranging DMMs may forward bias the onchip ESD protection and cause inaccurate
measurements. To avoid this, manually set the DMM
to a high range.
15) Adjust R14 (RPEAKSET) until the desired amount of
peaking is achieved.
4)
Adjust R15, the RBIASSET potentiometer, for 1.7kΩ
resistance between TP4 (BIASSET) and ground.
5) Adjust R1, the RPWRSET potentiometer, for 10kΩ
resistance between TP2 (REF) and pin 1 (MD) of
JU2.
6) Adjust R14, the RPEAKSET potentiometer, for 20kΩ
resistance between TP10 (PEAKSET) and ground,
to disable peaking.
7) Adjust R16, the RTC potentiometer, for 0Ω resistance
between TP7 (TC1) and TP8 (TC2), to disable
temperature compensation.
8) Adjust R2, the RMODSET potentiometer, for 10kΩ
resistance between TP9 (MODSET) and ground.
9) Apply a differential input signal (250mVP-P to
2200mVP-P) between SMA connectors J5 and J7
(IN+ and IN-).
10) Attach a high-speed oscilloscope with a 50Ω input to
SMA connector J6 (OUT).
11) Connect a +3.3V supply between TP20 (VCC) and
TP21 (GND). Adjust the power supply until the
voltage between TP11 and ground is +3.3V.
12) Adjust R1 (RPWRSET) until desired laser bias current is
achieved.
I
BIAS
=
V
49.9Ω
PIN 1 _ JU 5
13) The MD and BIAS currents can be monitored at TP1
(VPWRMON) and TP3 (VBIASMON) using the equations
below:
IMOD =
Signal Amplitude (V )
50Ω
û'ü5ýHþìÌÿ .ýHñþ For optical evaluation of the MAX3740A, configure the
evaluation kit as follows:
1)
2)
3)
4)
5)
Place shunts on JU2, JU6, JU7, JU8 and JU10 (See
the Adjustment and Control Description section for
details).
Remove components L2 and C9. Remove the shunts
from JU1, JU4 and JU5.
Install a 0Ω resistor at R7 to connect the anode of
the VCSEL to the output.
To enable the output connect TX_DISABLE to GND
by placing a shunt on JU3.
Connect a common cathode VCSEL as shown in
Figure 1. Keep leads short to reduce reflection.
Note: When performing the following resistance
checks, autoranging DMMs may forward bias the onchip ESD protection and cause inaccurate
measurements. To avoid this, manually set the DMM
to a high range.
6)
7)
8)
9)
Adjust R15, the RBIASSET potentiometer, for 1.7kΩ
resistance between TP4 (BIASSET) and ground.
Adjust R1, the RPWRSET potentiometer, for 10kΩ
resistance between TP2 (REF) and pin 1 (MD) of
JU2.
Adjust R14, the RPEAKSET potentiometer, for 20kΩ
resistance between TP10 (PEAKSET) and ground,
to disable peaking.
Adjust R16, the RTC potentiometer, for 0Ω resistance
between TP7 (TC1) and TP8 (TC2), to disable
temperature compensation.
2 ________________________________________________________________________________________
10) Adjust R2, the RMODSET potentiometer, for 10kΩ
resistance between TP9 (MODSET) and ground.
11) Apply a differential input signal (250mVP-P to
2200mVP-P) between SMA connectors J5 and J7
(IN+ and IN-).
12) Attach the VCSEL fiber connector to an
optical/electrical converter.
13) Connect a +3.3V supply between TP20 (VCC) and
TP21 (GND). Adjust the power supply until the
voltage between TP11 and ground is +3.3V.
14) Adjust R1 (RPWRSET) until desired average optical
power is achieved.
15) The MD and BIAS currents can be monitored at TP1
(VPWRMON) and TP3 (VBIASMON) using the equations
below:
V
I =
2×R
PWRMON
I
BIAS
"!$#&%('
=
)*#!
9×V
350Ω
+,
BIASMON
-.
Note: If the voltage at TP1 exceeds VPMTH (typical
0.8V) or TP3 exceeds VBMTH (typical 0.8V), the
FAULT signal will be asserted and latched.
16) Adjust R2 (RMODSET) until the desired optical
amplitude is achieved. Optical amplitude can be
observed on an oscilloscope connected to an
optical/electrical converter. VCSEL overshoot and
ringing can be improved by appropriate selection of
R10 and C10, as described in the Design Procedure
section of the MAX3740 data sheet.
MD
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12
3
45
6
78
9
:5
PWRSET
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COMPONENT
NAME
FUNCTION
D2
Fault Indicator
JU1
COMP
Enables/disables the APC circuit. Remove the shunt to enable the APC circuit.
JU2
PHOTODIODE
Installing a shunt connects the photodiode of the VCSEL to the MD pin. Used
when a VCSEL is installed.
JU3
TX_DISABLE
Enable/disable the output currents. Install a shunt to enable output currents.
JU4
IPD
JU5
APCOPEN
JU6
FAULT
JU7
SQUELCH
JU8
POWER
Installing a shunt provides power to the part.
JU10
VCCEXT
Installing a shunt provides power to the emulation and fault-indicator circuits.
R1
RPWRSET
Adjusts transmit optical power to be maintained by the APC loop.
R2
RMODSET
Adjusts the laser modulation current.
R14
RPEAKSET
Adjusts the peaking for the falling edge of the VCSEL.
R15
RBIASSET
In a closed-loop configuration: adjusts the maximum bias current available to the
APC. In an open-loop configuration: adjusts the bias level of the output.
R16
RTC
The LED is illuminated when a fault condition has occurred (refer to the Detailed
Description section of the MAX3740 data sheet).
Determines the gain of the photodiode emulator. When JU4 is open, the gain is
0.02A/A. When JU4 is shunted, the gain is 0.12A/A.
Installing a shunt connects the electrical output of the part to the emulation circuit.
Installing a shunt enables the external fault-indicator circuit.
Installing a shunt enables the squelch function.
Adjusts the temperature compensation of the modulation current.
_________________________________________________________________________________________
3
JU8
POWER
VCC1
TP11
NOISEGEN
L4
1µH
L3
BLM18HD102SN1
JU10 VCCEXT
VCCEXT
Q3
TP20
VCC
C14
10µF
C15
0.1µF
C16
0.1µF
C18
10µF
C7
0.01µF
C17
0.1µF
JU2
PHOTODIODE
R35
OPEN
VCCEXT
C12
0.01µF
VCC1
5
D2
FAULT
R13
10kΩ
Q2
FMMT491A
JU7
SQUELCH 6
VCC1
R8
4.7kΩ
SQUELCH
8
9
10
11
GND
17
VCC1
16
15
14
13
r w v u t
s r
TP7
TC1
C9
0.1µF
C11
0.01µF
R9
49.9Ω
R7
OPEN
C10
OPEN
12
R10
OPEN
R2 10kΩ
MODSET
TP8
TC2
L2
BLM18HD102SN1
C8
0.01µF
TP9
MODSET
R26
OPEN
R6
10kΩ
R11
49.9Ω
R16 500kΩ
TC
TP5
FAULT
R5
499Ω
R36
OPEN
BIASMON
VCC
MD
COMP
OUT-
C4
0.01µF
R12
499Ω
REF
FAULT
7
JU6
FAULT
OUT+
2
TP4
BIASSET
TP10
PEAKSET
R14 20kΩ
PEAKSET
VCC1
IN-
4
2
4
1
3
D1
VCSEL
PHOTODIODE
J6
OUT
q
Figure 1. MAX3740A EV Kit Schematic Diagram
VCCEXT
VCC
U1
MAX3740A
18
JU4
IPD
R4
2.49kΩ
R34
OPEN
4
BIASSET
R27
OPEN
J7
IN-
IN+
L1
BLM18HD102SN1
BIAS
3
U2
R3
350Ω
19
PEAKSET
C13
0.1µF
20
MODSET
3
21
GND
‚ &€"
(
~ z } | {
z y x
J5
IN+
TP3
BIASMON
TX_DISABLE
TC2
2
C5
0.1µF
GND
22
TC1
1
VCC
~„
 ƒ
JU3
TX_DISABLE
23
PWRMON
24
6
MAX495
TP1
PWRMON
J4
CALOUT-
Q1
FMMT491A
R15 50kΩ
BIASSET
C3
0.047µF
C2
0.1µF
J3
CALIN-
7
C6
0.01µF
TP2
REF
JU1
COMP
J2
CALOUT+
JU5
APCOPEN
R1 10kΩ
PWRSET
C1
0.1µF
J1
CALIN+
4 ________________________________________________________________________________________
TP6
PORTEST
TP21
GND
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Figure 2. MAX3740A EV Kit Component Placement
Guide - Component Side
Figure 3. MAX3740A EV Kit PC Board Layout Solder Side
_________________________________________________________________________________________
5
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Figure 4. MAX3740A EV Kit PC Board Layout Ground Plane
Figure 5. MAX3740A EV Kit PC Board Layout Power Plane
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
6 ___________________ Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
 2003 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.