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19-2691; Rev 0; 12/02
MAX9981 Evaluation Kit
General Description
The MAX9981 evaluation kit (EV kit) simplifies the evaluation of the MAX9981 825MHz to 915MHz dual high-linearity active down-converter mixer. It is fully assembled and tested at the factory. Standard 50 SMA connectors are included for the inputs and outputs to allow quick and easy evaluation on the test bench. This document provides a list of equipment required to evaluate the device, a straightforward test procedure to verify functionality, a description of the EV kit circuit, the circuit schematic, a bill of materials (BOM) and artwork for each layer of the PC board. Contact MaximDirect sales at 888-629-4642 to check on pricing and availability for these kits. o o o o o o o o o o o
Features
Fully Assembled and Tested +27.3dBm Input IP3 +13.6dBm Input 1dB Compression Point 825MHz to 915MHz RF Frequency 725MHz to 1085MHz LO Frequency 70MHz to 170MHz IF Frequency 2.1dB Conversion Gain 10.8dB Noise Figure 42dB Channel-to-Channel Isolation -5dBm to +5dBm LO Drive Built-In LO Switch with 52dB LO1-to-LO2 Isolation
Evaluates: MAX9981
Component Suppliers
SUPPLIER Coilcraft Digi-Key Johnson Mini-Circuits Murata PHONE WEBSITE PART MAX9981EVKIT 800-322-2645 www.coilcraft.com 800-344-4539 www.digikey.com 507-833-8822 www.johnsoncomponents.com 718-934-4500 www.minicircuits.com 770-436-1300 www.murata.com
Ordering Information
TEMP RANGE -40C to +85C IC PACKAGE 36 QFN-EP* (6mm x 6mm)
*EP = Exposed paddle.
Component List
DESIGNATION C1, C4 QTY 2 DESCRIPTION 33pF 5%, 50V C0G ceramic capacitors (0603) Murata GRM1885C1H330J 3.9pF 0.25pF, 50V C0G ceramic capacitors (0603) Murata GRM1885C1H3R9C 100pF 5%, 50V C0G ceramic capacitors (0603) Murata GRM1885C1H101J 15pF 5%, 50V C0G ceramic capacitors (0603) Murata GRM1885C1H150J 0.033F 10%, 25V X7R ceramic capacitors (0603) Murata GRM188R71E333K 220pF 5%, 50V C0G ceramic capacitors (0603) Murata GRM1885C1H221J 330pF 5%, 50V C0G ceramic capacitors (0603) Murata GRM1885C1H331J DESIGNATION L1-L4 R1, R2 R3-R6 R7 J1-J6 QTY 4 2 4 1 6 DESCRIPTION 560nH 5% wire-wound inductors (1008) Coilcraft 1008CS-561XJBC 267 1% resistors (0603) 137 1% resistors (0603) 47k 5% resistor (0603) PC board edge-mount SMA RF connectors (flat tab launch) Johnson 142-0741-856 4:1 transformers (200:50) Mini-Circuits TC4-1W-7A Large test point for 0.063in PC board (red) Mouser 151-107 Large test point for 0.063in PC board (black) Mouser 151-103 Large test point for 0.063in PC board (white) Mouser 151-101 MAX9981EGX-T*
C2, C3
2
C5, C6, C9, C10
4
C7, C8
2
T1, T2 TP1 TP2 TP3 U1
1 1 1 1 1
C11, C12
2
C13, C16, C17, C20 C14, C15, C18, C19
4
4
*The exposed paddle conductor on U1 must be solder attached to a grounded pad on the circuit to ensure a proper electrical/thermal design. 1
________________________________________________________________ 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.
MAX9981 Evaluation Kit Evaluates: MAX9981
Quick Start
The MAX9981 EV kit is fully assembled and factory tested. Follow the instructions in the Connections and Setup section for proper device evaluation.
Table 1. Test Equipment Required
EQUIPMENT HP E3631A Fluke 75 series II HP/Agilent 8648B HP 437B HP 8561 HP 8482A 3dB pad 50 termination QTY 1 1 3 1 1 1 4 2 DESCRIPTION DC power supply Digital multimeter (ammeter) RF signal generators RF power meter Spectrum analyzer High-power sensor (power head) 3dB attenuators 50 (1W) terminations
Test Equipment Required
Table 1 lists the equipment required to verify the operation of the MAX9981 EV kit. It is intended as a guide only, and some substitutions can be made.
Connections and Setup
This section provides a step-by-step guide for testing the basic functionality of the EV kit. As a general precaution to prevent damaging the outputs by driving high-VSWR loads, do not turn on DC power or RF signals until all connections are made. This procedure is specific to operation with an RF input frequency range of 825MHz to 915MHz, low-side injected LO for a 100MHz IF. Choose the test frequency based on the particular system's frequency plan, and adjust the following procedure accordingly. See Figure 1 for the main mixer test setup diagram. 1) Calibrate the power meter for 870MHz. For safety margin, use a power sensor rated to at least +20dBm, or use padding to protect the power head as necessary. 2) Connect 3dB pads to DUT ends of each of the three RF signal generators' SMA cables. This padding improves VSWR and reduces the errors due to mismatch. 3) Use the power meter to set the RF signal generators according to the following: * RFMAIN signal source: -5dBm into DUT at 870MHz (approximately -2dBm before the 3dB pad) * LO1 signal source: 0dBm into DUT at 770MHz (approximately +3dBm before the 3dB pad) * LO2 signal source: 0dBm into DUT at 771MHz (approximately +3dBm before the 3dB pad) 4) Disable the signal generator outputs. 5) Connect the RF source (with pad) to RFMAIN. 6) Connect the LO1 and LO2 signal sources to the EV kit LO inputs. 7) Measure loss in the 3dB pad and the cable that is connected to IFMAIN. Losses are frequency dependent, so test this at 100MHz (IF frequency). Use this loss as an offset in all output power/gain calculations.
8) Connect this 3dB pad to the EV kit's IFMAIN connector, and connect a cable from the pad to the spectrum analyzer. 9) Connect a 50 terminator to the unused RF input and IF output. 10) Set the DC supply to +5.0V, and set a current limit to around 500mA if possible. Disable the output voltage and connect supply to the EV kit through a low internal resistance ammeter. Enable the supply. Re-adjust the supply to get +5.0V at the EV kit since there will be a voltage drop across the ammeter when the mixer is drawing current. 11) Select LO1 by leaving LOSEL (TP3) unconnected or connecting it to +5V. If left floating, LOSEL will be pulled high by an on-board pullup resistor. 12) Enable the LO and the RF sources. To test the diversity mixer, disable the LO and RF sources, turn off the DC supply and repeat steps 3 through 12, replacing RFDIV for RFMAIN and IFDIV for IFMAIN. Be sure to terminate RFMAIN and IFMAIN with 50 terminators. See Figure 2 for diversity mixer test setup.
Testing the Mixer
Adjust the center and span of the spectrum analyzer to observe the IF output tone at 100MHz. The level should be about -5.4dBm (2.6dB conversion gain, 3dB pad loss). The spectrum analyzer's absolute magnitude accuracy is typically no better than 1dB; therefore, use the power meter to get an accurate output power measurement. There will also be a tone at 99MHz which is due to the LO signal applied to LO2. The amount of suppression between the 100MHz and 99MHz signals is the switch isolation. Connect LOSEL to GND to select LO2. Observe that the IF output level at 99MHz increases while the 100MHz level decreases.
2
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MAX9981 Evaluation Kit
Detailed Description
The MAX9981 is a highly integrated downconverter. RF and LO baluns are integrated on-chip, as well as an LO buffer and a SPDT LO input select switch. The EV kit circuit consists mostly of supply decoupling capacitors and DC-blocking capacitors, allowing for a simple design-in. Resistors R3-R6 affect the gain of the mixer. For a typical 2.0dB gain, 137 resistors are used for R3-R6. Higher mixer gain can be realized by increasing R3-R6 and retuning L1-L4, C14, C15, C18, and C19 for IF impedance matching. For example, R3 through R6 = 250, L1 through L4 = 330nH, C14 = C15 = C18 = C19 = 56pF yields a mixer gain of 4.6dB at 70MHz IF with an IF return loss of 12dB. As the differential IF outputs are relatively high impedance (200), they are more susceptible to component parasitics. It is often good practice to relieve the ground plane directly underneath large components to reduce associated shunt-C parasitics.
Evaluates: MAX9981
Supply Decoupling Capacitors
Ceramic capacitors C5, C6, C9, and C10 are 100pF used for high-frequency bypass on the supply. C13 and C17 are 220pF bypass capacitors for IF frequencies. C16 and C20 are used to provide IF ground for the center tap of T1 and T2. Although called out, replacing C16 and C20 with a short circuit causes little to no change in performance.
LOSEL
The EV kit includes a 47k pullup resistor to allow for easy selection of the LO port. Providing a ground at TP3 selects LO2, while leaving TP3 open selects LO1. To drive TP3 from an external source, follow the limits called out in the MAX9981 data sheet. Logic voltages should not be applied to TP3 without the +5V applied. Doing so can cause the on-chip ESD diodes to conduct and could damage the part.
DC-Blocking Capacitors
The MAX9981 has internal baluns on the RFMAIN, RFDIV, LO1, and LO2 inputs. These inputs have almost 0 resistance at DC. C1 and C4 are 33pF DC-blocking capacitors on the RF ports and C7 and C8 are 15pF DC blocks for the LO ports. C14, C15, C18, and C19 are used to block DC current from flowing into the transformers along with providing flexibility for matching.
Modifying the EV Kit
The RF and LO inputs are broadband matched, so there is no need to modify the circuit for use anywhere in the 825MHz to 915MHz RF range (725MHz to 1085MHz LO range). Retuning for a different IF is as simple as scaling the values of the IF pullup inductors up or down with frequency. The IF outputs look like an open collector with 3.6pF to ground (1.8pF differential) from the chip. This capacitance, along with approximately 5.6pF from the evaluation board, can be resonated out at the frequency of interest by proper selection of the bias inductor (L1-L4). To determine the inductor value use the following equation: fIF = 1 2 L x C
RFBIAS
Bias current for the mixer is set with resistors R1 and R2 (267 1%). This value was carefully chosen for best linearity and lowest supply current through testing at the factory. Changing this value, or using lower tolerance resistors degrades performance.
IF
The MAX9981 employs a differential IF output to offer increased IP2 system performance. The IF outputs look like an open collector with 1.8pF of differential capacitance. Inductors L1-L4 are used to resonate out the onchip and evaluation board capacitance at the IF frequency of interest along with providing a low-resistance path for biasing of the IF amplifier. R3-R6 provide a real impedance used to establish the 200 differential impedance. C14, C15, C18, and C19 provide DC blocking along with adding in the flexibility for tuning. The 4:1 baluns (T1 and T2) transform the 200 differential impedance to 50 single ended for ease of measurement. The EV kit IF is matched for operation over the 70MHz to 100MHz frequency range.
The IF output network is tuned for operation at approximately 70MHz, so a 560nH inductor is used. For lower IF frequencies (i.e., larger component values), maintain the component's Q value at the cost of a larger case size unless it is unavoidable.
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3
MAX9981 Evaluation Kit Evaluates: MAX9981
POWER SUPPLY (AG E3631A) BENCH MULTIMETER (HP 34401A) 291mA 5.0V 500mA (MAX)
(AMMETER) OPEN = LO1 GND = LO2 RF SIGNAL GENERATOR (HP 8648B) 870.000MHz 3dB RFMAIN U1 IFMAIN +5V GND LOSEL 3dB RF SPECTRUM ANALYZER (HP 8561x)
MAX9981
RFDIV 50 LO1 LO2 IFDIV 50
3dB
3dB
RF POWER METER (GIGA 80701A, HP 437B) RF HIGHPOWER SENSOR
RF SIGNAL GENERATOR (HP 8648B) 770.000MHz
RF SIGNAL GENERATOR (HP 8648B) 771.000MHz
Figure 1. MAX9981 EV Kit Main Mixer Test Setup Diagram
Layout Considerations
The MAX9981 evaluation board can be a guide for your board layout. Pay close attention to thermal design and close placement of parts to the IC. The MAX9981 package exposed paddle (EP), conducts heat from the part and provides a low-impedance electrical connection. The EP must be attached to the PC board ground plane with a low thermal and electrical impedance contact.
Ideally, this can be achieved by soldering the backside package contact directly to a top metal ground plane on the PC board. Alternatively, the EP can be connected to a ground plane using an array of plated vias directly below the EP. Depending on the ground plane spacing, large surface-mount pads in the IF path may need to have the ground plane relieved under them to reduce shunt capacitance.
4
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MAX9981 Evaluation Kit Evaluates: MAX9981
POWER SUPPLY (AG E3631A) BENCH MULTIMETER (HP 34401A) 291mA 5.0V 500mA (MAX)
(AMMETER) OPEN = LO1 GND = LO2 RF SIGNAL GENERATOR (HP 8648B) 870.000MHz 50 +5V RFMAIN U1 GND LOSEL IFMAIN 50 RF SPECTRUM ANALYZER (HP 8561x)
MAX9981
3dB RFDIV LO1 LO2 IFDIV 3dB
3dB
3dB
RF POWER METER (GIGA 80701A, HP 437B) RF HIGHPOWER SENSOR
RF SIGNAL GENERATOR (HP 8648B) 770.000MHz
RF SIGNAL GENERATOR (HP 8648B) 771.000MHz
Figure 2. MAX9981 EV Kit Diversity Mixer Test Setup Diagram
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5
MAX9981 Evaluation Kit Evaluates: MAX9981
C14 330pF 4:1 (200:50) TRANSFORMER 5.0V TP1 +5V TP2 GND C13 220pF 5.0V L1 560nH R3 137 3 2 L2 560nH R4 137 C16 220pF 1 4 T1 6 J2 SMA IFMAIN
5.0V C15 330pF
5.0V
IFMAIN+
IFMAIN-
GND
GND
GND
GND
VCC
36
35
34
33
32
31
30
29
J1 SMA RFMAIN C11 0.033F
C1 33pF RFMAIN TAPMAIN C2 3.9pF R1 267 MAINBIAS GND GND R2 267 C12 0.033F C3 3.9pF GND DIVBIAS TAPDIV RFDIV C4 33pF 5.0V 1 2 3 4 5 6 7 8 9
28
GND
C5 100pF
C10 100pF
VCC
C8 15pF 27 LO2 GND GND GND LOSEL GND VCC GND LO1 C7 15pF R7 5.0V 47k
U1
J3 SMA LO2
26 25 24 23 22 21 20 19
MAX9981
TP3 LOSEL
J6 SMA RFDIV
J4 SMA LO1
10
11
12
13
14
15
16
17 GND
IFDIV+
GND
GND
GND
VCC
IFDIV-
VCC
GND
18
5.0V
C6 100pF
C9 100pF
C19 330pF 4:1 (200:50) TRANSFORMER T2 3 6 2
5.0V
L4 560nH
R6 137
J5 SMA IFDIV
C17 220pF
L3 560nH
C20 R5 220pF 137
1
4
C18 330pF
Figure 3. MAX9981 EV Kit Schematic 6 _______________________________________________________________________________________
MAX9981 Evaluation Kit Evaluates: MAX9981
1.0"
Figure 4. MAX9981 EV Kit PC Board Layout--Top Silkscreen
1.0"
Figure 5. MAX9981 EV Kit PC Board Layout--Top Soldermask
1.0"
Figure 6. MAX9981 EV Kit PC Board Layout--Top Layer Metal
1.0"
Figure 7. MAX9981 EV Kit PC Board Layout--Inner Layer 2 (GND)
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7
MAX9981 Evaluation Kit Evaluates: MAX9981
1.0"
Figure 8. MAX9981 EV Kit PC Board Layout--Inner Layer 3 (Routes)
1.0"
Figure 9. MAX9981 EV Kit PC Board Layout--Bottom Layer Metal
1.0"
Figure 10. MAX9981 EV Kit PC Board Layout--Bottom Soldermask
1.0"
Figure 11. MAX9981 EV Kit PC Board Layout--Bottom Silkscreen
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) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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