_________________________Quick Start

The MAX2450 EV kit is fully assembled and factory test-
ed. Follow the instructions in the

Connections and

Setup section.

Test Equipment Required

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

_______________General Description

The MAX2450 evaluation kit (EV kit) simplifies evalua-
tion 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

130MHz to 160MHz VCO (2x the IF frequency)

Single-Ended Modulator I and Q Inputs

Single-Ended 50

Modulator Output

Single-Ended 50

Demodulator Input

CMOS-Compatible Enable Input

Single-Ended or Differential Demodulator
I and Q Outputs

Fully Assembled and Tested

Evaluates: MAX2450/MAX2451/MAX2452

MAX2450 Evaluation Kit

PART

TEMP. RANGE

BOARD TYPE

MAX2450EVKIT-SO

0°C to +70°C

Surface Mount

QTY

DESCRIPTION

C1C6, C9,

C11, C12,

C15, C16

C7, C8

C13, C14

0.01µF ceramic capacitors
Vitramon VJ1206103MXX

C17, C18, C19

100nH, 10% inductor
CoilCraft 1008CS-101XKBC

L2, L3

Q_IN, I_IN,

IF_OUT, IF_IN

R1, R4

, 5% resistor

R3, R5

47k

, 5% resistors

potentiometer

R17

5.6k

, 5% resistor

10µF, 10V, 20% tantalum capacitors
Sprague 293D106X001B or
AVX TAJB106010

56pF, 5% ceramic capacitors
Vitramon VJ1206A330JXA

0.1µF, 10% ceramic capacitors
Vitramon VJ1206Y104MXX

SUPPLIER

PHONE

FAX

AVX
Coilcraft
M/A-COM
Sprague
Vishay/Vitramon

(803) 946-0690
(708) 639-6400
(617) 564-3100
(603) 224-1961
(203) 268-6261

(803) 626-3123
(708) 639-1469
(617) 564-3050
(603) 224-1430
(203) 452-5670

______________Component Suppliers

DESIGNATION

Not included. Use 1µH for additional
power-supply rejection, if needed.

BNC connectors

10k

, 5% resistors

____________________Component List

______________Ordering Information

R18

49.9

, 1% resistor

R19

200

, 5% resistor

R23, R24

100k

, 5% resistors

JU10

3-pin header

Varactor Diode
M/A-COM MA4ST080CK-287

Maxim MAX2450CWP

Maxim MAX436CSD

19-0454; Rev 1a; 3/96

________________________________________________________________

Maxim Integrated Products

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800

Evaluates: MAX2450/MAX2451/MAX2452

MAX2450 Evaluation Kit

_______________________________________________________________________________________

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 ter-

minals 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.

Modulator Setup

1) Connect a cable from the spectrum analyzer to the

IF_OUT BNC connector on the EV kit.

2) Set the spectrum analyzer's center frequency to

70MHz and its frequency span to 1MHz/div.

3) 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.

4) 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 (1mV

RMS

) at 70.1MHz.

4) Connect a cable from the signal generator to IF_IN

on the EV kit.

Analysis

1) Using the spectrum analyzer to observe the modu-

lator 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:

The 70MHz tone is the leakage from LO, with a mag-
nitude typically 36dB below the modulated output.
This is due to V

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 sup-
pression. 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 out-
put amplitudes are approximately 500mVp-p. Any
difference in the I and Q output amplitudes produces
the amplitude mismatch:

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 typi-
cal 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 V

through

a jumper. To test the power-down function, move the
JU10 shunt from the ENABLE to the ENABLE posi-
tion. This shorts the ENABLE pin to ground. The
supply current for the MAX2450 (+3V) should drop
below 2µA. (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 fre-
quency of the on-chip oscillator by varying the capaci-
tance of the parallel LC resonant network on the EV kit.
Use the following formula to determine the oscillation
frequency:

Vp - p = 2 2 x 50 x 10

dBm - 30

Amplitude Mismatch = 20 x log

f =

EQ EQ

where

where C

VAR

is the capacitance of each varactor diode.

This EV kit uses a common-cathode dual varactor
diode (D1) as a tuning element. Applying different volt-
ages 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 oscil-
lator 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 com-
pletely and shunt it directly on the PC board. The exter-
nal oscillator amplitude should be 200mVp-p.

ENABLE

Jumper JU10 controls the MAX2450 enable function.
Refer to Table 1 for jumper selection. To use an exter-
nal 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.

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 environ-
ment 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 net-
work 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.

Evaluates: MAX2450/MAX2451/MAX2452

MAX2450 Evaluation Kit

_______________________________________________________________________________________

Table 1. Jumper JU10 Functions

SHUNT LOCATION

ENABLE PIN

MAX2450

ENABLE

Connected to V

Enabled

ENABLE

Connected to GND

Disabled

= L1 + L

and

+ C

STRAY

VAR

STRAY

Evaluates: MAX2450/MAX2451/MAX2452

MAX2450 Evaluation Kit

_______________________________________________________________________________________

MAX2450

MAX436

1 FREQ_ADJ

+5V

V+

IF_OUT

GND

I_IN

Q_IN

PRE_OUT

LO_V

IF_IN

GND

I_OUT

Q_OUT

LO_GND

TANK

V+

IOUT

IN+

IF_OUT

IF_IN

BNC

V+

Z+

ISET

N.C.

V-

Z-

N.C.

IN-

V-

0.1

SHORT

100nH

0.1

CU1

BNC

I_N

Q_IN

PRE_OUT

JU10

TP2

TP3

TP4

0.1

R23

100k

R24

100k

R17
5.6k

I_OUT

GND

I_OUT

47k

10k

47k

R19

200

R18

49.9

C13

0.01

C16
0.1

JU1

+5V

+3V

+5V

GND

-5V

C17

10V

C18
10

10V

C19
10

10V

C12
0.1

C15

0.1

C14

0.01

0.1

C11

0.1

56pF

C6
0.1

56pF

R2
56

-5V

CU2

CU3

CU4

TP5

TP6

TP7

Q_OUT

GND

Q_OUT

+3V

TP1

SHORT

10k

Figure 1. MAX2450 EV Kit Schematic

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: MAX2450EVKIT

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: MAX2450EVKIT