AD8341

Rev. 0 | Page 17 of 20

EVALUATION BOARD

The evaluation board circuit schematic for the AD8341 is

shown in Figure 41.

The evaluation board is configured to be driven from a

single-ended 50 Ω source. Although the input of the AD8341 is

differential, it may be driven single-ended, with no loss of per-

formance.

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

pF

0.5

nF

10

kHz

45

+

×

≈

FLT

C

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 AD8341 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 through 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 AD8341 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.

Table 4. Evaluation Board Configuration Options

Components

Function

Default Conditions

R7, R9, R11,

R14, R15, R19,

R20, R21, C15,

C19, W3, W4

I Channel Baseband Interface. Resistors R7 and R9 may be installed to accommodate a

baseband source that requires a specific terminating impedance. Capacitors C15 and C19

are bypass capacitors.

For single-ended baseband drive, the Potentiometer R11 can be used to provide a bias level

to the unused input (install either W3 or W4).

R7, R9 = Not Installed

R11 = Potentiometer, 2 kΩ,

10 Turn (Bourns)

R14 = 4 kΩ (Size 0603)

R15 = 44 kΩ (Size 0603)

R19, R20, R21 = 0 Ω

(Size 0603)

C15, C19 = 0.1 µF

(Size 0603)

W3 = Jumper (Installed)

W4 = Jumper (Open)

R1, R3, R10,

R12, R13, R16,

R17, R18, C16,

C20, W1, W2

Q Channel Baseband Interface. See the I Channel Baseband Interface section.

R1, R3 = Not Installed

R10 = Potentiometer, 2 kΩ,

10 Turn (Bourns)

R12 = 4 kΩ (Size 0603)

R13 = 44 kΩ (Size 0603)

R16, R17, R18 = 0 Ω

(Size 0603)

C16, C20 = 0.1 µF

(Size 0603)

W1 = Jumper (Installed)

W2 = Jumper (Open)

C11, C12

Baseband Low-Pass Filtering. By adding Capacitor C11 between QFLP and QFLM, and C12

between IFLP and IFLM, the 3 dB low-pass corner frequency of the baseband interface can

be reduced from 230 MHz (nominal). See equation in text.

C11, C12 = Not Installed

T1, C17, C18,

L1, L2

Output Interface. The 1:1 balun transformer, T1, converts the 50 Ω differential output to 50

Ω single-ended. C17 and C18 are dc blocks. L1 and L2 provide dc bias for the output.

C17, C18 = 100 pF

(Size 0603)

T1 = ETC1-1-13 (M/A-COM)

L1, L2 = 120 nH

(Size 0603)

L3, L4, C5, C6

Input Interface. The input impedance of the AD8341 requires 1.2 nH inductors in series

with RFIP and RFIM for optimum return loss when driven by a single-ended 50 Ω line. C5

and C6 are dc blocks.

L3, L4 = 1.2 nH (Size 0402)

C5, C6 = 100 pF (Size 0603)