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MAX2690 Evaluation Kit
_______________General Description
The MAX2690 evaluation kit (EV kit) simplifies the evalu-
ation of the MAX2690 downconverter mixer. It enables
testing of all MAX2690 functions, with no additional
support circuitry. Inputs and outputs utilize SMA con-
nectors for ease of connection to test equipment. The
MAX2690 EV kit contains matching components for
operation with a 1.95GHz RF input; however, these
components may be changed for matching to other fre-
quencies from 400MHz to 2.5GHz.
____________________________Features
o
2.7V to 5.5V Single-Supply Operation
o
Low-Power Shutdown Mode
o
Differential IF Port
o
50Ω Broadband LO Port
o
Customizable Gain and Linearity
Evaluates: MAX2690
______________Ordering Information
____________________Component List
DESIGNATION QTY
C1
C2, C3
C4, C5
C6, C7, C8,
C15, C16,
C24, C25, C26
C17
C27
J1, J2
J3, J4
JU1
JU1
L1
L2
L3, L4
R2, R3, R4
R6, R7
R8, R9
R14
U1
None
None
1
2
2
DESCRIPTION
0.5pF, 25V, 10% ceramic capacitor
(0603 footprint)
1pF, 25V, 10% ceramic capacitors
(0603 footprint)
1000pF, 25V, 10% ceramic capacitors
(0603 footprint)
1000pF, 25V, 10% ceramic capacitors
10µF, 16V, ±10% tantalum capacitor
AVX TAJC-106K016
0.1µF, 25V, 10% ceramic capacitor
(0603 footprint)
SMA connectors (edge mount)
SMA connectors (PC mount)
3-pin header (0.1" center)
Shunt
27nH inductor
Toko LL1608-FN27NK
3.3nH inductor
Toko LL1608-FN3N3K
220nH inductors
Coilcraft 0805CS-221XKBC
Not installed
499Ω, 1% resistors
453Ω, 1% resistors
100Ω, 5% resistor
MAX2690EUB
MAX2690 circuit board
MAX2690 data sheet
PART
MAX2690EVKIT
TEMP. RANGE
-40°C to +85°C
BOARD TYPE
Surface Mount
______________Component Suppliers
SUPPLIER
AVX
Coilcraft
Toko America
PHONE
(803) 946-0690
(847) 639-6400
(708) 297-0070
FAX
(803) 626-3123
(847) 639-1469
(708) 699-1194
8
1
1
2
2
1
1
1
1
2
0
2
2
1
1
1
1
_________________________Quick Start
The MAX2690 EV kit is fully assembled and factory test-
ed. Follow the instructions in the
Connections and
Setup
section.
Test Equipment Required
1) DC power supply capable of supplying 2.7V to 5.5V.
2) HP8561E spectrum analyzer or equivalent high-
sensitivity spectrum analyzer capable of operation
to at least 2GHz.
3) Digital multimeter (DMM) to monitor DC supply cur-
rent and voltage, if desired.
4) Two RF signal generators capable of generating
signals up to 2.5GHz for the LO and RF signals
(HP8648C or equivalent).
5) Balun (optional): transformer to convert the
MAX2690’s differential IF output to single-ended
output for ease of measurement (Anzac H-9 or
equivalent).
6) 50Ω terminator.
NOTE: All resistors and capacitors have a 0805 footprint, unless
otherwise noted.
________________________________________________________________
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 408-737-7600 ext. 3468.
MAX2690 Evaluation Kit
Evaluates: MAX2690
Connections and Setup
1) Connect the +2.7V to +5.5V power supply between
V
CC
and GND, and set the voltage to 3.0V.
2) Verify that the shunt on jumper JU1 (SHDN)
is con-
nected between pins 1 and 2 on JU1 (SHDN = V
CC
).
Placing the shunt between pins 2 and 3 on JU1
(SHDN = GND) puts the MAX2690 into low-current
shutdown mode.
3) Connect a balun to the differential IF port. IF+ goes
to the balun’s 0° input, and IF- goes to the 180° input.
Connect the appropriate end of the balun to the
spectrum analyzer, and terminate the remaining port
with the 50Ω terminator, if required.
If a balun is not available, connect IF+ directly to the
spectrum analyzer, and connect the 50Ω terminator
directly to IF-; however, a 6dB decrease in gain will
be observed.
4) Connect a high-frequency signal generator to the
LO input port. Set the LO frequency to 1.75GHz and
the power level to -3.0dBm.
5) Connect a high-frequency signal generator to the
RF input port. Set the RF frequency to 1.95GHz and
the power level to -25.0dBm. This sets the IF fre-
quency to 200MHz.
Conversion gain = (P
OUT
- P
IN
) + mismatch loss
= (-29dBm - -25dBm) + 10dB
Therefore, conversion gain = 6.0dB.
If a balun is not used, increase the mismatch loss from
10dB to 16dB.
These calculations assume no additional loss in the
balun or cables. For maximum accuracy, these losses
must be taken into account.
Mismatch Loss
The 10dB figure for mismatch loss was calculated as
shown in the following equations. These calculations are
shown for single-ended IF operation; however, the equa-
tions for differential operation are identical (see Figure 1).
The open-collector AC output current is represented by
“i” in these equations.
i
2
•
R
6
P
A
=
= power available from MAX2690
4
i
•
R
6
P
D
=
R
6
+ R
8
+ R
L
2
•
R
L
= power delivered to
spectrum analyzer
P
Mismatch loss = - 10log
D
dB
P
A
4
•
R
6
•
R
L
dB
= - 10log
2
R
6
+ R
8
+ R
L
4
•
499
Ω
•
50
Ω
dB
= - 10log
2
499
Ω
+ 453
Ω
+ 50
Ω 
= - (-10dB)
Analysis
1) Set the spectrum analyzer’s center frequency to
200MHz and the total frequency span to 1MHz.
2) Read the peak output power at 200MHz. This power
level should be approximately -29dBm. If a balun is
not used at IF+ and IF-, the output power will be
approximately 6dB lower (-35dBm).
3) The MAX2690’s IF port typically presents a 1kΩ dif-
ferential source impedance (500Ω per side, single
ended). For ease of measurement with 50Ω test
equipment, a resistive-matching network is used on
the EV kit. This network has attenuation that must be
compensated for when calculating the mixer’s true
conversion gain. To calculate conversion gain, the
mismatch loss from the 500Ω IF output (single
ended) to the 50Ω spectrum analyzer input must be
taken into account. The MAX2690’s IF output is an
open-collector configuration with output impedance
at high frequency dominated by 499Ω, external pull-
up resistors (R6 and R7). The 50Ω spectrum analyzer
input is resistively matched with series 453Ω resistors
(R8 and R9). This yields a mismatch loss of 10dB,
which can be compensated for in calculating the
conversion gain as shown in the following equation:
(
(
)
)
Mismatch loss = 10dB
These calculations assume that the capacitance at the
MAX2690’s IF output is resonated with the output induc-
tors (L3 and L4) so that the output impedance at the IF
frequency is dominated by the external pull-up resistors
(R6 and R7).
___900MHz and 2.45GHz Operation
The MAX2690 EV kit is shipped for use at 1.95GHz. The
EV kit can be modified for use over a much wider fre-
quency range (f
RF
= 400MHz to 2.5GHz). Example
RFIN matching networks are shown in Figure 3 for
900MHz operation and Figure 4 for 2.45GHz operation.
Consult the MAX2690 data sheet for information on
matching this input to other frequencies.
2
_______________________________________________________________________________________
MAX2690 Evaluation Kit
Evaluates: MAX2690
V
CC
LGND
SHDN
MAX2690
GND
IFOUT+
L3
220nH
R6
499Ω
C7
i
R8
453Ω
IF+ SMA
SPECTRUM
ANALYZER
RL
50Ω
RL
50Ω
RFIN
IFOUT-
i
L4
220nH
C8
R7
499Ω
R9
453Ω
IF- SMA
RFBYP
GNDLO
V
CC
LO
V
CC
50Ω
TERMINATOR
MAX2690 EVKIT
Figure 1. IF Output Schematic
C26
1000pF
1
C17
10µF
JU1
2
3
C25
1000pF
J3
IF+
V
CC
V
CC
GND
R2
(OPEN)
U1
1
LGND
SHDN
10
R14
100Ω
R8
453Ω
C7
1000pF
C15
1000pF
L3
220nH
C24
1000pF
R3
(OPEN)
C3
1pF
C2
1pF
C4
1000pF
L2
3.3nH
C1
0.5pF
L1
27nH
2
MAX2690
GND
IFOUT+
9
R6
499Ω
R7
499Ω
V
CC
C16
1000pF
J1
RFIN
3
RFIN
IFOUT-
8
4
V
CC
RFBYP
GNDLO
7
C8
1000pF
C6
1000pF
IF-
R4
OPEN
L4
220nH
5
V
CC
LO
6
C27
0.1µF
C5
1000pF
J2
LO
R9
453Ω
J4
Figure 2. MAX2690 EV Kit Schematic (1.95GHz Operation)
_______________________________________________________________________________________
3
MAX2690 Evaluation Kit
Evaluates: MAX2690
_____________Layout Considerations
The MAX2690 EV kit can serve as a guide for your
board layout. To minimize the effects of parasitic ele-
ments (which can alter circuit performance), the ground
plane around and under the components that make
up the matching network (C1, C2, C3, and L2) and
inductor L1 (used for LGND) were removed. Keep PC
board trace lengths as short as possible to minimize
parasitic inductance. Also, keep decoupling capacitor
C5 as close to the MAX2690 as possible, with direct
connection to the ground plane. Keep traces away from
LGND and L1 to reduce stray capacitance and cou-
pling.
L1
39nH
L1
6.8nH
1
LGND
C3
1.2pF
RFIN
C2
0.5pF
NOTE: L2 REPLACED WITH SHORT.
C1
OPEN
1
LGND
C3
1000pF
RFIN
L2
22nH
C2
2.2pF
C1
OPEN
MAX2690
3
RFIN
MAX2690
3
RFIN
Figure 3. RFIN Match for 900MHz Operation
Figure 4. RFIN Match for 2.45GHz Operation
1.0"
Figure 5. MAX2690 EV Kit PC Board Layout—
Component Placement Guide
1.0"
Figure 6. MAX2690 EV Kit PC Board Layout—
Component Side
4
_______________________________________________________________________________________
MAX2690 Evaluation Kit
Evaluates: MAX2690
1.0"
Figure 7. MAX2690 EV Kit PC Board Layout—
Ground Plane
1.0"
Figure 8. MAX2690 EV Kit PC Board Layout—
Power Plane
1.0"
Figure 9. MAX2690 EV Kit PC Board Layout—Solder Side
_______________________________________________________________________________________
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