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19-0454; Rev 1a; 3/96
MAX2450 Evaluation Kit
_______________General Description
The MAX2450 evaluation kit (EV kit) simplifies evaluation of the MAX2450 3V, ultra-low-power quadrature modulator/demodulator. It enables testing of all MAX2450 functions, with no additional support circuitry. The MAX2451 (demodulator) and MAX2452 (modulator) function as subsets of the MAX2450, and can also be evaluated using this EV kit.
____________________________Features
o 130MHz to 160MHz VCO (2x the IF frequency) o Single-Ended Modulator I and Q Inputs o Single-Ended 50 Modulator Output o Single-Ended 50 Demodulator Input o CMOS-Compatible Enable Input o Single-Ended or Differential Demodulator I and Q Outputs
Evaluates: MAX2450/MAX2451/MAX2452
____________________Component List
DESIGNATION QTY C1-C6, C9, C11, C12, C15, C16 C7, C8 C13, C14 11 DESCRIPTION 0.1F, 10% ceramic capacitors Vitramon VJ1206Y104MXX 56pF, 5% ceramic capacitors Vitramon VJ1206A330JXA 0.01F ceramic capacitors Vitramon VJ1206103MXX 10F, 10V, 20% tantalum capacitors Sprague 293D106X001B or AVX TAJB106010 100nH, 10% inductor CoilCraft 1008CS-101XKBC Not included. Use 1H for additional power-supply rejection, if needed. BNC connectors 10k, 5% resistors 56, 5% resistor 47k, 5% resistors 2k potentiometer 5.6k, 5% resistor 49.9, 1% resistor 200, 5% resistor 100k, 5% resistors 3-pin header Varactor Diode M/A-COM MA4ST080CK-287 Maxim MAX2450CWP Maxim MAX436CSD
o Fully Assembled and Tested
______________Ordering Information
PART TEMP. RANGE 0C to +70C BOARD TYPE Surface Mount MAX2450EVKIT-SO
2 2
______________Component Suppliers
SUPPLIER AVX Coilcraft M/A-COM Sprague Vishay/Vitramon PHONE (803) 946-0690 (708) 639-6400 (617) 564-3100 (603) 224-1961 (203) 268-6261 FAX (803) 626-3123 (708) 639-1469 (617) 564-3050 (603) 224-1430 (203) 452-5670
C17, C18, C19
3
L1 L2, L3 Q_IN, I_IN, IF_OUT, IF_IN R1, R4 R2 R3, R5 R6 R17 R18 R19 R23, R24 JU10 D1 U1 U3
1 0 4 2 1 2 1 1 1 1 2 1 1 1 1
_________________________Quick Start
The MAX2450 EV kit is fully assembled and factory tested. Follow the instructions in the Connections and Setup section. * Dual-output function generator capable of generating quadrature signals * Signal generator up to 100MHz * Dual-channel oscilloscope with a 100MHz minimum bandwidth * Low capacitance (<3.0pF) oscilloscope probes (example: Tektronix P6201) * Spectrum analyzer with range 500MHz * Power supplies with 5V and +3V outputs
Test Equipment Required
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAX2450 Evaluation Kit Evaluates: MAX2450/MAX2451/MAX2452
Connections and Setup
General Setup 1) Verify that the shunt on jumper JU10 is in the ENABLE position.
2) Connect the power supplies to the appropriate terminals marked on the EV kit, and apply power. The +3V supply provides power for the MAX2450. The 5V supplies are required only to power the MAX436 buffer amplifier and provide varactor bias. 1) 2) 3) The 70MHz tone is the leakage from LO, with a magnitude typically 36dB below the modulated output. This is due to VBE mismatch of the input transistors internal to the IC. AC coupling of the I and Q signals on the EV kit is used to get the maximum LO suppression. The tone at 69.4MHz is the suppressed sideband signal from the upconversion process, with a magnitude typically 38dB below the desired modulated output. 2) Using the scope to observe the demodulator I and Q channel outputs, you will see that they are 90 degrees offset from each other. Any deviation from 90 degrees is the phase mismatch. The I and Q output amplitudes are approximately 500mVp-p. Any difference in the I and Q output amplitudes produces the amplitude mismatch: Amplitude Mismatch = 20 x log AI AQ
4)
Modulator Setup Connect a cable from the spectrum analyzer to the IF_OUT BNC connector on the EV kit. Set the spectrum analyzer's center frequency to 70MHz and its frequency span to 1MHz/div. Configure the dual-output function generator to the following settings: For Channel 1: A 600kHz sine wave with a 1.2Vp-p amplitude. For Channel 2: A 600kHz sine wave with a 1.2Vp-p amplitude and 90 degrees offset from Channel 1. Connect a cable from Channel 1 of the dual-output function generator to the I_IN BNC input on the EV kit. Similarly, connect a cable from Channel 2 of the dual-function generator to the Q_IN BNC input on the EV kit.
Demodulator Setup 1) Connect a low-capacitance probe from I_OUT (TP2) to Channel 1 of the oscilloscope. TP3 and TP6 are available as ground connections. 2) Connect another low-capacitance probe from Q_OUT (TP5) to Channel 2 of the oscilloscope. 3) Configure the signal generator output from a 50 source to 2.82mVp-p (1mVRMS) at 70.1MHz. 4) Connect a cable from the signal generator to IF_IN on the EV kit.
Low-capacitance probes are recommended for higher-frequency baseband signals (<5MHz). The Tektronix P6201 (or equivalent)--a 1X, 100k probe with less than 3pF of capacitance--is well suited for these applications. 3) To observe the 17.5MHz output of the divide-by-8 prescaler, use a low-capacitance active scope probe (such as the Tektronix P6201) at TP1. A typical scope probe adds too much capacitive load and will slew limit the output. (See the MAX2450 data sheet for a typical output waveform example.) 4) The MAX2450 ENABLE pin connects to VCC through a jumper. To test the power-down function, move the JU10 shunt from the ENABLE to the ENABLE position. This shorts the ENABLE pin to ground. The supply current for the MAX2450 (+3V) should drop below 2A. (Note that this supply current may be affected by leakage from bypass capacitor C17.)
Adjustments and Control
FREQ ADJ The FREQ ADJ potentiometer (R6) controls the frequency of the on-chip oscillator by varying the capacitance of the parallel LC resonant network on the EV kit. Use the following formula to determine the oscillation frequency:
1 2 LEQCEQ
Analysis
1) Using the spectrum analyzer to observe the modulator output spectrum, you will notice three tones. If needed, adjust the oscillator frequency using the FREQ ADJ potentiometer (R6) until there are three tones at 69.4MHz, 70MHz, and 70.6MHz. The tone at 70.6MHz is the desired modulated output signal. Its magnitude should be around -19.8dBm, which translates to 65mVp-p:
dBm - 30
fo =
Vp - p = 2 2 x 50 x 10
20
2
_______________________________________________________________________________________
MAX2450 Evaluation Kit
where LEQ = L1 + LSTRAY and CEQ = 1 1 1 2 + + C7 C8 C VAR + CSTRAY
Evaluates: MAX2450/MAX2451/MAX2452
Table 1. Jumper JU10 Functions
SHUNT LOCATION ENABLE ENABLE ENABLE PIN Connected to VCC Connected to GND MAX2450 Enabled Disabled
Layout Considerations
The MAX2450 EV board can serve as a guide for layout of your board. Make sure the input traces to the I and Q input pins are of equal length and in the same environment as much as possible, to keep the I and Q signals in quadrature for maximum sideband rejection at the modulated output. Lay out the parallel resonant network symmetrically and as close to the IC as possible to minimize the effects of parasitic capacitance. The IF input and output traces should be as short as possible, due to the low signal levels and high frequencies involved. The MAX2450 quadrature demodulator and modulator sections are functionally equivalent to the MAX2451 and MAX2452, respectively. Therefore, the MAX2450 EV kit can be used to evaluate all three parts. Note that the supply currents for the MAX2451 and MAX2452 are lower. The MAX2451 and MAX2452 are not pin compatible with the MAX2450. The MAX2450 is also available in a smaller, QSOP package.
where CVAR is the capacitance of each varactor diode. This EV kit uses a common-cathode dual varactor diode (D1) as a tuning element. Applying different voltages across the diode junction produces different capacitances. The oscillator's frequency tuning range is 130MHz to 160MHz. To alter this range, change the inductance, the capacitance, or both.
Using an External Oscillator The MAX2450 EV kit can be used with an external oscillator by overdriving the on-board VCO. This can be accomplished by removing the varactor diode (D1) and injecting a single-ended signal between C7 and R3. The signal and ground should be connected between C8 and R5. Place a shunt across R5, or remove it completely and shunt it directly on the PC board. The external oscillator amplitude should be 200mVp-p. ENABLE Jumper JU10 controls the MAX2450 enable function. Refer to Table 1 for jumper selection. To use an external control signal, remove the shunt of JU10 completely and connect the external signal to the center pin of JU10. The external control signal should not exceed the MAX2450 supply voltage.
_______________________________________________________________________________________
3
MAX2450 Evaluation Kit Evaluates: MAX2450/MAX2451/MAX2452
+5V C12 0.1F 1 2 3 R23 100k R19 200 4 5 6 C13 0.01F J1 C1 0.1F R24 100k C15 0.1F 7 14 J6 13 12 11 10 9 R17 5.6k 8 J5 CU1 -5V C14 0.01F CU2 R2 56 L2 SHORT C16 0.1F R18 49.9 BNC IF_OUT
V+ IN+ Z+
V+
U3 MAX436
IOUT V+ ISET VN.C. V-
N.C. ZINV-
BNC I_N
BNC IF_IN +3V
C2 0.1F
1 2 3
IF_OUT IF_OUT GND I_IN I_IN Q_IN Q_IN EN PRE_OUT
IF_IN GND VCC
20 19 18 17 16
U1 MAX2450
BNC Q_IN
J2
C3 0.1F
CU3
4 5
I_OUT I_OUT
C11 0.1F TP2
C4 0.1F
6 CU4 7 8 +3V 9
15 Q_OUT 14 Q_OUT LO_GND TANK TANK 13 12 11
I_OUT
TP3
GND
3 JU10 1 2
C5 0.1F TP1 PRE_OUT R1 10k
10 LO_VCC
TP4 TP5
I_OUT Q_OUT
C7 56pF L3 SHORT C6 0.1F R3 47k 1
L1 100nH D1 3 R4 10k +5V 3 JU1
C8 56pF 2 R5 47k TP7 C9 0.1F Q_OUT TP6 GND
+3V +5V C17 10F 10V GND C19 10F 10V C18 10F 10V +3V
R6 2k
-5V
2 1 FREQ_ADJ
Figure 1. MAX2450 EV Kit Schematic
4
_______________________________________________________________________________________
MAX2450 Evaluation Kit Evaluates: MAX2450/MAX2451/MAX2452
Figure 2. MAX2450 EV Kit Component Placement Guide-- Component Side
Figure 3. MAX2450 EV Kit PC Board Layout--Component Side
_______________________________________________________________________________________
5
MAX2450 Evaluation Kit Evaluates: MAX2450/MAX2451/MAX2452
Figure 4. MAX2450 EV Kit PC Board Layout--Ground Plane
Figure 5. MAX2450 EV Kit PC Board Layout--Power Plane
Figure 6. MAX2450 EV Kit PC Board Layout--Solder Side
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_______________________________________________________________________________________
MAX2450 Evaluation Kit Evaluates: MAX2450/MAX2451/MAX2452
NOTES
_______________________________________________________________________________________
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MAX2450 Evaluation Kit Evaluates: MAX2450/MAX2451/MAX2452
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) 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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