19-2154; Rev 0; 8/01 MAX3825 Evaluation Kit Features ♦ Fully Assembled and Tested ♦ Includes Photodiode Emulation Circuit Ordering Information Component List DESIGNATION QTY PART DESCRIPTION C2, C5, C8, C11, C17–C24, C26, C27 14 0.1µF ±10% ceramic capacitors (0402) Murata GRM36X7R104K010A C3, C6, C9, C12–C16, C28 9 0.01µF ±10% ceramic capacitors (0402) Murata GRM36X7R103K016A C25 1 10µF ±10% tantalum capacitor AVX TAJC106K016 R1, R5, R9, R13, R18 5 681Ω ±1% resistors (0402) R2, R6, R10, R14, R19 5 221Ω ±1% resistors (0402) R3, R7, R11, R15, R20 5 4.99kΩ ±1% resistors (0402) R4, R8, R12, R16, R21 5 53.6Ω ±1% resistors (0402) R17 0 Not installed L1 1 56nH inductor Coilcraft 0805HT-56NTKBC MAX3825EVKIT J1–J4, J15 5 SMA connectors (PC-mount) 9 SMA connectors (edge-mount) TP1–TP4, J13, J14 6 Test points U1 1 None 1 MAX3825U/D die MAX3825 Rev C EV kit circuit None 1 MAX3825 EV kit data sheet None 1 MAX3825 data sheet None — 1mil Au wire for bond pad wiring None — Conductive epoxy 0°C to +85°C IC PACKAGE Dice Component Suppliers SUPPLIER J5–J12, J16 TEMP. RANGE PHONE FAX AVX 843-946-0238 843-626-3123 Coilcraft 847-639-6400 847-639-1469 Murata 770-436-1300 770-436-3020 Note: Please indicate that you are using the MAX3825 when contacting these component 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 Evaluates: MAX3825 General Description The MAX3825 evaluation kit (EV kit) simplifies the evaluation of the MAX3825 quad transimpedance amplifier. The EV kit includes a circuit that emulates the high-speed current input signal produced by a photodiode array. The MAX3825 EV kit is fully assembled and tested. Evaluates: MAX3825 MAX3825 Evaluation Kit Quick Start 1) Connect a signal source to the input of channel 1, J1. Set the signal amplitude to 50mVp-p (this may require some attenuation between the source and the MAX3825 EV kit). The signal should have a data rate of 2.488Gbps. 2) Connect the differential CML outputs of channel 1, J11 and J12, to the 50Ω inputs of a high-speed oscilloscope. 3) Connect a +3.3V supply to the VCC terminal and ground to the GND terminal. 4) The differential signal at the oscilloscope should be between 150mVp-p and 250mVp-p. Detailed Description The MAX3825 EV kit evaluates a MAX3825 quad transimpedance amplifier (TIA) DC-coupled to a high-speed photodiode array with an input current of 10µAp-p to 2mAp-p. This EV kit allows characterization without using a photodiode array by providing a simple circuit that emulates the array’s photocurrent using standard 50Ω test equipment. Each channel’s input transmission line is terminated with 50Ω to ground and AC-coupled into a resistive network. The TIA’s AC input current component is found by dividing the input signal by a voltage-to-current converting 902Ω series resistance. The DC bias current component is adjusted by a separate DC reference (applied to TPn (n = 1, 2, 3, 4) used to set the extinction ratio of a channel’s input signal. The values of the series resistive elements R1, R2, R5, R6, R9, R10, R13, and R14 have been carefully selected not to change the bandwidth of the transimpedance amplifier. Surface-mount resistors may have parasitic capacitance that reduces their impedance at frequencies above 1GHz. The user should carefully evaluate any changes to input series resistors using the calibration network provided on the EV kit. Photodiode Emulation The following procedure can be used to estimate the high-speed current signal generated by a photodiode: 1) Select the desired optical power (PAVE in dBm) and extinction ratio (re). 2) Calculate the average current (I AVE in A), and adjust a DC reference in series with an ammeter connected to TPn (n = 1, 2, 3, 4) until the proper bias current is obtained: IAVE = 10(PAVE / 10) 1000 ✕ ρ (ρ = photodiode responsivity in A/W) Calculate the AC signal current amplitude, and adjust the signal generator to obtain it. IINPUT = 2 ✕ IAVE (re − 1) (re + 1) For example: 1) Emulate a signal with an average power of -13dBm and an extinction ratio of 10 on channel 1. 2) -13dBm optical power will produce 50µA of average input current (assume photodiode responsivity ρ = 1A/W). Connect a power supply in series with an ammeter to TP1. Adjust the power supply until the ammeter reads 50µA. 3) The signal amplitude is 2 ✕ IAVE(re - 1)/(re + 1) = 82µAp-p. To generate this current through the 902Ω input resistors, set the signal source to produce an output level of 82µA ✕ 902Ω = 74mVp-p. Table 1. Connections and Adjustments CONNECTION J1–J4 Inputs (IN1, IN2, IN3, IN4) J5–J12 50Ω CML outputs from the MAX3825 (OUT4+, OUT4-, OUT3+, OUT3-, OUT2+, OUT2-, OUT1+, OUT1-) VCC (J13) Power-supply connection pin. Connect a +3.3V power supply. GND (J14) Ground J15 J16 TP1–TP4 2 DESCRIPTION Calibration strip input Calibration strip output Input bias current voltage supply (IN1, IN2, IN3, IN4) _______________________________________________________________________________________ R16 53.6Ω J4 R12 53.6Ω J3 R8 53.6Ω J2 R4 53.6Ω J1 TP4 R15 4.99kΩ C11 0.1µF TP3 R11 4.99kΩ C8 0.1µF TP2 R7 4.99kΩ C5 0.1µF TP1 R3 4.99kΩ C2 0.1µF C12 0.01µF R14 221Ω C9 0.01µF R10 221Ω C6 0.01µF R6 221Ω C3 0.01µF R2 221Ω R13 681Ω R9 681Ω R5 681Ω R1 681Ω 13 12 11 10 9 8 7 6 5 4 3 2 1 44 43 15 VCC1 VCCI4 14 GNDI1 N.C. GNDI4 N.C. FILT4 IN4 FILT3 IN3 FILT2 IN2 FILT1 IN1 FILTER N.C. N.C. VCCFILT 42 40 ENABLE 18 GNDI3 17 16 C13 0.01µF 39 GNDI2 GNDF MAX3825 U1 VCCI2 VCCI3 VCCI1 41 VCC1 38 19 GNDO3 GNDO1 37 20 GNDO4 VCCO4 OUT4- OUT4+ VCCO4 VCCO3 OUT3- OUT3+ VCCO3 VCCO2 OUT2- OUT2+ VCCO2 VCCO1 OUT1- OUT1+ VCCO1 GNDO2 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 VCC1 C14 0.01µF C18 0.1µF VCC1 J6 J8 J10 J12 VCC1 C17 0.1µF C19 J7 0.1µF C20 0.1µF VCC1 C21 J9 0.1µF C22 0.1µF VCC1 C23 J11 0.1µF C24 0.1µF C15 0.01µF J5 J15 R21 53.6Ω R20 4.99kΩ C27 0.1µF J14 J13 C28 0.01µF R19 221Ω L1 56nH IND0805 R17 OPEN R18 681Ω C26 0.1µF J16 C25 10µF VCC1 Evaluates: MAX3825 C16 0.01µF MAX3825 Evaluation Kit Figure 1. MAX3825 Evaluation Kit Schematic _______________________________________________________________________________________ 3 Evaluates: MAX3825 MAX3825 Evaluation Kit 1.0" Figure 2. MAX3825 Evaluation Kit Component Placement Guide—Component Side 4 _______________________________________________________________________________________ MAX3825 Evaluation Kit Evaluates: MAX3825 1.0" Figure 3. MAX3825 Evaluation Kit PC Board Layout—Component Side _______________________________________________________________________________________ 5 Evaluates: MAX3825 MAX3825 Evaluation Kit 1.0" Figure 4. MAX3825 Evaluation Kit PC Board Layout—Ground Plane 6 _______________________________________________________________________________________ MAX3825 Evaluation Kit Evaluates: MAX3825 1.0" Figure 5. MAX3825 Evaluation Kit PC Board Layout—Power Plane _______________________________________________________________________________________ 7 Evaluates: MAX3825 MAX3825 Evaluation Kit 1.0" Figure 6. MAX3825 Evaluation 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. 8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.