AD8340
EVALUATION BOARD
The evaluation board circuit schematic for the AD8340 is
shown in Figure 39.
The evaluation board is configured to be driven from a
single-ended 50 Ω source. Although the input of the AD8340 is
differential, it may be driven single-ended, with no loss of
performance.
The low-pass corner frequency of the baseband I and Q chan-
nels can be reduced by installing capacitors in the C11 and C12
positions. The low-pass corner frequency for either channel is
approximated by
45 kHz × 10 nF
f3dB ≈ Cexternal + 0.5 pF
On this evaluation board, the I and Q baseband circuits are
identical to each other, so the following description applies
equally to each. The connections and circuit configuration for
the Q baseband inputs are described in Table 4.
The baseband input of the AD8340 requires a differential volt-
age drive. The evaluation board is set up to allow such a drive by
connecting the differential voltage source to QBBP and QBBM.
The common-mode voltage should be maintained at approxi-
mately 0.5 V. For this configuration, Jumpers W1 to W4 should
be removed.
The baseband input of the evaluation board may also be driven
with a single-ended voltage. In this case, a bias level is provided
to the unused input from Potentiometer R10 by installing either
W1 or W2.
Setting SW1 in Position B disables the AD8340 output amplifier.
With SW1 set to Position A, the output amplifier is enabled.
With SW1 set to Position A, an external voltage signal, such as a
pulse, can be applied to the DSOP SMA connector to exercise
the output amplifier enable/disable function.
Rev. 0 | Page 16 of 20