19-3219; Rev 0, 2/04 MAX3724/MAX3725 Evaluation Kit The MAX3724/MAX3725 evaluation kit (EV kit) allows complete evaluation of both versions of 3.2Gbps transimpedance amplifiers. The EV kit includes a circuit that emulates the high speed, zero-to-peak current input signal that would be produced by a photodiode. The kit also includes a calibration circuit that allows accurate bandwidth measurement. The MAX3724/MAX3725 EV kit is fully assembled and tested. ________________________ Features ♦ Fully Assembled and Tested ♦ Includes Photodiode Emulation Circuit ♦ Calibration Circuit for Accurate Bandwidth Measurement _______________Ordering Information PART TEMP RANGE IC-PACKAGE MAX3724EVKIT -40°C to +85°C Die MAX3725EVKIT -40°C to +85°C Die ________________________________________Electrical Evaluation Component List DESIGNATION QTY C3, C5, C6 3 C4, C7, C8, C10, C11 5 C2 1 C1 1 R3, R4, R11, R12 R5, R8 R6, R7 R9, R10 R13, R14 R15, R16 DESCRIPTION 0.01µF ±10% ceramic capacitors (0201) 0.1µF ±10% ceramic capacitors (0402) 10µF ±10% 10V min ceramic capacitor 33µF ±5% 10V min tantalum capacitor 4 499Ω ±1% resistor (0402) 2 2 4.99kΩ ±1% resistor (0402) 53.6Ω ±1% resistor (0402) 49.9Ω ±1% resistor (0402) MAX3724 EV board Not installed MAX3725 EV board 24.9Ω ±1% resistor (0402) MAX3724 EV board 0Ω shunt resistor (0402) MAX3725 EV board 2 2 2 DESIGNATION QTY L1 1 JU1 1 J3-J7 5 TP1-TP4 4 U1 1 Outside Vendor Supply Outside Vendor Supply None None 1 None 1 DESCRIPTION 56nH inductor Coilcraft 1008CS-560XKBC 2-pin header, 0.1in centers SMA connectors, round, Johnson 142-0701-801 Test Points MAX3724E/D MAX3724 EV board MAX3725E/D MAX3725 EV board 0 1mil Au wire (8 bonds) 0 Epoxy, Ablefilm 84-1 LMI 1 Shunt MAX3724 EV board MAX3725 EV board MAX3724/MAX3725 Data Sheet 10kΩ ±1% resistor (0402) __________________________________________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. Evaluates: MAX3724/MAX3725 _______________ General Description MAX3724/MAX3725 Evaluation Kit _____________Component Suppliers Evaluates: MAX3724/MAX3725 SUPPLIER the transimpedance amplifier is not altered. Surfacemount resistors have parasitic capacitance that may reduce their impedance at frequencies above 1GHz. PHONE FAX AVX 803-946-0690 803-626-3123 ____________Photodiode Emulation Coilcraft 847-639-6400 847-639-1469 Murata 814-237-1431 814-238-0490 The following procedure can be used to emulate the high-speed current signal generated by a photodiode: Note: Please indicate that you MAX3724/MAX3725 when contacting suppliers. are using the these component ________________________Quick Start 1) 1) Connect a signal source to IN at J3. Set the signal amplitude to 100mVp-p (this may require some attenuation between the source and the MAX3724/MAX3725 EV kit.) The signal should have a data rate of 3.2Gbps. Connect OUT+ and OUT- to the 50Ω inputs of a high-speed oscilloscope at J6 and J7. 1) Select the desired optical power (PAVE, dBm) and extinction ratio (re). 2) Calculate the average current (IAVE, A). Set the DC current at TP1 to IAVE. I AVE = 10 ( PAVE / 10) ⋅ρ 1000 (ρ= photodiode responsivity in A/W) 3) Calculate the AC signal current and adjust the signal generator to obtain it. I AC = 2 ⋅ I AVE ⋅ re − 1 re + 1 3) Remove the shunt from jumper JU1. 4) Connect a +3.3V supply to the VCC terminal and ground to the GND terminal. For example: To emulate a photodiode with an average power of –16dBm and an extinction ratio of 10; 5) The differential signal at the oscilloscope should be greater than 280mVp-p (140mVp-p on MAX3724 EV Kit). 1) –16dBm optical power will produce 25µA of average input current (assume photodiode responsivity of 1A/W). Set the DC current input to 25µA at TP1. 2) The signal amplitude is 2 IAVE (re-1)/(re+1)=41µA. To generate this current through the 1000Ω input resistors, set the signal source to produce an output level of ______________Detailed Description The MAX3724/MAX3725 EV kit allows characterisation without a photodiode. The kit is designed to emulate a DC-coupled photodiode input. Diode currents may have 6uApp to 2mApp AC-current with a DC component from 10uA to 1mA. The high-speed current source of the photodiode is emulated on the EV kit using separate AC and DC paths. The AC signal is supplied from a standard 50Ω lab source that delivers power to an on board termination resistor. A current is then generated from the voltage signal by a resistor with low stray capacitance. The effect of the DC photodiode current may be emulated by a current source at TP1. An isolation resistor prevents the DC source from loading the AC path. The values of the series resistive element, R3 and R4, have been carefully selected so that the bandwidth of 41µA*1000 Ω = 41mVp-p. ______________Noise Measurement Remove R3 and R4 before attempting noise measurements to minimize input capacitance. With R3 and R4 removed the total capacitance at the IN pin is approximately 0.85pF. __________________RSSI (MAX3724) The Average Power at the MAX3724 input is indicated by the common mode output measured at TP2 and TP3. Refer to the MAX3724 data sheet for details. _____________________________________Adjustments and Control Descriptions COMPONENT NAME JU1 OFFSET CORRECTION TP1 DC CURRENT INPUT TP2, TP3 OUTPUT COMMON MODE FUNCTION Instal JU1 to disable offset correction. Apply DC current for photodiode simulation. MAX3724 RSSI Signal 2 _________________________________________________________________________________________ MAX3724/MAX3725 Evaluation Kit Evaluates: MAX3724/MAX3725 Figure 1. MAX3724/MAX3725 EV Kit Schematic Figure 2. MAX3724/MAX3725 EV Kit PC Component Placement Guide—Component Side _______________________________________________________ 3 Evaluates: MAX3724/MAX3725 MAX3724/MAX3725 Evaluation Kit Figure 3. MAX3724/MAX3725 EV Kit PC Board Layout—Component Side Figure 5. MAX3724/MAX3725 EV Kit PC Board Layout—Power Plane Figure 4. MAX3724/MAX3725 EV Kit PC Board Layout—Ground Plane Figure 6. MAX3724/MAX3725 EV Kit PC Board Layout—Solder Side 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600___________________4 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products