Datasheet

Description

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1 Description

The Texas Instruments VCA8500BOARD evaluation module makes it easy to evaluate the performance of

the VCA8500 variable gain amplifier. The evaluation module operates in three modes: Default Power Up,

PC Control, and Direct Control. Default-Power-Up mode does not require any external clocking or data

input to enable the operation of the VCA8500. The functionality in Default-Power-Up mode is limited to

factory-programmed modes. PC-Control mode uses the included software to operate all of the functions of

the VCA8500. The software was written on Windows™ XP and its operation has been verified with

Windows™ XP. Direct-Control mode uses external control and data signals to control the functions of the

VCA8500.

The VCA8500BOARD has the following features:

• Easy testing of the VCA8500

• Single-ended input

• Three modes of operation:

– Default Power Up

– PC Control

– Direct Control

2 Initial Configuration

2.1 Power Supply

The VCA8500BOARD has provisions for six separate power supplies:

• +5 V: Positive VCA Supply

– This positive 5 V supplies the CW and VCA circuits. (P2)

• +3.3 V: Positive VCA Supply

– This positive 3.3 V supplies the LNA, Digital circuit and VCA Outputs . Ensure that all three pads of

W1 solder jumper are shorted. (P2)

• +5 V/–5 V: Supplies for all other circuitry

– These supply all other +5 V/-5 V requirements onboard. (P4)

• +15 V/–15 V: Supplies for CW Amplifiers

– These supplies are optional for the CW amplifiers only. The user does not need them connected

unless using CW Mode. To drive these amplifiers with +15 V/–15 V, W2 and W3 solder jumpers

should be open. (P3)

3 Signals

3.1 Input Signals

The input signals are applied to SMA connectors J1 to J8. The input impedance of the VCA is 8 kΩ. The

inputs are ac-coupled into the LNA of the VCA8500 through 1-μF capacitors and do not attenuate the

input signal.

3.2 Output Signals

The outputs of the evaluation module are located at SMA connectors J21 through J28 for the TGC

outputs, and J10 to J19 for the CW outputs. The outputs from the VCA8500 are buffered with operational

amplifiers.

Windows is a trademark of Microsoft Corporation.

VCA8500BOARD SLOU216B–January 2008–Revised January 2013

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