Detailed Description

The MAX2043 is a high-linearity up/downconverter inte-

grated with RF and LO baluns, an LO buffer, and an

SPDT LO input select switch. The EV kit circuit uses the

MAX2043 and consists mostly of supply-decoupling

capacitors, DC-blocking capacitors, a current-setting

resistor, and an IF balun. The MAX2043 EV kit circuit

allows for thorough analysis and a simple design-in.

Supply-Decoupling Capacitors

Capacitor C4 is a 22pF supply-decoupling capacitor

used to filter high-frequency noise. Capacitors C5, C7,

and C9 are larger 0.01µF used for filtering lower frequen-

cy noise on the supply.

DC-Blocking Capacitors

The MAX2043 has internal baluns at the RF and LO

inputs. These inputs have almost 0Ω resistance at DC,

and so DC-blocking capacitors C1, C6, and C8 are

used to prevent any external bias from being shunted

directly to ground.

LO Bias

Bias current for the integrated LO buffer is set with

resistor R1 (357Ω ±1%). The DC current of the device

can be reduced by increasing the value of R1 but the

device would operate at reduced performance levels

(see the

Modifying the EV Kit section).

Tap Network

Capacitor C3 helps to terminate the second-order inter-

modulation products.

IF±

The MAX2043 mixer has an IF frequency range of DC

to 350MHz. Note that these differential ports are ideal

for providing enhanced IIP2 performance. Single-

ended IF applications require a 1:1 balun to transform

the 50Ω differential output impedance to a 50Ω single-

ended output. After the balun, the IF return loss is bet-

ter than 15dB. The differential IF is used as an input

port for upconverter operation. The user can use a dif-

ferential IF amplifier following the mixer, but a DC block

is required on both IF pins. In this configuration, the IF+

and IF- pins need to be returned to ground through a

high resistance (about 1kΩ). This ground return can

also be accomplished by grounding the RF tap (pin 8)

and AC-coupling the IF+ and IF- ports (pins 13 and 14).

LOSEL

The EV kit includes a 47kΩ pullup resistor (R2) for easy

selection of the LO port. Providing a ground at TP3

selects LO2, and leaving TP3 open selects LO1. To

drive TP3 from an external source, follow the limits

called out in the MAX2043 device data sheet. Logic

voltages should not be applied to LOSEL without the

+5V supply voltage. Doing so can cause the on-chip

ESD diodes to conduct and could damage the device.

Layout Considerations

The MAX2043 evaluation board can be a guide for your

board layout. Pay close attention to thermal design

and close placement of components to the IC. The

MAX2043 package exposed paddle (EP) conducts

heat from the device and provides a low-impedance

electrical connection to the ground plane. The EP must

be attached to the PC board ground plane with a low

thermal and electrical impedance contact. Ideally, this

is achieved by soldering the backside of the package

directly to a top metal ground plane on the PC board.

Alternatively, the EP can be connected to an internal or

bottom-side ground plane using an array of plated vias

directly below the EP. The MAX2043 EV kit uses nine

evenly spaced 0.016in-diameter, plated through holes

to connect the EP to the lower ground planes.

Depending on the ground-plane spacing, large sur-

face-mount pads in the IF path may need to have the

ground plane relieved under them to reduce parasitic

shunt capacitance.

Modifying the EV Kit

The RF, LO, and IF ports are broadband matched, so

there is no need to modify the circuit for use anywhere

in the 1700MHz to 3000MHz RF range, 1900MHz to

3000MHz LO range, and 50MHz to 350MHz IF range.

The DC current of the device can be reduced if reduced

performance is acceptable. Reducing the current is

accomplished by increasing the value of R1. Doubling

the value of R1 reduces the DC current approximately

in half. Approximately 10% of the overall IC current is

used for basic operation of the device (R1 set at 357Ω)

and cannot be reduced.

MAX2043 Evaluation Kit

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