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19-1061; Rev 1; 1/99
MAX3664 Evaluation Kit
_______________General Description
The MAX3664 evaluation kit (EV kit) simplifies evaluation of the MAX3664 transimpedance preamplifier. The MAX3664 is optimized for hybrid applications that place the preamplifier die in the same package with a photodetector. The EV kit uses a packaged version of the MAX3664 to simplify product evaluation. It allows both optical and electrical testing. The MAX3664's input voltage is determined by internal circuitry. When the input is connected to a photodiode, the MAX3664's input voltage determines the reverse diode voltage. Electrical signal sources connected to the input must be AC coupled. AC coupling the input removes the signal's DC component. Many of the MAX3664's specifications are affected by the average DC input current, which is normally present when the input signal is derived from a photodiode. A current mirror and simple bias-tee are used to create a signal similar to that of a photodiode. The MAX3664 EV kit has several mounting holes for inserting common photodiodes, allowing optical testing.
____________________________Features
Single +3.3V Supply Differential Output Drives 100 Load 590MHz Bandwidth Electrical or Optical Input Provision for User-Supplied Photodiode Fully Assembled and Tested
Evaluates: MAX3664
______________Ordering Information
PART MAX3664EVKIT-SO TEMP. RANGE -40C to +85C BOARD TYPE Surface Mount
______________Component Suppliers
SUPPLIER AVX Central Semiconductor Zetex PHONE (803) 946-0690 (516) 435-1110 (516) 543-7100 FAX (803) 626-3123 (516) 435-1824 (516) 864-7630
_____________________________________________________________Component List
DESIGNATION QTY C1, C9 C2, C3, C8 C4, C5, C6 C7 R1 R2, R3, R6 R4 R5 R7 R8 L1 2 3 3 1 1 3 1 1 1 1 1 DESCRIPTION 33F, 25V tantalum capacitors AVX TAJE336K025R 0.01F, 25V ceramic capacitors 0.1F, 25V ceramic capacitors 390pF, 25V ceramic capacitor 49.9, 1% resistor 200, 5% resistors 2k, 5% resistor 2k, 1% resistor 10k potentiometer 1k, 5% resistor 47H inductor Panasonic ELJ-FA470KF2 DESIGNATION QTY L2, L3 Q1, Q2 D2 U1 J1, J3, J4 JU1, JU2 None None 2 2 1 1 3 2 2 1 DESCRIPTION 4.7H inductors Panasonic ELJ-FA4R7KF2 PNP small-signal transistors Zetex BCX71KCT High-speed switching diode Central Semiconductor CMPD4448 MAX3664ESA SMA connectors (PC edge mount) E.F. Johnson 142-0701-801 2-pin headers Shunts on JU1 and JU2 MAX3664 data sheet
________________________________________________________________ Maxim Integrated Products
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MAX3664 Evaluation Kit Evaluates: MAX3664
_________________________Quick Start
Test Equipment Required
* Signal-source sine-wave generator or network analyzer with range to 650MHz * Signal-source function generator with range to 1MHz * Signal-source pattern generator * Power supply capable of 3.6V, 35mA output with current limit * Oscilloscope with at least 1GHz bandwidth * Wideband noise meter or RF power meter * 470MHz filter with linear phase response (example: Mini Circuits SBLP-467 filter)
Jumper JU2 This jumper grounds the MAX3664's COMP pin. The DC cancellation loop is disabled when COMP is grounded. Potentiometer R7 This potentiometer controls the amount of DC current added to the input signal.
Measurement Information
AC Measurement When making AC measurements, place a shunt on JU1 after setting the DC signal current. Wires attached to this jumper add noise to the signal. DC Measurement For most DC measurements, place a shunt on JU2 to disable the DC cancellation loop. Measure output offset with JU2 open. Low-Frequency Cutoff Measurement The low-frequency cutoff changes with average input current (refer to the MAX3664 data sheet, Typical Operating Characteristics). When measuring lowfrequency cutoff, consider the capacitors in the MAX3664's signal path. When driving a 50 load, capacitors C5 and C6 have a lowpass cutoff of approximately 16kHz. Capacitor C4, driving the 2200 input, has a 720Hz lowpass cutoff. When measuring cutoff frequencies below 50kHz, use a high-impedance oscilloscope to measure the output voltage. With a 1M input, output capacitors C5 and C6 produce a 1.6Hz cutoff frequency, which is low enough not to interfere with the measurement. Noise Measurement Remove R5 before attempting noise measurements to minimize input capacitance. With R5 removed the total capacitance at the IN pin is 1.1pF. Refer to the Designing a Low-Capacitance Input section in the MAX3664 data sheet. Connect an output to a wideband noise meter or a sensitive RF power meter to measure input-referred noise. With 50 output load, the MAX3664's single-ended gain is about 3000 (this can be measured more accurately with an AC gain measurement). Use a filter on the output to limit high-frequency noise. When using an RF power meter, convert the power measurement to input current noise with the following relation: Power x 50 Input Noise Current = Gain
Setup
1) Connect a 3.3V power supply to VCC1 and GND. 2) Remove the shunts from JU1 and JU2. 3) Connect VOUT+ and VOUT- to a dual-channel oscilloscope through terminated 50 cables. 4) Apply a 100mVp-p, 311MHz square wave to VIN. 5) Observe each output of approximately 150mVp-p on the oscilloscope.
_______________Detailed Description
Connections, Adjustments, and Controls
VCC1 Connection This connection provides supply current for the MAX3664. Connect to 3.3V. VCC2 Connection This connection provides supply current for the current mirror that adds the DC component to the input signal. Connect to 3.3V if used. J1-VIN Connection A signal generator can be connected here. This input is terminated with 50 to ground and AC coupled to IN (MAX3664) through series resistors (2200). The AC signal input current to the MAX3664 is VIN/2200. J3-VOUT-, J4-VOUT+ Connection These are the MAX3664 outputs. These connectors are AC coupled to the MAX3664, and connect directly to test equipment with 50 or more input impedance. Jumper JU1 This jumper is in series with the current mirror that adds DC component to the input signal. This is a convenient place to measure the DC input current.
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MAX3664 Evaluation Kit
Photodiode Emulation Use the following relations to simulate a photodiode input with a signal generator and the current mirror (Figure 1):
PAVE = average power = (P1 + P0) / 2 (assuming 50% average duty cycle) re = extinction ratio = P1 / P0 P1 = high signal level = 2PAVE (re) / (re + 1) P0 = low signal level = 2PAVE / (re + 1) P1-P0 = p-p signal amplitude = 2PAVE(re - 1) / (re + 1) Input current is related to optical power by the photodiode responsivity (), as shown in the following equations: IAVE = PAVE x or I=Px For example, follow these steps to emulate a signal with an average power of -20dBm and an extinction ratio of 10: 1) -20dBm optical power will produce 10A of average input current (assume photodiode responsivity of 1A/W). Install a current meter at JU1. Adjust R7 until current is 10A. 2) The signal amplitude is 2P AVE(re - 1) / (re + 1) = 16.3A. To generate this current through the 2200 input resistors, set the signal source to produce an output level of 16.3A x 2200 = 36mVp-p.
P1
Supply Current Supply current, as specified in the MAX3664 data sheet, is the current flowing into VCC1 pad. Current flowing into VCC2 pad powers the current mirror only.
Evaluates: MAX3664
POWER
PAVE
P0
TIME
Figure 1. Optical Power Definitions
Layout Considerations
The EV kit layout has been developed for packaged MAX3664s. The following considerations were taken into account on the evaluation board. 50 controlled impedance traces are used for the VOUT+ and VOUT- signal paths. Power and ground planes are relieved beneath the MAX3664 IN pin to reduce input capacitance.
Using a Photodiode 1) Remove resistor R5 before installing your photodiode in holes provided at location D1. 2) Connect the photodiode anode to IN (pin 2) on the MAX3664. 3) Connect the photodiode cathode to the junction of C8 and R8. 4) Connect the photodiode case ground to INREF1 and INREF2.
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MAX3664 Evaluation Kit Evaluates: MAX3664
JU2 C7 390pF L2 4.7H VCC1 C1 33F 25V L3 4.7H VCC2 C3 0.01F C9 33F 25V R2 200 R3 200 D2 C8 CMPD4448 0.01F C2 0.01F R8 1k D1 PHOTODETECTOR 2 3 1 4 INREF2 GND 5 1 2 VCC COMP 8 C6 0.1F C5 0.1F J3 VOUTSMA J4 VOUT+ SMA
IN MAX3664 OUT- 7 OUT+ 6
3 INREF1
Q1 BCX71KCT
Q2 BCX71KCT 3 2 R7 10k 1 R5 2k NOTE: R5 AND R6 MUST BE INSTALLED AS SHOWN. R6 200
JU1 R4 2k L1 47H C4 0.1F
J1
VIN
GND
SMA R1 49.9
Figure 2. MAX3664 EV Kit Schematic
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MAX3664 Evaluation Kit Evaluates: MAX3664
Figure 3. MAX3664 EV Kit Component Placement Guide-- Component Side
Figure 4. MAX3664 EV Kit PC Board Layout--Component Side
Figure 5. MAX3664 EV Kit PC Board Layout--Ground Plane
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MAX3664 Evaluation Kit Evaluates: MAX3664
Figure 6. MAX3664 EV Kit PC Board Layout--Power Plane
Figure 7. MAX3664 EV Kit PC Board Layout--Solder Side
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MAX3664 Evaluation Kit
NOTES
Evaluates: MAX3664
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_______________________________________________________________________________________
MAX3664 Evaluation Kit Evaluates: MAX3664
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.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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