Texas Instruments VCA2614 Evaluation Module VCA2614EVM VCA2614EVM Datenbogen

2

SBOU015A

By using simple slide and DIP-switches, the VCA261xEVM
can be configured to accommodate several different modes
of operation. Before using the evaluation board, the user
should determine the configuration and required settings
needed for their specific evaluation. The demonstration board
comes from the factory with the following preset configura-
tion:

Slide Switches:

SW1, SW3, SW5, and SW7 are set to position 2.
SW2, SW4, SW6, and SW8 are set to position 1.

JP1 and JP2 have connections made at position B.

DIP-switch S1 has the following settings:

• MGS1 is set low
• MSG2 and MGS3 are set high
• VCAinSEL is set low
• FBSWcntl is set low

Components C20 and C29 are not populated.

The VCA261xEVM requires ±5V supplies (Connector J7) for
the output amplifiers (U1 and U3) and a separate +5V supply
(Connector J4) for the VCA261x. This configuration allows
for the monitoring of supply currents to the VCA261x inde-
pendently of the rest of the evaluation board. If monitoring of
the supplies is not required, a single +5V supply can be
substituted by connecting the two separate +5V supplies (J4
and J7) together. In this case the –5V supply is still required.

The input signals are applied to SMA connectors J3 and J6
for using the LNA and J2 and J8 for bypassing the LNA. The
input signals should be provided from low impedance source.
The inputs are ac-coupled into the LNA of the VCA261x
through 0.01µF capacitors and through transformers into the
VCA inputs.

The outputs of the evaluation board are located at SMA
connectors J1 and J9. When testing the EVM board, the
outputs J1 and J9 should be terminated into 50Ω loads such
as that of the inputs to a Spectrum Analyzer. This will result
in a 6dB loss of the signal magnitude. This loss should be
taken into account when taking all measurements.

By utilizing the switches provided at the inputs to amplifiers
U1 and U3, the outputs of the VCA261x can be monitored on
SMA connectors J1 and J9. Amplifiers U1 and U3 are
configured to have a gain of 1/2 in all modes except where
the signals are terminated to ground through a 500Ω equiva-
lent resistance. Table I shows the switch positions and the
resulting output.

U1

SW1

1

2

2

1

SW3

2

1

2

1

U3

SW2

1

2

2

1

SW4

2

1

2

1

NOTE: (1) Denotes Factory Preset.

TABLE I. Output Configuration.

000

–24dB to 0dB

24dB

0dB to 24dB

001

–27dB to 0dB

27dB

0dB to 27dB

010

–30dB to 0dB

30dB

0dB to 30dB

011

–33dB to 0dB

33dB

0dB to 33dB

100

–36dB to 0dB

36dB

0dB to 36dB

101

–39dB to 0dB

39dB

0dB to 39dB

110

–42dB to 0dB

42dB

0dB to 42dB

111

–45dB to 0dB

45dB

0dB to 45dB

TABLE II. MGS Settings.

The outputs of the VCA261x can be terminated through
500Ω on each output, and the output signals can then be
observed at test points TP1 and TP2 and test points TP3 and
TP4, respectively.

The five dip-switches (S1) control the gain range bits (MGS1,
MGS2, and MGS3) of the PGA, the input selection (VCA

IN

SEL) to select between input into the LNA or into the VCA,
and the feedback select switch to enable the switched-
feedback configuration. Table II shows the MGS settings and
the corresponding gain ranges.

There are two sets of solder switches (JP1 and JP2) that
enable setting the LNA gain. The following table outlines the
gain settings for the LNA and the corresponding switch
connections.