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19-1350 Rev 2; 2/99
MAX2424/MAX2426 Evaluation Kits
________________General Description
The MAX2424/MAX2426 evaluation kits (EV kits) simplify evaluation of the MAX2424/MAX2426 900MHz imagereject transceiver. The EV kits provide 50 SMA connectors for all RF inputs and outputs. A varactor-based tank circuit is provided for the MAX2424/MAX2426 VCO and can be tuned by a potentiometer or external voltage. The VCO can be overdriven by an external source, if desired. (See external LO input under Adjustments and Control section). Switches are provided to control power-management features.
____________________________Features
o 50 SMA Ports for Testing Transmit and Receive Paths o SMA Port for Prescaler Output o Switches Included to Control Power-Management Features o VCO Frequency and Receiver Adjustable via On-Board Potentiometers or External Inputs o Fully Assembled and Tested
Evaluate: MAX2424/MAX2426
_______________Ordering Information
PART MAX2424EVKIT MAX2426EVKIT TEMP. RANGE -40C to +85C -40C to +85C IC PACKAGE 28 SSOP 28 SSOP
______________________________________________________________Component List
DESIGNATION QTY C1, C4, C5, C7, C9, C10, C12, 14 C15, C19, C22-C24, C28, C32 C2, C3 2 DESCRIPTION DESIGNATION QTY DESCRIPTION 6.8nH, 5% inductor (MAX2424) Coilcraft 0805HS-060TJBC 3.3nH, 5% inductor (MAX2426) Coilcraft 0805HS-030TJBC 100nH inductor Coilcraft 0805CS-101XKBC Not installed 12nH inductor Coilcraft 0805CS-120XMBC 18nH inductor Coilcraft 0805CS-180XMBC 82nH inductor Coilcraft 0805CS-820XKBC 10k potentiometers 1k, 5% resistors 10, 5% resistors (0402) (MAX2424) 20, 5% resistors (0402) (MAX2426) 47k, 5% resistor 10k, 5% resistors Not installed 10k, 5% resistors 301, 1% resistor 49.9, 1% resistors 0 resistor
47pF ceramic capacitors
L3
1
3.3pF ceramic capacitors (0603) (MAX2424) 8.0pF ceramic capacitors (0603) (MAX2426) 0.1F ceramic capacitors 0.01F ceramic capacitors 1000pF ceramic capacitor 10F, 10%, 10V tantalum capacitors AVX TAJB106K010 or Sprague 2930106X90010B 2.0pF ceramic capacitor (0603) (MAX2424) 4.0pF ceramic capacitor (0603) (MAX2426) Not installed Dual-varactor diode Alpha SMV1299-004 22nH inductor Coilcraft 0805CS-220XMBC 8.2nH inductor Coilcraft 0805CS-080XMBC MAX2426
L4 L5, L7 L6 L8 L9 R2, R3 R4, R5 R6, R7 R8 R9, R14-R17 R11, R21 R10, R13 R12 R18, R20 R19
1 0 1 1 1 2 2 2 1 5 2 2 1 2 1
C6, C14 C8, C11, C13, C29, C30, C31 C16 C17, C18
2 6 1 2
C26
1
C27, C33 D1 L1 L2
0 1 7 1
Component List continues on next page. 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 1-800-835-8769.
MAX2424/MAX2426 Evaluation Kits Evaluate: MAX2424/MAX2426
_______Component List (continued)
DESIGNATION QTY JU2, JU4, JU7, JU8 LNAGAIN, VCOADJ JU2, JU4, JU7, JU8, GND, VEXT, BPSK, DGND RXIN, RXOUT, TXOUT, TXIN, PREOUT, EXT LO INPUT SW1 U1 4 2 Shunts 1-pin headers DESCRIPTION
Connections and Signal Conditions
1) Verify that all shunts are installed across jumpers JU2, JU4, JU7, and JU8. 2) Verify that switch positions 1 through 5 on SW1 are set at the "logic 0" position. 3) Set a power supply to 3.3V and set the current limit to 100mA. 4) Connect the power supply to the VEXT and GND terminals on the EV kit. 5) Set a power supply to 2.3V and set the current limit to 100mA. 6) Connect the power supply to the BPSK and GND terminals on the EV kit. 7) For testing the receive path, set the signal source frequency to 915MHz (RF) and the power level to -35dBm. For testing the transmit path, set the signal source frequency to 1MHz and the signal level to 250mVp-p. Note that TXIN is terminated with a 50 load.
7
2-pin headers
6
SMA connectors (PC edge mount)
1 1
5-position dip switch MAX2424EAI 28-pin SSOP MAX2426EAI 28-pin SSOP
______________Component Suppliers
SUPPLIER* Alpha Industries AVX Coilcraft Sprague PHONE (617) 935-5150 (803) 946-0690 (847) 639-6400 (603) 224-1961 FAX (617) 933-2359 (803) 626-3123 (847) 639-1469 (603) 224-1430
Analysis
1) Turn on the on-chip oscillator by setting switch VCOON to "logic 1." To observe the VCO frequency, set switch DIV 1 to "logic 1" (disabling the prescaler and enabling the buffer amplifier) and connect an SMA cable from the spectrum analyzer to the PREOUT port. Set the VCO frequency to 925.7MHz by adjusting VCOADJ (R3). 2) The receive conversion gain can be evaluated by setting switch RXON to "logic 1," applying a 915MHz signal to the RXIN port, and observing the RXOUT port at 10.7MHz with the spectrum analyzer. The gain of the LNA in the receiver path can be adjusted by varying R2. Note: R12 and R18 are used as a resistive matching network to present an optimum 330 impedance to the RXOUT pin. This network results in a 14.2dB loss in the receiver path. Therefore, 14.2dB must be added to the power level observed on the spectrum analyzer to obtain the true receive output power. For example, with LNAGAIN set at VCC and the receive input level set at -35dBm, the receive output observed on the spectrum analyzer is approximately -27.2dBm. The true receive conversion gain is -27.2 - (-35) + 14.2 = 22dB. If desired, pads for C8, R18, C30, R12, L5, and C20 can be used to build a custom reactivematching network.
*Please indicate that you are using the MAX2424/MAX2426 when contacting these suppliers.
_________________________Quick Start
The MAX2424/MAX2426 EV kits are fully assembled and factory tested. Do not turn on the DC power and signal sources until all connections are made. The following discussion is based on the MAX2424 with a receive IF frequency of 10.7MHz, high-side LO injection and 1MHz transmit input with a 915MHz LO frequency. * RF-signal generator capable of generating frequencies up to 1GHz * Spectrum analyzer with frequency range at least to 3GHz, such as the HP8561 * Two power supplies capable of up to +5.5V output at 100mA
Test Equipment Required
2
_______________________________________________________________________________________
MAX2424/MAX2426 Evaluation Kits
3) Receive image rejection can be evaluated by changing the receive input frequency to 936.4MHz (while keeping the LO at 925.7MHz) and comparing the output signal level against the one measured in step 2. 4) Before evaluating the transmitter, ensure that the receiver is disabled by setting switch RXON to "logic 0." Set the VCO frequency to 915MHz by adjusting VCOADJ (R3). The transmit output power can be evaluated by setting switch TXON to "logic 1," applying a 1MHz signal at 250mVp-p to the TXIN port, and observing the TXOUT spectrum at 914MHz and 916MHz with a spectrum analyzer.
EXT LO Input
An external LO input may be applied by making the following board changes: Remove R6, R7, L3, L4, C2, C3, and C26. Add two 47pF in place of C27 and C33. Add three 49.9 (0402) resistors in place of R6, R7, and R21. Add three shorts in place of R11, L3, and L4. Apply the LO signal at 0dBm to EXTLO INPUT.
Evaluate: MAX2424/MAX2426
Layout Considerations
The MAX2424/MAX2426 EV boards can serve as a guide for your board layout. Take care in laying out the oscillator tank circuit. Oscillation frequency is sensitive to parasitic PC board capacitance, trace inductance, and package inductance. Keep the tank layout as symmetrical, tightly packed, and close to the device as possible to minimize LO feedthrough. When using a PC board with a ground plane, a cutout in the ground plane below the oscillator tank reduces parasitic capacitance. Also, keep traces carrying the receive and transmit signals as short as possible to minimize radiation and insertion loss due to the PC board.
Adjustments and Control
VCOADJ The VCO frequency can be tuned by adjusting onboard potentiometer R3. It can also be tuned by first removing the shunt from jumper JU7 and then applying an external voltage via the VCOADJ terminal. The supply providing the external voltage must be properly bypassed to minimize noise added to the LO. LNAGAIN The LNA gain can be adjusted using on-board potentiometer R2. LNA gain control can also be accomplished by first removing the shunt from jumper JU2 and then applying an external voltage via the LNA GAIN terminal. RXON and TXON The receive and transmit sections are enabled by setting switches RXON and TXON to "logic 1," respectively. Interference will result if both sections are active at the same time. When testing either the receive or transmit section, always disable the other section. To disable all chip functions, set all switches to "logic 0." To obtain an accurate reading of the device shutdown current, remove the shunt from JU4 and move the VCC connection from the VEXT terminal to the left side of JU4. Prescaler Control The function of PREOUT is controlled by the switches labeled "DIV1" and "64" (Table 1).
Table 1. PREOUT Function Control Switches
PREOUT FUNCTION LO buffered output Prescaler, /64 Prescaler, /65 SWITCH "SW1" POSITIONS DIV1 Logic 1 Logic 0 Logic 0 64 Don't care Logic 1 Logic 0
_______________________________________________________________________________________
3
MAX2424/MAX2426 Evaluation Kits Evaluate: MAX2424/MAX2426
VCC C6 0.1F 1 2 C28 47pF RXOUT SMA J1 C8 0.01F R12 301 C30 0.01F C14 0.1F 3 L5 OPEN C20 OPEN 4 C4 47pF L2 8.2nH GND TANK 24 R21 OPEN RXIN R6 C33 OPEN C3 R4 1k VCC CAP1 GND GND GND RXOUT TANK 25 28 VCC2 27 26 EXTLO INPUT SMA J13 C27 OPEN R11 OPEN C7 47pF L4 100nH R7 C2 D1 L3 C26 R5 1k R8 47k L9 82nH VCO ADJ JU7 C1 47pF VEXT C19 47F C2, C3 (pF) MAX2424 MAX2426 3.3 8.0 C26 (pF) 2.0 4.0 L3 nH 6.8 3.3 R6, R7 () 10 20
R18 49.9
R3 10k
RXIN SMA
J2
5
U1
L6 12nH
MAX2424 MAX2426
6 VCC GND GND TXOUT
VCC
23 C32 47pF
VCC2
VCC VCC C5 47pF C10 J5 47pF L8 18nH VEXT R2 10k JU2 C24 47pF LNA GAIN L1 22nH C15 47pF
7 8
VCC
22 C12 47pF 21 C16 1000pF C31 0.01F
VCC2
J4
PREOUT
PREOUT SMA
TXOUT SMA
9
PREGND 10 LNAGAIN
20
JU6
19 MOD 11 VEXT VCC DIV1 12 TXIN VCOON 18 R14 10k 17 R15 10k 13 TXIN RXON 16 R16 10k 14 CAP2 TXON 15 R17 10k TXON 5 6 RXON 4 7 VCOON 3 8 DIV1 2 9 R9 10k 64 1 10
VCC R19 C11 0 0.01F C29 0.01F C9 47pF
65
TXIN SMA
J3
64/65
R20 49.9
L7 OPEN C25 OPEN
R13 10k BPSK
R10 10k
OFF
SW1
OFF
C22 47pF VCC2
C13 0.01F
OFF
JU5 VEXT C18 10F 6.3V GND JU8 DGND JU4 C17 10F 6.3V VCC C23 47pF
Figure 1. MAX2424/MAX2426 EV Kits Schematic
4 _______________________________________________________________________________________
MAX2424/MAX2426 Evaluation Kits Evaluate: MAX2424/MAX2426
1.0"
1.0"
Figure 2. MAX2424/MAX2426 EV Kits Component Placement Guide--Component Side
Figure 3. MAX2424/MAX2426 EV Kits PC Board Layout-- Component Side
1.0"
1.0"
Figure 4. MAX2424/MAX2426 EV Kits PC Board Layout-- Ground Plane
Figure 5. MAX2424/MAX2426 EV Kits PC Board Layout-- Power Plane
5
_______________________________________________________________________________________
MAX2424/MAX2426 Evaluation Kits Evaluate: MAX2424/MAX2426
1.0"
1.0"
Figure 6. MAX2424/MAX2426 EV Kits PC Board Layout-- Solder Side
Figure 7. MAX2424/MAX2426 EV Kits 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.
6 _____________________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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