MAX2056 查看數據表（PDF） - Maxim Integrated

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MAX2056

800MHz to 1000MHz Variable-Gain Amplifier with Analog Gain Control

Maxim Integrated 

800MHz to 1000MHz Variable-Gain

Amplifier with Analog Gain Control

Table 1. Typical Application Circuit

Components Values

DESIGNATION

C1, C3, C5, C10

C2, C4, C6, C8, C9

C7

C13, C14, C15

R1

R2

VALUE

47pF

1000pF

3.9pF

0.1µF

1.2kΩ

3.92kΩ

TYPE

Microwave capacitors (0402)

Microwave capacitors (0402)

Microwave capacitor (0402)

Microwave capacitors (0603)

±1% resistor (0402)

±1% resistor (0402)

Applications Information

Analog Attenuation Control

A single input voltage at the VCNTL pin adjusts the gain

of the MAX2056. Up to 22dB of gain-control range is

provided through a single attenuator. At the maximum

gain setting, each attenuator’s insertion loss is approxi-

mately 1.7dB. With the single attenuator at the maxi-

mum gain setting, the device provides a nominal

15.5dB of cascaded gain and 4.5dB of cascaded noise

figure.

If a larger gain-control range is desired, a second on-

chip attenuator can be connected in the signal path to

provide an additional 22dB of gain-control range. With

the second attenuator connected at the maximum gain

setting, the device typically exhibits 13.8dB of cascad-

ed gain. Note that the VCNTL pin simultaneously adjusts

both on-chip attenuators. The VCNTL input voltage dri-

ves a high-impedance load (>250kΩ). It is suggested

that a current-limiting resistor be included in series with

this connection to limit the input current to less than

40mA should the control voltage be applied when VCC

is not present. A series resistor of greater than 200Ω

will provide complete protection for 5V control voltage

ranges. Limit VCNTL input voltages to a 1.0V to 4.5V

range when VCC is present to ensure the reliability

of the device.

Amplifier Bias Current

The MAX2056 integrates a two-stage amplifier to simul-

taneously provide high gain and high IP3. Optimal per-

formance is obtained when R1 and R2 are equal to

1.2kΩ and 3.92kΩ, respectively. The typical supply cur-

rent is 136mA and the typical output IP3 is 39dBm

under these conditions.

Increasing R1 and R2 from the nominal values of 1.2kΩ

and 3.92kΩ reduces the bias current of each amplifier

stage, which reduces the total power consumption and

IP3 of the device. This feature can be utilized to further

decrease power consumption for applications that do

not require high IP3.

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 induc-

tance. For best performance, route the ground-pin

traces directly to the exposed pad underneath the

package. This pad MUST be connected to the ground

plane of the board by using multiple vias under the

device to provide the best RF and thermal conduction

path. Solder the exposed pad on the bottom of the

device package to a PC board exposed pad.

Power-Supply Bypassing

Proper voltage-supply bypassing is essential for high-

frequency circuit stability. Bypass each VCC pin with

capacitors placed as close to the device as possible.

Place the smallest capacitor closest to the device. Refer

to the MAX2056 evaluation kit data sheet for more details.

Exposed Paddle RF and Thermal

Considerations

The EP of the MAX2056’s 36-pin thin QFN-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 addi-

tion, the EP provides a low-inductance RF ground path

for the device.

The EP MUST 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 wher-

ever possible.

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