19-1790; Rev 0; 9/00 MAX3864 Evaluation Kit The MAX3864 evaluation kit (EV kit) simplifies evaluation of the MAX3864 transimpedance preamplifier. The EV kit includes a circuit that emulates the highspeed, current input signal that would be produced by a photodiode. Features ♦ Fully Assembled and Tested ♦ Includes Photodiode Emulation Circuit Ordering Information The MAX3864 EV kit is fully assembled and tested. PART MAX3864EVKIT-SO TEMP. RANGE -40°C to +85°C Component List DESIGNATION C1, C2, C4, C7 QTY 4 DESCRIPTION Component List DESIGNATION QTY U4, U5 2 User-supplied optical modules J1−J5 5 SMA connectors (edge mount) E.F. Johnson 142-0701-801 or Digi-key J502-ND VCC, +15V, GND 3 Test points Digi-key 5000-ND JU1 1 2-pin header (0.1in centers) Digi-Key S1012-36-ND JU2 1 470pF capacitor (0805) Murata GRM40COG471J050A None 1 Shunt for JU1 Digi-Key S9000-ND None 1 MAX3864 EV kit (Rev. A) circuit board 1000pF ±10%, 25V (min) ceramic capacitors (0603) Murata GRM39X7R102K050A C10, C11 2 1000pF ±10%, 25V (min) ceramic capacitors (0805) Murata GRM40X7R102K050A C3, C5, C6, C12−C17 9 0.1µF ±10%, 25V (min) ceramic capacitors (0603) Murata GRM39X7R104K016A C8, C9 2 33µF ±10%, 25V (min) tantalum capacitors AVX TAJE336K025 R1, R9 2 200Ω ±5% resistors (0603) R2, R10 4 510Ω ±5% resistors (0402) Note: R2 and R10 = two 510Ω resistors in series IC PACKAGE 8 SO DESCRIPTION None 1 MAX3864 data sheet None 1 MAX3864 EV kit data sheet 51Ω ±5% resistors (0603) R3, R11 2 R4, R12 2 1kΩ ±5% resistors (0603) R5 1 1kΩ variable resistor Bourns or Digi-Key 3296W-102-ND R6 1 5kΩ ±5% resistor (0805) 1 10kΩ variable resistor Bourns or Digi-Key 3296W-103-ND 1 L1, L2 Component Suppliers PHONE FAX AVX 843-444-2863 843-626-3123 10kΩ ±5% resistor (0805) Central Semiconductor 516-435-1110 516-435-1824 2 Ferrite beads Murata BLM11A601S Murata 415-964-6321 415-964-8165 U1 1 MAX3864ESA 8-pin SOIC U2 1 CMPT3906 PNP Transistor Central Semiconductor U3 1 MAX400CSA 8-pin SOIC R7 R8 SUPPLIER Note: Please indicate that you are using the MAX3864 when contacting these component suppliers. ________________________________________________________________ Maxim Integrated Products 1 For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. Evaluates: MAX3864 General Description Evaluates: MAX3864 MAX3864 Evaluation Kit Quick Start Table 1. Recommended Resistor Values 1) Remove shunt from jumper JU1. EVALUATION KIT R1, R9 R2, R10 2) Connect a +3.3V supply to the VCC terminal and ground to the GND terminal. MAX3864EVKIT-SO 200Ω (0402) 1020Ω (composed of two 510Ω (0402) resistors) 3) Connect OUT+ and OUT- to the 50Ω inputs of a high-speed oscilloscope. 4) Connect a signal source to INPUT. Set the signal amplitude to 50mVp-p (this may require some attenuation between the source and the MAX3864 EV kit.) The signal should have a data rate between 1000Mbps and 2500Mbps. 5) The differential signal at the oscilloscope should be between 75mVp-p and 150mVp-p. Detailed Description The MAX3864 is designed to accept a DC-coupled input from a high-speed photodiode, with a total amplitude of 10µA to 2mA. Unfortunately, high-speed current sources are not common laboratory equipment. Also, because the MAX3864 provides a DC bias for the photodiode, it cannot be DC-coupled to signal sources. To allow characterization without a photodiode, the MAX3864 EV kit provides a simple circuit that emulates a photodiode using common voltage output signal sources. The connector at INPUT is terminated with 50Ω to ground. This voltage is then AC-coupled to a resistance in series with the MAX3864 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 not to change the bandwidth of the transimpedance amplifier. Surface-mount resistors have parasitic capacitance that reduces their impedance at frequencies above 1GHz. The user should carefully evaluate any changes to R1 and R2. Table 1 shows the recommended resistor values. Photodiode Emulation The following procedure can be used to emulate the high-speed current signal generated by a photodiode: 1) Select the desired average optical power (P AVE) and extinction ratio (re). 2) Calculate the average current (IAVE), and adjust R7 and R5 to obtain it. IAVE = 10(PAVE/10) 1000 ρ ρ = photodiode responsivity in A/W PAVE in dBm IAVE in Amps 3) Calculate the AC signal current, and adjust the signal generator to obtain it. IINPUT = 2 ✕ IAVE(re - 1) / (re + 1) IINPUT in Amps Table 2. Connections, Adjustments, and Control CONTROL Supply Voltage Connection (3.0V to 5.5V, 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. R5 Potentiometer. Fine adjustment of the DC current input. R7 Potentiometer. Coarse adjustment of the DC current input. OUT+, OUTINPUT 2 DESCRIPTION VCC Connections for the MAX3864 Output Signal Input Connection for a Signal Generator _______________________________________________________________________________________ MAX3864 Evaluation Kit J4 +15V Evaluates: MAX3864 C7 1000pF R12 1k C16 0.1µF NO GND PLANE R9 R10 J5 INPUT 200Ω R6 5k 1020Ω C17 0.1µF R11 51Ω 1 2 R5 1k 4 2 3 2 U3 1 3 6 1 U2 3 7 C4 1000pF R4 1k 2 NO GND PLANE C3 0.1µF R1 R2 200Ω 1020Ω R3 51Ω 3 2 OUT+ U5 GND OUT- MAX3864CAN N.C. U1 C5 0.1µF OUT+ J3 MAX3864 OUT- 6 IN FILTER J2 7 OUT+ 5 GND OUTC6 0.1µF C12 0.1µF J12 4 J11 3 4 8 GND VCC JU2 C14 0.1µF VCC VCC2 1 VCC1 INPUT C10 1000pF VCC1 J10 C2 1000pF J1 VCC2 J9 JU1 C1 1000pF 1 C9 33µF 25V FERRITE L2 J7 +15V R8 10k +15V C8 33µF 25V J8 MAX400 3 2 R7 10k FERRITE L1 J6 VCC2 C15 0.1µF 1 C11 1000pF 2 VCC OUT+ U4 GND OUT- MAX3864CAN J13 4 J14 3 C13 0.1µF Figure 1. MAX3864 EV Kit Schematic 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 2IAVE(re - 1) / (re + 1) = 16µA. To generate this current through the 2200Ω input resistors, set the signal source to produce an output level of 16µA ✕ 1220Ω = 20mVp-p. _______________________________________________________________________________________ 3 Evaluates: MAX3864 MAX3864 Evaluation Kit 1.0" Figure 2. MAX3864 EV Kit Component Placement Guide 1.0" Figure 3. MAX3864 EV Kit PC Board Layout—Component Side 4 1.0" Figure 4. MAX3864 EV Kit PC Board Layout—Ground Plane _______________________________________________________________________________________ MAX3864 Evaluation Kit Evaluates: MAX3864 1.0" 1.0" Figure 5. MAX3864 EV Kit PC Board Layout—Power Plane Figure 6. MAX3864 EV Kit PC Board Layout—Solder Side 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________5 © 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.