19-1622; Rev 0; 1/00 MAX3665 Evaluation Kit Features ♦ Fully Assembled and Tested ♦ Includes Photodiode Emulation Circuit ♦ Calibration Circuit for Accurate Bandwidth Measurements The MAX3665 EV kit is fully assembled and tested. Ordering Information PART MAX3665EVKIT Component List DESIGNATION QTY TEMP. RANGE IC PACKAGE -40°C to +85°C 8 µMAX Component Suppliers DESCRIPTION PHONE FAX AVX 843-444-2863 843-626-3123 0.1µF 10%, 10V min ceramic caps Central Semiconductor 516-435-1110 516-435-1824 33µF ±10%, 16V min tantalum caps AVX TAJC336K016 Murata 770-684-7821 – Zetex 516-543-7100 516-864-7630 C1, C2, C4, C7, C10, C11 6 1000pF ±10%, 25V min ceramic capacitors C3, C5, C6, C12–C16 8 C8, C9 2 C17, C20, C23 3 5pF ±0.1pF, 50V capacitors C18, C19, C21 3 4pF ±0.1pF, 50V capacitors J1–J5 5 SMA connectors (edge mount) J11–J14 4 Open JU1, JU2 2 2-pin headers (0.1in centers) L1, L2 2 Ferrite beads Murata BLM11HA601S SUPPLIER Note: Please indicate that you are using the MAX3665 when contacting these component suppliers. Quick Start 1) Connect a signal source to INPUT. Set the signal amplitude to 50mVp-p (this may require some attenuation between the source and the MAX3665 EV kit). The signal should have a data rate up to 622Mbps. L3–L8 6 22nH ±5% inductors R1, R9 2 2kΩ ±1% resistors R2, R4, R10, R12 2) Connect OUT+ and OUT- to the 50Ω inputs of a high-speed oscilloscope. 4 1kΩ ±1% resistors 3) Remove shunts from jumpers JU1 and JU2. R3, R11 2 49.9Ω ±5% resistors 4) Connect a +3.3V or +5.0V supply to the VCC terminal and ground to the GND terminal. R5 1 1kΩ potentiometer R6, R8 2 10kΩ ±5% resistors R7 1 10kΩ potentiometer U1 1 MAX3665EUA (8-pin µMAX) U2 1 CMPT3906 PNP transistor U3 1 MAX400CSA (8-pin SO) U4, U5 0 User-supplied optical modules VCC, +15V, GND 3 Test points None 2 Shunts for JU1, JU2 None 1 MAX3665 evaluation kit (rev B) circuit board None 1 MAX3665 data sheet 5) The differential signal at the oscilloscope should be between 100mVp-p and 150mVp-p. Detailed Description The MAX3665 is designed to accept a DC-coupled input from a photodiode with an amplitude up to 450µA peak-to-peak. Because the MAX3665 provides a DC bias for the photodiode, it cannot be DC-coupled to signal sources. To allow characterization without a photodiode, the MAX3665 EV kit provides a simple circuit that emulates a photodiode using common voltage output signal sources. ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. Evaluates: MAX3665 General Description The MAX3665 evaluation kit (EV kit) simplifies evaluation of the MAX3665 transimpedance preamplifier. The EV kit includes a circuit that emulates the zero-to-peak current input signal that would be produced by a photodiode. It also includes a calibration circuit that allows accurate bandwidth measurements. Evaluates: MAX3665 MAX3665 Evaluation Kit The connector at INPUT is terminated with 50Ω to ground. This voltage is then AC-coupled to a resistance in series with the MAX3665’s input, creating an input current. U2 and U3 form a simple DC current source that is used to apply a DC offset to the input signal. The values of the series resistive elements, R1 and R2, have been carefully selected so as not to change the bandwidth of the transimpedance amplifier. Surfacemount resistors have parasitic capacitance that reduces their impedance at frequencies above 1GHz. The user should carefully evaluate any changes to R1 and R2 using the calibration network provided on the EV kit. Photodiode Emulation The following procedure can be used to emulate the high-speed current signal generated by a photodiode: 1) Select the desired optical power (PAVG in dBm) and extinction ratio (re). 2) Calculate the average current (IAVE in Amps) as follows, and adjust R7 and R5 to obtain it: IAVG = (PAVG/10)ρ 3) Calculate the AC signal current (IINPUT in Amps) as follows, and adjust the signal generator to obtain it: IINPUT = 2 · IAVG(re - 1) / (re + 1) For example: 1) Emulate a signal with an average power of -20dBm and an extinction ratio of 10. 2) -20dBm optical power will produce 10µA of average input current (assume photodiode responsivity of 1A/W). Install a current meter at JU1. Adjust R7 and R5 until the current is 10µA. 3) The signal amplitude is IAVG(re - 1) / (re + 1) = 16µA. To generate this current through the 3000Ω input resistors, set the signal source to produce an output level of 16µA · 3000Ω = 48mVp-p. Noise Measurement Remove R2 before attempting noise measurements to minimize input capacitance. With R2 removed, the total capacitance at the IN pin is approximately 0.5pF. Refer to the MAX3665 data sheet for more information. 10 1000 where ρ = photodiode responsivity in A/W. Table 1. Connections, Adjustments, and Control CONTROL VCC Supply Voltage Connection (+3.3V or +5V, 100mA current limit) +15V Supply Voltage Connection for Photodiode Emulator Circuit (+15V, 25mA) GND Connection for Ground JU1 When shunted, the photodiode emulation circuit is active. This is a convenient location to measure the emulated photodiode current. JU2 Test Pin. Shunting JU2 disables the MAX3665 DC cancellation amplifier. R5 Potentiometer. Fine adjustment of the DC current input. R7 Potentiometer. Coarse adjustment of the DC current input. OUT+, OUTINPUT 2 DESCRIPTION Connections for the MAX3665 Output Signal Input Connection for a Signal Generator _______________________________________________________________________________________ _______________________________________________________________________________________ VCC2 +15V 3 1 3 C10 1000pF R8 10k R7 10k R5 1k 1 2 1 +15V 2 2 GND VCC U3 7 MAX400 4 U5 OUT+ OUT- J1 3 4 C21 4pF C1 1000pF C4 1000pF INPUT 3 2 L8 22nH U2 R4 1k INPUT J4 C15 0.1µF J11 R1 2k J12 R2 1k NO GND PLANE C14 0.1µF JU1 3 2 C23 5pF L7 22nH R3 49.9Ω C3 0.1µF 6 1 R6 10k VCC2 VCC1 C11 1000pF JU2 C2 1000pF R11 49.9Ω C16 0.1µF 4 3 2 1 R12 1k U1 OUT- GND FERRITE L2 J8 GND FERRITE L1 FILT 2 1 GND VCC OUT+ OUTU4 GND N.C. MAX3665 OUT+ IN VCC J7 VCC J6 +15V NO GND PLANE R10 R9 1k 2k 3 4 5 6 7 8 C19 4pF C18 4pF C9 33µF 25V C8 33µF 25V J5 L6 22nH C20 5pF L5 22nH L4 22nH L3 22nH J10 J9 VCC2 VCC1 C5 0.1µF C13 0.1µF C12 0.1µF J14 C6 0.1µF C17 5pF +15V OUT+ J13 J3 J2 NOTE: VCC1 AND VCC2 ARE INTERNAL POWER CONNECTIONS. OUT- Evaluates: MAX3665 C7 1000µF MAX3665 Evaluation Kit Figure 1. MAX3665 EV Kit Schematic 3 Evaluates: MAX3665 MAX3665 Evaluation Kit 1.0" Figure 2. MAX3665 EV Kit Component Placement Guide 1.0" Figure 3. MAX3665 EV Kit PC Board Layout—Component Side 4 1.0" Figure 4. MAX3665 EV Kit PC Board Layout—Ground Plane _______________________________________________________________________________________ MAX3665 Evaluation Kit Evaluates: MAX3665 1.0" 1.0" Figure 5. MAX3665 EV Kit PC Board Layout—Power Plane Figure 6. MAX3665 EV Kit PC Board Layout—Solder Side _______________________________________________________________________________________ 5 Evaluates: MAX3665 MAX3665 Evaluation Kit NOTES 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 © 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.