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19-1112; Rev 0; 8/96
MAX3761 Evaluation Kit
_______________General Description
The MAX3761 evaluation kit (EV kit) simplifies evaluation of the MAX3761 limiting amplifier. It allows easy programming of the loss-of-signal (LOS) threshold. The board layout provides for multiple termination configurations. The circuit includes space for the MAX3760 preamplifier and user-supplied photodiode. Adding these two components to the MAX3761 forms a complete fiber optic receiver.
______________Component Suppliers
SUPPLIER AVX Central Semiconductor Coilcraft Sprague Zetex USA PHONE (803) 946-0690 (603) 224-1961 (847) 639-6400 (516) 435-1110 (516) 543-7100 FAX (803) 626-3123 (603) 224-1430 (847) 639-1469 (516) 435-1824 (516) 864-7630
Evaluates: MAX3761
____________________________Features
(R) Fully Assembled and Tested (R) Easy LOS Threshold Programming (R) Multiple Output Terminations (R) Circuit Includes MAX3760 Preamplifier* (R) Socket for User-Supplied Photodiode Signal
Source
DESIGNATION C1 C2 C3, C5, C7, C9, C30 C4, C6, C8, C10, C11 C12, C13, C14, C15 C16, C17 C26, R24, R28 C29 CAZ1 R2, R3, R15, R16, R19, R20, R23, R27 R4 R5, R40 R6 R7 R8, R10, R11, R14, R17, R18, R21, R22, R26 R9, R13, R41, R42, R44 R12 R25, R29 R37 R38, R39 QTY 1 1 5 5 0 2 3 1 1 8 1 2 1 1 0 5 1 2 1 2 DESCRIPTION 33F, 35V, 10% tantalum cap Sprague 595D336X9035R2 3.3F, 25V, 10% tantalum cap Sprague 595D335X9025B2 0.027F, 25V ceramic capacitors 100pF, 25V ceramic capacitors Open 5600pF, 25V ceramic capacitors 0.1F, 25V ceramic capacitors 390pF, 25V ceramic capacitor 150pF, 16V ceramic capacitor 0 resistors 100k potentiometer 2k, 5% resistors 100k, 5% resistor 5.1k, 5% resistor Open 1k, 5% resistors 100, 5% resistor 330, 5% resistors 49.9, 1% resistor 820, 5% resistors
______________Ordering Information
PART MAX3761EVKIT-SO TEMP. RANGE -40C to +85C BOARD TYPE Surface Mount
_____________________________________________________________Component List
DESIGNATION R43 D3 D4 L1, L2, L3 L4 L5, L6 L7 U1 U2 Q3, Q4 PREAMP, OUT+, OUT-, LOS+, LOSVIN+, VINJU4, JU6, JU7, INV JU3, JU5 VTH, RSSI None None None QTY 1 0 1 3 1 0 1 1 1* 2 5 2 4 2 2 3 1 1 DESCRIPTION 10k potentiometer User-supplied photodiode High-speed switching diode Central Semiconductor CMPD4448BK 5.6H inductors Coilcraft 1008LS-562 4.7H inductor Coilcraft 1008CS-472 Open 15H inductor Coilcraft 1812CS-15XKBC MAX3761EEP MAX3760ESA PNP small-signal transistors Zetex BCX71KCT SMA connectors (edge mount) E. F. Johnson 142-0701-801 SMA connectors (PC mount) 2-pin headers 3-pin headers 1-pin headers Shunts for JU3, JU5, JU6 MAX3761/MAX3762 circuit board MAX3761 data sheet 1
*Contact factory for availability.
________________________________________________________________ Maxim Integrated Products
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAX3761 Evaluation Kit Evaluates: MAX3761
_________________________Quick Start
1) Connect a +5V power supply to the +5V pad, then connect the power-supply ground to the GND pad. 2) Ensure that the JU3 shunt is across pins 1 and 2. 3) Ensure that JU5 and JU4 are open. 4) Ensure that JU7 is shorted. 5) Apply a 100mV signal at VIN+ and VIN-, with a 622Mbps data rate. 6) Connect OUT+ and OUT- to a 50 terminated oscilloscope.
Data Output Terminations
Oscilloscope Connection The MAX3761 EV kit is shipped configured to connect to a 50 terminated oscilloscope. Each output is AC coupled and has a 330 resistor to ground, which provides bias current. PECL Outputs To drive a circuit that requires a PECL input, remove the 330 resistors (R25 and R29) and short the coupling capacitors (R24 and R28), then terminate with 50 to VCC - 2V.
_______________Detailed Description
Data Inputs
Differential Drive from a Signal Generator The MAX3761 EV kit is factory configured with a 100 differential load AC coupled to the MAX3761 inputs. Single-Ended Drive from a Signal Generator Remove R12, install R10 and R11 = 49.9, and connect the signal generator to VIN+. This provides a 50 termination to ground for the signal generator. Differential Input from the Preamplifier The MAX3761 EV kit incorporates the MAX3760 transimpedance amplifier. If the MAX3760 preamplifier is used, connect the +5V supply to the terminal labeled 5V OFFSET. Install shorts in L5 and L6 to connect the preamplifier to the limiting amplifier. Verify that R12 = 100. Connect a signal generator to the preamplifier, or use a photodiode and light source connected at D3. If a photodiode is used, remove R41. Figure 1 shows the proper installation of a user-supplied photodiode.
LOS Outputs
The MAX3761's LOS outputs are TTL compatible, with internal pull-up resistors. Connect the test point LOS+ to a voltmeter or high-impedance probe.
Adjustments and Controls
LOS Voltage Threshold Adjustment Potentiometer R4 adjusts the VTH voltage, which programs the LOS threshold. Refer to the MAX3761 data sheet for details. Preamplifier Offset Current Potentiometer R43 adjusts the amount of offset current at the preamplifier input (for use with the MAX3760 transimpedance amplifier). Refer to the MAX3760 data sheet for details. Jumper JU7 JU7 implements the squelch function. When JU7 is shorted, the LOS+ terminal is connected to the DISABLE pin. When LOS+ is asserted high, the data outputs are disabled. If shorting JU7, remove JU5. Jumper JU3
For normal operation, short pins 1 and 2.
CONNECT ANODE CONNECT CATHODE R41 D3 1 2 VCC IN COMP 8 7
U2 MAX3760
OUT-
Jumper JU5 JU5 sets the voltage at the disable pin. To hold the MAX3761's outputs enabled, short pins 2 and 3. To hold the MAX3761's outputs disabled, short pins 1 and 2. Remove JU5 if JU7 is used. Jumper JU6 JU6 connects a current mirror to the MAX3760 transimpedance amplifier input, allowing DC offset current to be added to the input signal. This is a convenient place to measure the added DC offset current. Jumper JU4 When shorted, JU4 disables the MAX3761's offset correction. This allows DC parameter testing.
3 INREF1 C30 4 INREF2
OUT+ 6 GND 5
R44
CONNECT CASE GROUND
Figure 1. Photodiode Connection
2 _______________________________________________________________________________________
VCC1 C11 100pF VCC1 3 1 VCC2 JU7 J4 2 RSSI LOS+ LOSVCC2 R17 OPEN VCC1 J5 VCC2 SMA R19 0 18 17 16 15 14 13 12 INV R27 0 VTH L1 5.6H L2 5.6H CU1 L3 5.6H L4 4.7H C9 0.027F C10 100pF C7 0.027F C8 100pF VCC4 VCC3 C5 0.027F C6 100pF VCC2 R6 100k C3 0.027F C4 100pF C1 33F 35V C2 3.3F 25V VCC1 R4 100k R29 330 11 VCC2 R26 OPEN R28 0.1F J8 SMA C12 OPEN R23 0 R24 0.1F J6 SMA C13 OPEN R18 OPEN R16 0 EN VCC VCC VCC0 OUT+ OUTGND0 VTH INV VIN+ VINGND SUB CZP CZN 3 4 19 SMA R15 0 20 JU5 2 RSSIB 1 FILTER DISABLE R13 1k J1 VIN+ VCC1 1 2 JU3 3 VCC1 5 C14 OPEN C15 OPEN R12 100 6 7 8 9 J2 JU4 CAZ1 150pF 10 VINC17 5600pF R10 OPEN R3 0 R11 OPEN R20 0 R21 OPEN L6 OPEN C16 5600pF RSSI R14 OPEN
Figure 2. MAX3761 EV Kit Schematic
R7 5.1k R8 OPEN R9 1k
LOS+
PREAMP A
L5 OPEN
R2 0
U1 MAX3761
LOSR22 OPEN VCC2
PREAMP B
OUT-
R25 330
OUT+
+5V
GND
R5 2k
Evaluates: MAX3761
_______________________________________________________________________________________
5V OFFSET
MAX3761 Evaluation Kit
3
MAX3761 Evaluation Kit Evaluates: MAX3761
C29 390pF VCC3 R44 1k 1 2 D3 PHOTODIODE 2 VCC4 R38 820 R39 820 3 D4 C30 CMPD4448 0.027F 1 4 INREF2 GND 5 VCC IN COMP 8 7 PREAMP A PREAMP B
U2 MAX3760
OUT-
3 INREF1
OUT+ 6
Q3 BCX71KCT
Q4 BCX71KCT 3 2 R43 10k 1 R41 1k
JU6 R40 2k L7 15H
R42 1k
PREAMP
J16 SMA
C26 0.1F
R37 49.9
Figure 2. MAX3761 EV Kit Schematic (continued)
Layout Considerations
Note that the EV kit board contains four layers. The layers beneath the MAX3760 inputs were relieved to reduce capacitance at the transimpedance amplifier input. Controlled impedance lines were used for output signal paths.
4
_______________________________________________________________________________________
MAX3761 Evaluation Kit Evaluates: MAX3761
Figure 3. MAX3761 EV Kit PC Board Layout--Component Side
Figure 4. MAX3761 EV Kit PC Board Layout--Ground Plane
Figure 5. MAX3761 EV Kit PC Board Layout--Power Plane
Figure 6. MAX3761 EV Kit PC Board Layout--Solder Side
_______________________________________________________________________________________
5
MAX3761 Evaluation Kit Evaluates: MAX3761
Figure 7. MAX3761 EV Kit Component Placement Guide
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 (c) 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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