Datasheet

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1 Description
2 Power Supply Requirements
2.1 Voltage Limits Warning
3 Input Signals
4 VCA Control Voltage (V
CNTL
)
5 Output Configuration
Description
The VCA2617EVM is designed to provide ease of use in evaluating the performance of the VCA2617
variable gain amplifier. By using the 0 Ω jumpers and DIP-switches, the VCA2617EVM can be configured
to accommodate several different modes of operation. Before starting the evaluation, it is recommended to
review the state of each of the switches to verify the desired configuration.
The VCA2617EVM requires a +5V DUT supply (at connector JP1) for the VCA2617, and separate ± 5V
supplies (at connector JP2) for the output amplifiers (U1 and U2). This configuration allows for the
monitoring of supply currents to the VCA2617 independent of the rest of the evaluation board. If
monitoring the supplies is not required, a single +5V supply can be substituted for the two separate +5V
supplies. In this case, the –5V supply is still required. Please note that the pull-up resistors R17, R18 and
R19 are connected to the +5V supply, which is required to operate the VCA2617.
CAUTION
Exceeding the maximum input voltages can damage EVM components.
Undervoltage conditions may cause improper operation of some or all of
the EVM components.
The default configuration of the EVM is for the differential input configuration of the VCA2617. Here, a
single-ended input signal may be applied to SMA connectors J3 (PIN_A) and J4 (PIN_B). The transformer
will convert the signal into a differential signal and drive the VCA. Alternatively, each of the VCA2617
inputs can also be driven in single-ended configuration. To do so, use the appropriate solder switches
(SJPn) for the desired configuration. Please note that the VCA2617 inputs are internally biased and
therefore must be ac-coupled.
While the VCA2617 allows controlling both channels independently, the default configuration of the EVM
has both V
CNTL
pins tied together. An external control voltage can be applied at connector JP1 (pin 1). In
order to change to independent control, simply reconfigure the solder switches SJP9 and SJP10. Access
to the V
CNTL
pins is then provided through SMA connectors J9 and J10. This signal can be a dc voltage or
a customer-specific waveform. The typical range for the control voltage, as specified in the VCA2617
datasheet , is from 0.2V to 2.3V.
The differential outputs of the VCA2617 are fed into an amplifier stage set with a gain of 0.5V/V. Using the
0 Ω jumpers, this stage can be configured in two different ways:
• as a single-ended inverter (R23, R24—closed, R22, R25—open), or
• as a difference amplifier (R22, R25—closed, R23, R24—open; this is the default configuration).
After the amplifier stage, the signal outputs are provided at SMA connectors J5 (OUT_A) and J6 (OUT_B).
The differential outputs of the VCA2617 can be terminated with 500 Ω on each output, and the output
signals can then be checked at test points TP1 and TP2 and test points TP3 and TP4, respectively.
2 VCA2617EVM User's Guide SBOU033 – November 2005