MAXIM MAX2055 User Manual

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General Description

The MAX2055 evaluation kit (EV kit) simplifies the evalu­ation of the MAX2055 high-linearity, digitally controlled,
variable-gain analog-to-digital converter (ADC)
driver/amplifier (DVGA). The EV kit is fully assembled
and tested at the factory. Standard 50Ω SMA connec­tors are included on the EV kit for the input and output
to allow quick and easy evaluation on the test bench.

This data sheet provides a list of equipment required to
evaluate the device, a straightforward test procedure to
verify functionality, a circuit schematic for the kit, a bill
of materials (BOM) for the kit, and artwork for each
layer of the PC board.

Features

♦ Fully Assembled and Tested

♦ 30MHz to 300MHz Frequency Range

♦ -3dB to +20dB Variable Gain

♦ Output IP3: 40dBm (All Gain Settings at 70MHz)

♦ -76dBc 2nd Harmonic

♦ -69dBc 3rd Harmonic

♦ Noise Figure: 5.8dB at Maximum Gain

♦ Digitally Controlled Gain with 1dB Resolution and

±0.2dB Accuracy

♦ Adjustable Bias Currents

Evaluates: MAX2055

MAX2055 Evaluation Kit

________________________________________________________________ Maxim Integrated Products 1

19-2888; Rev 0; 5/03

Component List

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Ordering Information

*EP = Exposed paddle.

Component Suppliers

Note: When contacting these component suppliers, please
specify you are using the MAX2055.

SUPPLIER PHONE WEBSITE

Coilcraft 847-639-6400 www.coilcraft.com

Johnson 507-833-8822 www.johnsoncomponents.com

Murata 770-436-1300 www.murata.com

TOKO 800-745-8656 www.tokoam.com

PART TEMP RANGE IC PACKAGE

MAX2055EVKIT -40°C to +85°C 20 TSSOP-EP*

DESIGNATION QTY DESCRIPTION

C1, C3–C6, C8,

C9, C10, C12

C2, C11 2

C7 1 Not used

R1 1 1.13kΩ ±1% resistor (0603)

R2–R6 5 47kΩ ±5% resistors (0603)

R7 1 10Ω ±5% resistor (0603)

L1, L3 2

L2 1

1000pF ±5%, 50V C0G ceramic

9

capacitors (0603)
Murata GRM1885C1H102J

100pF ±5%, 50V C0G ceramic
capacitors (0603)
Murata GRM1885C1H101J

330nH ±5%, wire-wound inductors
(0603)
Coilcraft 0603LS-331XJBC

100nH ±5%, wire-wound inductor
(0603)
Coilcraft 0603LS-101XJBC

DESIGNATION QTY DESCRIPTION

L4, L5 2

J1, J2 2

J3 1

J4, J5, J6 0 Not installed

T1, T2 2 MiniCircuit TC1-50-4 transformers

U1 1 MAX2055EUP-T

680nH ±5%, wire-wound inductors
(1008)
Coilcraft 1008CS-681XJBC or
TOKO FSLM2520-R68J

PC board edge-mount SMA RF
connectors
(flat-tab launch)
Johnson 142-0741-856

Header 5 x 2 (0.100 spacing for

0.062in thick board)
Molex 10-88-1101 or equivalent

Evaluates: MAX2055

MAX2055 Evaluation Kit

2 _______________________________________________________________________________________

Quick Start

The MAX2055 EV kit is fully assembled and factory test­ed. Follow the instructions in the Connections and
Setup section for proper device evaluation. Table 1 lists
the attenuation setting vs. gain-control bit.

Test Equipment Required

• DC supply capable of delivering 5.25V and 400mA
of continuous current

• HP 8648 (or equivalent) signal source

• HP 8561E (or equivalent) spectrum analyzer capa-

ble of covering the MAX2055’s frequency range, as
well as a few harmonics

• Two digital multimeters (DMMs) to monitor VCCand
ICC, if desired

• HP 8753D (or equivalent) network analyzer to mea­sure return loss and gain

• Filters to attenuate harmonic output of signal sources,
if harmonic measurements are desired

Connections and Setup

This section provides a step-by-step guide to testing
the basic functionality of the EV kit. As a general pre­caution to prevent damaging the outputs by driving
high-VSWR loads, do not turn on DC power or RF
signal generators until all connections are made.

Gain Setting

Connect the header pins for B4–B0 to GND for maxi­mum gain (20dB typ). See Table 1 for other gain­setting configurations. To set a logic high on B4–B0,
leave the respective header pin unconnected as on­board resistors pull up the logic to +5V. To control
B4–B0 using external logic (voltage limits per the data
sheet), ensure that +5V is applied to the chip. Failure
to do so can cause the on-chip ESD diodes to draw
significant current and can damage the part.

Testing the Supply Current

1) Connect 50Ω terminations to RF_IN and RF_OUT.

2) With the DC supply disabled, set it to +5.0V (through
a low internal resistance ammeter, if desired) and
connect to the +5V and GND terminals on the EV kit.
If available, set the current limit to 400mA.

3) Enable the DC supply; the supply current should
read approximately 250mA.

Testing the Power Gain

1) Connect the RF signal generator to the RF_IN SMA
connector. Do not turn on the generator’s output. Set

the generator to an output frequency of 70MHz, and
set the generator power level to -15dBm.

2) Connect the spectrum analyzer to the RF_OUT SMA
connector. Set the spectrum analyzer to a center fre­quency of 70MHz and a total span of 1MHz.

3) With the DC supply disabled, set it to +5.0V (through
a low internal-resistance ammeter, if desired) and
connect to the +5V and GND terminals on the EV kit.
If available, set the current limit to 400mA.

4) Connect B4–B0 to GND for 0dB attenuation.

5) Enable the DC supply, and then activate the RF gen­erator’s output. A 70MHz signal shown on the spec-

Table 1. Attenuation Setting vs. Gain­Control Bits

*Enabling B4 disables B3 and the minimum attenuation is
16dB.

ATTENUATION

(dB)

0 00000

1 00001

2 00010

3 00011

4 00100

5 00101

6 00110

7 00111

8 01000

9 01001

10 0 1 0 1 0

11 0 1 0 1 1

12 0 1 1 0 0

13 0 1 1 0 1

14 0 1 1 1 0

15 0 1 1 1 1

16 1X 000

17 1X 001

18 1X 010

19 1X 011

20 1X 100

21 1X 101

22 1X 110

23 1X 111

B4

(16dB)

B3*

(8dB)B2(4dB)B1(2dB)B0(1dB)

trum analyzer display should indicate a magnitude
of approximately 5dBm. Be sure to account for
external cable losses.

6) (Optional) Gain can be determined with a network
analyzer. This has the advantage of displaying gain
over a swept frequency band, in addition to display­ing input and output return loss. Refer to the network
analyzer manufacturer’s user manual for setup
details.

Detailed Description

Figure 1 shows the schematic for the MAX2055 EV kit.
The EV kit is matched for operation up to 300MHz.
Capacitors C1, C4, C5, C8, and C9 are DC-blocking
capacitors for the RF_IN, ATTN

OUT

, and RF_OUT ports.
To reduce the possibility of noise pickup, capacitors
C2, C3, C10, C11, and C12 form the VCCdecoupling
network. Inductors L1–L5 provide a method of biasing.
Inductor L2 needs to handle the total IC current and
have a DC resistance that is less than 0.2Ω. If the DC
resistance is higher than 0.2Ω, the value of R1 may
need to be adjusted down to maintain the nominal
operating current. Inductors L4 and L5 are nonmagnet­ic coils that provide the output supply bias for the
amplifier. Transformer T1 is used to convert the single­ended attenuator output to a differential signal. This
technique results in an improved 2nd harmonic perfor­mance for the device. The amplifier can be driven single
ended if the improved 2nd harmonic is not required
(see Modifying the EV Kit section). Output transformer
T2 enables single-ended measurements, in addition to
providing common-mode rejection for the 2nd harmon­ic. Resistor R7 helps reduce video leakage during
switching. Replace R7 with a 0Ω resistor if video leak­age is not a concern.

Modifying the EV Kit

The EV kit is easily configured for other topologies.

For a single-ended amplifier input:

1) Remove T1 and place a low-inductance short circuit
between the T1 surface-mount pads that connect
capacitors C4 to C5.

2) Add a 1000pF 0603 case style capacitor for C7.

3) Change L2 to the same style and value inductor as
L1 (330nH) noted in the Component List.

4) Change R1 to 909Ω (to adjust the DC current to
compensate for the higher L2 resistance).

Note: In this configuration, C6 is not required.

The EV kit also provides the ability for additional methods
of testing by adding in the option for an interstage RF
connection along with differential RF output connections.

Layout Considerations

The MAX2055 evaluation boards can be used as a guide
for your board layout. Give close attention to thermal
design and close placement of parts to the IC. The
MAX2055 package exposed paddle (EP) conducts heat
out of the part and provides a low-impedance electrical
connection. The EP must be attached to the PC board
ground plane with a low thermal and electrical-imped­ance contact. Ideally, this is provided by soldering the
backside package contact directly to a top metal ground
plane on the PC board. Alternatively, the EP can be con­nected to a ground plane using an array of plated vias
directly below the EP. The MAX2055 EV kit uses eight
evenly spaced, 0.016in-diameter, plated through holes to
connect the EP to the lower ground planes.

Depending on the RF ground plane spacing, large sur­face-mount pads in the RF path may need to have the
ground plane relieved under them to reduce shunt
capacitance.

Evaluates: MAX2055

MAX2055 Evaluation Kit

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