Rainbow Electronics MAX2055 User Manual

General Description

The MAX2055 high-performance, digitally controlled,
variable-gain, differential analog-to-digital converter
(ADC) driver/amplifier (DVGA) is designed for use from
30MHz to 300MHz in base station receivers.

The device integrates a digitally controlled attenuator
and a high-linearity single-ended-to-differential output
amplifier, which can either eliminate an external trans­former, or can improve the even-order distortion perfor­mance of a transformer-coupled circuit, thus relaxing
the requirements of the anti-alias filter preceding an
ADC. Targeted for ADC driver applications to adjust
gain either dynamically or as a one-time channel gain
setting, the MAX2055 is ideal for applications requiring
high performance. The attenuator provides 23dB of
attenuation range with ±0.2dB accuracy.

The MAX2055 is available in a thermally enhanced 20­pin TSSOP-EP package and operates over the -40°C to
+85°C temperature range.

Applications

Cellular Base Stations

PHS/PAS Infrastructure

Receiver Gain Control

Broadband Systems

Automatic Test Equipment

Terrestrial Links

High-Performance ADC Drivers

Features

♦ 30MHz to 300MHz Frequency Range

♦ Single-Ended-to-Differential Conversion

♦ -3dB to +20dB Variable Gain

♦ 40dBm Output IP3 (at All Gain States and 70MHz)

♦ 2nd Harmonic -76dBc

♦ 3rd Harmonic -69dBc

♦ Noise Figure: 5.8dB at Maximum Gain

♦ Digitally Controlled Gain with 1dB Resolution and

±0.2dB Accuracy

♦ Adjustable Bias Current

MAX2055

Digitally Controlled, Variable-Gain, Differential

ADC Driver/Amplifier

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

20

19

18

17

16

15

14

13

1

2

3

4

5

6

7

8

GND

ATTN

OUT

GND

I

SET

B4

GND

RF_IN

V

CC

C

C

AMP

IN

L

E

C

BP

B0

B1

B2

B3

12

11

9

10

I

BIAS

RF_OUT+

RF_OUT-

ATTENUATION

LOGIC

CONTROL

V

CC

TSSOP

MAX2055

TOP VIEW

19-2799; Rev 0; 4/03

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.

*EP = Exposed paddle.

Pin Configuration/

Functional Diagram

PART TEMP RANGE PIN-PACKAGE

MAX2055EUP-T -40°C to +85°C 20 TSSOP-EP*

MAX2055

Digitally Controlled, Variable-Gain, Differential
ADC Driver/Amplifier

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

DC ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1; VCC= +4.75V to +5.25V, GND = 0V. No input signals applied, and input and output ports are terminated with
50Ω. R1 = 1.13kΩ, T

A

= -40°C to +85°C. Typical values are at VCC= +5V and TA= +25°C, unless otherwise noted.) (Notes 1, 2)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

All Pins to GND. .....................................-0.3V to +(VCC+ 0.25V)

Input Signal (RF_IN)............................…………………….20dBm

Output Power (RF_OUT) ...................................................24dBm

Continuous Power Dissipation (T

A

= +70°C)

20-Pin TSSOP (derate 21.7mW/°C above +70°C) ...........2.1W

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +165°C

Lead Temperature (soldering, 10s) .................................+300°C

AC ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1; VCC= +4.75V to +5.25V, GND = 0V, max gain (B0 = B1 = B2 = B3 = B4 = 0), R1= 1.13kΩ, P

OUT

= 5dBm,

f

IN

= 70MHz, 50Ω system impedance. Typical values are at VCC= +5V and TA= +25°C, unless otherwise noted.) (Notes 1, 2)

SUPPLY

Supply Voltage V

Supply Current I

I

SET

CONTROL INPUTS

Control Bits Parallel 5 Bits

Input Logic High 2V

Input Logic Low 0.6 V

Input Leakage Current -1.2 +1.2 µA

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Current I

CC

CC

SET

4.75 5.0 5.25 V

240 290 mA

1.1 mA

Frequency Range f

Gain G 19.9 dB

Amplitude Unbalance (Note 3) 0.06 dB

Phase Unbalance (Note 3) 0.7 D eg r ees

Minimum Reverse Isolation 29 dB

Noise Figure NF 5.8 dB

Output 1dB Compression Point P

2nd-Order Output Intercept Point OIP2

3rd-Order Output Intercept Point OIP3 All gain conditions, 5dBm/tone at RF_OUT 40 dBm

2nd Harmonic 2f

3rd Harmonic 3f

RF Gain-Control Range 23 dB

Gain-Control Resolution 1dB

Attenuation Absolute Accuracy Compared to the ideal expected attenuation ±0.2 dB

Attenuation Relative Accuracy Between adjacent states

Gain Drift Over Temperature TA = -40°C to +85°C ±0.3 dB

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

R

1dB

IN

IN

f

+ f2, f1 = 70MHz, f2 = 71MHz, 5dBm/tone

1

at RF_OUT

30 300 MHz

25.7 dBm

75 dBm

-76 dBc

-69 dBc

+0.05/

-0.2

dB

MAX2055

Digitally Controlled, Variable-Gain, Differential

ADC Driver/Amplifier

_______________________________________________________________________________________ 3

Note 1: Guaranteed by design and characterization.
Note 2: All limits reflect losses of external components. Output measurements are taken at RF_OUT using the application circuit

shown in Figure 1.

Note 3: The amplitude and phase unbalance are tested with 50Ω resistors connected from OUT+/OUT- to GND.

AC ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1; VCC= +4.75V to +5.25V, GND = 0V, max gain (B0 = B1 = B2 = B3 = B4 = 0), R1= 1.13kΩ, P

OUT

= 5dBm,

f

IN

= 70MHz, 50Ω system impedance. Typical values are at VCC= +5V and TA= +25°C, unless otherwise noted.) (Notes 1, 2)

Typical Operating Characteristics

(Circuit of Figure 1, VCC= 5.0V, R1= 1.13kΩ, max gain (B0 = B1 = B2 = B3 = B4 = 0), P

OUT

= 5dBm, TA= +25°C, unless other-

wise noted.)

SUPPLY CURRENT vs. TEMPERATURE

MAX2055 toc01

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

603510-15

220

230

240

250

260

270

210

-40 85

VCC = 5.25V

VCC = 5.0V

VCC = 4.75V

INPUT RETURN LOSS vs. RF FREQUENCY

(ALL STATES)

MAX2055 toc02

FREQUENCY (MHz)

INPUT RETURN LOSS (dB)

27024060 90 120 180150 210

35

30

25

20

15

10

5

0

40

30 300

OUTPUT RETURN LOSS vs. RF FREQUENCY

(ALL STATES)

MAX2055 toc03

FREQUENCY (MHz)

OUTPUT RETURN LOSS (dB)

27024060 90 120 180150 210

35

30

25

20

15

10

5

0

40

30 300

GAIN vs. RF FREQUENCY (ALL STATES)

MAX2055 toc04

FREQUENCY (MHz)

GAIN (dB)

27024060 90 120 180150 210

-5

0

5

10

15

20

25

-10
30 300

GAIN vs. RF FREQUENCY

MAX2055 toc05

FREQUENCY (MHz)

GAIN (dB)

27024060 90 120 180150 210

12

14

16

18

20

22

24

10

30 300

TA = +85°C

TA = +25°C

TA = -40°C

GAIN vs. RF FREQUENCY

MAX2055 toc06

FREQUENCY (MHz)

GAIN (dB)

27024060 90 120 180150 210

12

14

16

18

20

22

24

10

30 300

VCC = 5.25V

VCC = 5.0V

VCC = 4.75V

Gain Flatness Over 50MHz
Bandwidth

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Peak-to-peak for all settings 0.5 dB

Attenuator Switching Time 50% control to 90% RF 40 ns

Input Return Loss fR = 30MHz to 300MHz, all gain conditions 15 dB

Output Return Loss

fR = 30MHz to 250MHz, all gain conditions 15

= 250MHz to 300MHz, all gain conditions 12

f

R

dB

MAX2055

Digitally Controlled, Variable-Gain, Differential
ADC Driver/Amplifier

4 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Circuit of Figure 1, VCC= 5.0V, R1= 1.13kΩ, max gain (B0 = B1 = B2 = B3 = B4 = 0), P

OUT

= 5dBm, TA= +25°C, unless other-

wise noted.)

ATTENUATION ABSOLUTE ACCURACY

(ALL STATES)

1.0

0.8

0.6

0.4

0.2

0

-0.2

-0.4

ABSOLUTE ACCURACY (dB)

-0.6

-0.8

-1.0
30 300

FREQUENCY (MHz)

MAX2055 toc07

27024060 90 120 180150 210

ATTENUATION RELATIVE ACCURACY

(ALL STATES)

1.0

0.8

0.6

0.4

0.2

0

-0.2

-0.4

RELATIVE ACCURACY (dB)

-0.6

-0.8

-1.0
30 300

FREQUENCY (MHz)

27024060 90 120 180150 210

MAX2055 toc08

REVERSE ISOLATION vs. RF FREQUENCY

40

36

32

28

REVERSE ISOLATION (dB)

24

20

30 300

FREQUENCY (MHz)

MAX2055 toc09

27024060 90 120 180150 210

NOISE FIGURE vs. FREQUENCY

8.0

7.5

7.0

6.5

6.0

5.5

NOISE FIGURE (dB)

5.0

4.5

4.0

TA = +85°C

TA = -40°C

30 300

FREQUENCY (MHz)

OUTPUT IP3 vs. FREQUENCY

44

42

40

38

TA = +85°C

36

OIP3 (dBm)

34

32

30

30 300

TA = +25°C

P

= P

RF1

AT OUTPUT, ∆f = 1MHz

FREQUENCY (MHz)

TA = +25°C

TA = -40°C

= 5dBm

RF2

OUTPUT P-1dB vs. FREQUENCY

27

26

MAX2055 toc10

25

24

23

OUTPUT P-1dB (dBm)

22

27024060 90 120 180150 210

21

30 300

TA = +85°C

TA = -40°C

FREQUENCY (MHz)

TA = +25°C

MAX2055 toc11

OUTPUT P-1dB (dBm)

27024060 90 120 180150 210

OUTPUT IP3 vs. FREQUENCY

44

42

MAX2055 toc13

40

38

36

OIP3 (dBm)

34

32

27024060 90 120 180150 210

30

VCC = +5.25V

VCC = +5V

VCC = +4.75V

P

= P

= 5dBm

RF1

RF2

AT OUTPUT, ∆f = 1MHz

30 300

FREQUENCY (MHz)

27024060 90 120 180150 210

MAX2055 toc14

IIP3 (dBm)

OUTPUT P-1dB vs. FREQUENCY

27

26

25

24

VCC = +5V

23

22

21

30 300

VCC = +5.25V

VCC = +4.75V

FREQUENCY (MHz)

MAX2055 toc12

27024060 90 120 180150 210

INPUT IP3 vs. ATTENUATION STATE

55

50

45

40

35

30

25

20

15

024

P

= P

RF1

AT OUTPUT, ∆f = 1MHz,

= 70MHz

f

IN

ATTENUATION STATE

RF2

= 5dBm

MAX2055 toc15

20164 8 12

MAX2055

Digitally Controlled, Variable-Gain, Differential

ADC Driver/Amplifier

_______________________________________________________________________________________ 5

Typical Operating Characteristics (continued)

(Circuit of Figure 1, VCC= 5.0V, R1= 1.13kΩ, max gain (B0 = B1 = B2 = B3 = B4 = 0), P

OUT

= 5dBm, TA= +25°C, unless other-

wise noted.)

HARMONIC (dBc)

HARMONIC (dBc)

3RD HARMONIC vs. FREQUENCY

-55

-60

-65

-70

TA = +85°C

-75

-80

-85
30 300

TA = +25°C

FREQUENCY (MHz)

TA = -40°C

2ND HARMONIC vs. FREQUENCY

-60

-65

VCC = +5.25V

-70

-75

-80

VCC = +5V

-85

-90
30 300

VCC = +4.75V

FREQUENCY (MHz)

3RD HARMONIC vs. FREQUENCY

-55

-60

MAX2055 toc16

-65

-70

VCC = +4.75V

HARMONIC (dBc)

-75

-80

27024060 90 120 180150 210

-85
30 300

VCC = +5V

FREQUENCY (MHz)

VCC = +5.25V

MAX2055 toc17

27024060 90 120 180150 210

OUTPUT IP2 vs. FREQUENCY (f1 + f2)

85

80

MAX2055 toc19

75

70

65

OIP2 (dBm)

60

55

27024060 90 120 180150 210

50

TA = -40°C

30 300

TA = +25°C

P

= P

RF1

AT OUTPUT, ∆f = 1MHz

FREQUENCY (MHz)

TA = +85°C

= 5dBm

RF2

MAX2055 toc20

27024060 90 120 180150 210

2ND HARMONIC vs. FREQUENCY

-60

TA = -40°C

-65

-70

-75

HARMONIC (dBc)

-80

-85

-90
30 300

TA = +85°C

FREQUENCY (MHz)

OUTPUT IP2 vs. FREQUENCY (f1 + f2)

85

80

75

70

65

OIP2 (dBm)

60

55

50

30 300

VCC = +5.0

VCC = +5.25V

FREQUENCY (MHz)

VCC = +4.75V

P

= P

RF1

RF2

AT OUTPUT, ∆f = 1MHz

MAX2055 toc18

TA = +25°C

27024060 90 120 180150 210

MAX2055 toc21

= 5dBm

27024060 90 120 180150 210

OUTPUT-PORT AMPLITUDE UNBALANCE

vs. FREQUENCY

0.25

0.20

0.15

0.10

AMPLITUDE UNBALANCE (dB)

0.05

0

30 300

FREQUENCY (MHz)

MAX2055 toc22

27024060 90 120 180150 210

OUTPUT-PORT PHASE UNBALANCE

vs. FREQUENCY

3.0

2.5

2.0

1.5

1.0

PHASE UNBALANCE (DEGREES)

0.5

0

30 300

FREQUENCY (MHz)

MAX2055 toc23

27024060 90 120 180150 210

SUPPLY CURRENT vs. TEMPERATURE

MAX2055 toc24

TEMPERATURE (°C)

SUPPLY CURRENT (mA)

603510-15

220

230

240

250

260

270

210

-40 85

VCC = 5.25V

VCC = 5.0V

VCC = 4.75V

INPUT RETURN LOSS vs. RF FREQUENCY

(ALL STATES)

MAX2055 toc25

FREQUENCY (MHz)

INPUT RETURN LOSS (dB)

27024060 90 120 180150 210

50

40

30

20

10

0

60

30 300

OUTPUT RETURN LOSS vs. FREQUENCY

(ALL STATES)

MAX2055 toc26

FREQUENCY (MHz)

OUTPUT RETURN LOSS (dB)

27024060 90 120 180150 210

50

40

30

20

10

0

60

30 300

GAIN vs. RF FREQUENCY (ALL STATES)

MAX2055 toc27

FREQUENCY (MHz)

GAIN (dB)

27024060 90 120 180150 210

-5

0

5

10

15

20

25

-10
30 300

GAIN vs. RF FREQUENCY

MAX2055 toc28

FREQUENCY (MHz)

GAIN (dB)

27024060 90 120 180150 210

12

14

16

18

20

22

24

10

30 300

TA = +85°C

TA = +25°C

TA = -40°C

GAIN vs. RF FREQUENCY

MAX2055 toc29

FREQUENCY (MHz)

GAIN (dB)

27024060 90 120 180150 210

12

14

16

18

20

22

24

10

30 300

VCC = 5.25V

VCC = 5.0V

VCC = 4.75V

ATTENUATION ABSOLUTE ACCURACY

(ALL STATES)

MAX2055 toc30

FREQUENCY (MHz)

ABSOLUTE ACCURACY (dB)

27024060 90 120 180150 210

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1.0

-1.0
30 300

ATTENUATION RELATIVE ACCURACY

(ALL STATES)

MAX2055 toc31

FREQUENCY (MHz)

RELATIVE ACCURACY (dB)

27024060 90 120 180150 210

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1.0

-1.0
30 300

REVERSE ISOLATION vs. RF FREQUENCY

MAX2055 toc32

FREQUENCY (MHz)

REVERSE ISOLATION (dB)

27024060 90 120 180150 210

24

28

32

36

40

20

30 300

MAX2055

Digitally Controlled, Variable-Gain, Differential
ADC Driver/Amplifier

6 _______________________________________________________________________________________

Typical Operating Characteristics

(Circuit of Figure 2, VCC= 5.0V, R1= 909Ω, max gain, (B0 = B1 = B2 = B3 = B4 = 0), P

OUT

= 5dBm, TA= +25°C, unless otherwise

noted.)

MAX2055

Digitally Controlled, Variable-Gain, Differential

ADC Driver/Amplifier

_______________________________________________________________________________________ 7

Typical Operating Characteristics (continued)

(Circuit of Figure 2, VCC= 5.0V, R1= 909Ω, max gain, (B0 = B1 = B2 = B3 = B4 = 0), P

OUT

= 5dBm, TA= +25°C, unless otherwise

noted.)

NOISE FIGURE vs. FREQUENCY

MAX2055 toc33

FREQUENCY (MHz)

NOISE FIGURE (dB)

27024060 90 120 180150 210

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

4.0
30 300

TA = +85°C

TA = -40°C

TA = +25°C

OUTPUT P-1dB vs. FREQUENCY

MAX2055 toc34

FREQUENCY (MHz)

OUTPUT P-1dB (dBm)

27024060 90 120 180150 210

22

23

24

25

26

27

21

30 300

TA = +85°C

TA = -40°C

T

A

= +25°C

OUTPUT P-1dB vs. FREQUENCY

MAX2055 toc35

FREQUENCY (MHz)

OUTPUT P-1dB (dBm)

27024060 90 120 180150 210

22

23

24

25

26

27

21

30 300

VCC = +4.75V

VCC = +5V

VCC = +5.25V

OUTPUT IP3 vs. FREQUENCY

MAX2055 toc36

FREQUENCY (MHz)

OIP3 (dBm)

27024060 90 120 180150 210

32

34

36

38

42

40

44

30

30 300

TA = +85°C

TA = -40°C

TA = +25°C

P

RF1

= P

RF2

= 5dBm

AT OUTPUT, ∆f = 1MHz

OUTPUT IP3 vs. FREQUENCY

MAX2055 toc37

FREQUENCY (MHz)

OIP3 (dBm)

27024060 90 120 180150 210

32

34

36

38

42

40

44

30

30 300

VCC = +5.25V

VCC = +4.75V

VCC = +5V

P

RF1

= P

RF2

= 5dBm

AT OUTPUT, ∆f = 1MHz

INPUT IP3 vs. ATTENUATION STATE

MAX2055 toc38

ATTENUATION STATE

IIP3 (dBm)

20164 8 12

20

25

30

35

40

45

50

55

15

024

P

RF1

= P

RF2

= 5dBm
AT OUTPUT, ∆f = 1MHz,
f

IN

= 70MHz

3RD HARMONIC vs. FREQUENCY

MAX2055 toc39

FREQUENCY (MHz)

HARMONIC (dBc)

27024060 90 120 180150 210

-80

-75

-70

-65

-60

-55

-85
30 300

TA = +85°C

TA = -40°C

TA = +25°C

3RD HARMONIC vs. FREQUENCY

MAX2055 toc40

FREQUENCY (MHz)

HARMONIC (dBc)

27024060 90 120 180150 210

-80

-75

-70

-65

-60

-55

-85
30 300

VCC = +4.75V

VCC = +5V

VCC = +5.25V

2ND HARMONIC vs. FREQUENCY

MAX2055 toc41

FREQUENCY (MHz)

HARMONIC (dBc)

27024060 90 120 180150 210

-80

-75

-70

-65

-60

-55

-50

-85

-90
30 300

TA = +85°C

TA = -40°C

TA = +25°C

MAX2055

Digitally Controlled, Variable-Gain, Differential
ADC Driver/Amplifier

8 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(Circuit of Figure 2, VCC= 5.0V, R1= 909Ω, max gain, (B0 = B1 = B2 = B3 = B4 = 0), P

OUT

= 5dBm, TA= +25°C, unless otherwise

noted.)

HARMONIC (dBc)

2ND HARMONIC vs. FREQUENCY

-50

-55

-60

VCC = +5V

VCC = +5.25V

VCC = +4.75V

FREQUENCY (MHz)

-65

-70

-75

-80

-85

-90
30 300

OUTPUT IP2 vs. FREQUENCY (f1 + f2)

85

TA = -40°C

FREQUENCY (MHz)

TA = +85°C

TA = +25°C

P

RF1

AT OUTPUT, ∆f = 1MHz

= P

RF2

= 5dBm

80

MAX2055 toc42

75

70

65

OIP2 (dBm)

60

55

27024060 90 120 180150 210

50

30 300

27024060 90 120 180150 210

OUTPUT IP2 vs. FREQUENCY (f1 + f2)

80

75

MAX2055 toc43

70

65

OIP2 (dBm)

60

55

50

VCC = +5.0V

VCC = +5.25V

P

RF1

AT OUTPUT, ∆f = 1MHz

30 300

FREQUENCY (MHz)

VCC = +4.75V

= P

RF2

MAX2055 toc44

= 5dBm

27024060 90 120 180150 210

OUTPUT-PORT AMPLITUDE UNBALANCE

vs. FREQUENCY

0.25

0.20

0.15

0.10

AMPLITUDE UNBALANCE (dB)

0.05

0

30 300

FREQUENCY (MHz)

OUTPUT-PORT PHASE UNBALANCE

vs. FREQUENCY

3.0

MAX2055 toc45

27024060 90 120 180150 210

2.5

2.0

1.5

1.0

PHASE UNBALANCE (DEGREES)

0.5

0

30 300

FREQUENCY (MHz)

MAX2055 toc46

27024060 90 120 180150 210

MAX2055

Digitally Controlled, Variable-Gain, Differential

ADC Driver/Amplifier

_______________________________________________________________________________________ 9

Pin Description

Table 1. Suggested Components of
Circuit of Figure 1

Table 2. Suggested Components of
Circuit of Figure 2

PIN NAME FUNCTION

1, 9 V

2 RF_IN

3, 18, 20, EP GND

4–8B4–B0 Attenuation Control Bits. Digital input for attenuation control. See Table 3 for attenuation setting.

10 RF_OUT-

11 RF_OUT+

12 I

13 C

14 L

15 AMP

16 C

17 I

19 ATTN

CC

BIAS

BP

E

C

SET

Power Supply. Bypass to GND with capacitors as close to the pin as possible as shown in the typical
application circuits (Figures 1 and 2).

Signal Input. Internally matched to 50Ω over the operating frequency. See the typical application
circuit for recommended component values.

Ground. Use low-inductance layout techniques on the PC board. Solder the exposed paddle to the
board ground plane.

Inverted Differential Signal Output. Requires an external pullup choke inductor (120mA typical
current) to V

Noninverted Differential Signal Output. Requires an external pullup choke inductor (120mA typical
current) to V

Amplifier Bias Input. See Figures 1 and 2 for detailed connection.

Bypass Capacitor. See Figures 1 and 2 for detailed connection.

Amplifier DC Ground. Requires choke inductor that can handle supply current. DC resistance of
inductor should be less than 0.2Ω.

Amplifier Input. Requires DC-coupling to allow biasing.

IN

Compensation Capacitor. Requires connection to AMPIN (pin 15) for stability.

Connect R1 from I

Attenuator Output. Requires external DC-blocking capacitor.

OUT

along with a DC-blocking capacitor; see Figures 1 and 2.

CC

along with a DC-blocking capacitor; see Figures 1 and 2.

CC

to GND (see Table 1 or Table 2 for values).

SET

C1, C3–C6, C8, C9, C10, C12 1nF 0603

C2, C11 100pF 0603

L1, L3 330nH 0603

L2 100nH 0603

L4, L5 680nH 1008

R1 1.13kΩ 0603

R7 10Ω 0603

T1, T2 1:1 —

COMPONENT VALUE SIZE

C1, C3, C4, C5, C7–C10, C12 1nF 0603

C2, C11 100pF 0603

L1, L2, L3 330nH 0603

L4, L5 680nH 1008

R1 909Ω 0603

R7 10Ω 0603

T2 1:1 —

COMPONENT VALUE SIZE

MAX2055

Detailed Description

The MAX2055 is a high-dynamic-range, digitally con­trolled, variable-gain differential ADC driver/amplifier
(DVGA) for use in applications from 30MHz to 300MHz.
The amplifier is designed for 50Ω single-ended input
and 50Ω differential output systems.

The MAX2055 integrates a digital attenuator with a
23dB selectable attenuation range and a high-linearity,
single-ended-to-differential output amplifier. The attenu­ator is digitally controlled through five logic lines:
B0–B4. The on-chip attenuator provides up to 23dB of
attenuation with ±0.2dB accuracy. The single-ended
input to differential output amplifier utilizes negative

feedback to achieve high gain and linearity over a wide
bandwidth.

Applications Information

Digitally Controlled Attenuator

The digital attenuator is controlled through five logic
lines: B0, B1, B2, B3, and B4. Table 3 lists the attenua­tion settings. The input and output of this attenuator
require external DC blocking capacitors. The attenua­tor’s insertion loss is approximately 2dB, when the con­trol bits are set to 0dB (B0 = B1 = B2 = B3 = B4 = 0).

Single-Ended-to-Differential Amplifier

The MAX2055 integrates a single-ended-to-differential
amplifier with a nominal gain of 22dB in a negative

Digitally Controlled, Variable-Gain, Differential
ADC Driver/Amplifier

10 ______________________________________________________________________________________

Figure 1. Typical Application Circuit

V

CC

C

C

3

CONTROL

INPUTS

V

CC

2

1

V

CC

RF_IN

RF_IN

C

1

R

7

C

C

12

11

2

3

GND

4

B4

5

B3

B2

B1

B0

V

CC

RF_OUT-

ATTENUATION

LOGIC

CONTROL

MAX2055

L

5

1

V

CC

C

10

6

7

8

9

10

C

8

GND

ATTN

GND

AMP

I

RF_OUT+

L

4

OUT

I

C

BIAS

20

19

18

SET

17

16

C

C

15

IN

14

L

E

13

BP

12

11

R

1

L

2

L

3

C

9

C4

C

5

C

6

T

1

1

L

1

T

2

RF_OUT

feedback topology. This amplifier is optimized for a fre­quency range of operation from 30MHz to 300MHz with
a high-output third-order intercept point (OIP3). The
bias current is chosen to optimize the IP3 of the amplifi­er. When R1is 1.13kΩ (909Ω if using the circuit of
Figure 2), the current consumption is 240mA while
exhibiting a 40dBm typical output IP3 at 70MHz. The
common-mode inductor, L2, provides a high common­mode rejection with excellent amplitude and phase bal­ance at the output. L2must handle the supply current
and have DC resistance less than 0.2Ω.

Choke Inductor

The single-ended amplifier input and differential output
ports require external choke inductors. At the input,
connect a 330nH bias inductor from AMPIN(pin 15) to
I

BIAS

(pin 12). Connect 680nH choke inductors from
RF_OUT+ (pin 11) and RF_OUT- (pin 10) to VCC. These
connections provide bias current to the amplifier.

Layout Considerations

A properly designed PC board is an essential part of
any RF/microwave circuit. Keep RF signal lines as short
as possible to reduce losses, radiation, and induc­tance. For best performance, route the ground-pin
traces directly to the exposed pad underneath the

MAX2055

Digitally Controlled, Variable-Gain, Differential

ADC Driver/Amplifier

______________________________________________________________________________________ 11

Figure 2. Low-Cost Application Circuit

CONTROL

INPUTS

V

CC

C

C

3

2

1

V

CC

RF_IN

RF_IN

C

1

R

V

CC

7

C

C

12

11

2

3

GND

4

B4

5

B3

B2

B1

B0

V

CC

RF_OUT-

ATTENUATION

LOGIC

CONTROL

MAX2055

L

5

1

V

CC

C

10

6

7

8

9

10

C

8

GND

ATTN

GND

AMP

I

RF_OUT+

L

4

OUT

I

C

BIAS

20

19

18

SET

17

16

C

C

15

IN

14

L

E

13

BP

12

11

R

1

L

2

C

7

L

3

C

9

C

4

C

5

L

1

T

2

RF_OUT

MAX2055

package. This pad should be connected to the ground
plane of the board by using multiple vias under the
device to provide the best RF/thermal conduction path.
Solder the exposed pad on the bottom of the device
package to a PC board exposed pad.

The MAX2055 Evaluation Kit can be used as a refer­ence for board layout. Gerber files are available upon
request at www.maxim-ic.com.

Power-Supply Bypassing

Proper voltage-supply bypassing is essential for high­frequency circuit stability. Bypass each VCCpin with a
1000pF and 100pF capacitor. Connect the 100pF
capacitor as close to the device as possible. Resistor
R7 helps reduce switching transients. If switching tran­sients are not a concern, R7 is not required. Therefore,
connect pin 9 directly to VCC.

Exposed Paddle RF Thermal

Considerations

The EP of the MAX2055’s 20-pin TSSOP-EP package
provides a low thermal-resistance path to the die. It is
important that the PC board on which the IC is mounted
be designed to conduct heat from this contact. In addi­tion, the EP provides a low-inductance RF ground path
for the device.

It is recommended that the EP be soldered to a ground
plane on the PC board, either directly or through an
array of plated via holes.

Soldering the pad to ground is also critical for efficient
heat transfer. Use a solid ground plane wherever
possible.

Digitally Controlled, Variable-Gain, Differential
ADC Driver/Amplifier

12 ______________________________________________________________________________________

Table 3. Attenuation Setting vs. Gain­Control Bits

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

Chip Information

TRANSISTOR COUNT: 325

PROCESS: BiCMOS

ATTENUATION B4 B3* B2 B1 B0

0 00000

1 00001

2 00010

3 00011

4 00100

5 00101

6 00110

7 00111

8 01000

9 01001

10 01010

11 01011

12 01100

13 01101

14 01110

15 01111

16 1 X 0 0 0

17 1 X 0 0 1

18 1 X 0 1 0

19 1 X 0 1 1

20 1 X 1 0 0

21 1 X 1 0 1

22 1 X 1 1 0

23 1 X 1 1 1

MAX2055

Digitally Controlled, Variable-Gain, Differential

ADC Driver/Amplifier

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.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13

© 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages

.)

TSSOP4.40mm.EPS