AD8317

Rev. 0 | Page 17 of 20

EVALUATION BOARD

Table 5. Evaluation Board (Rev. A) Configuration Options

Component

Function

Default Conditions

VPOS, GND

Supply and Ground Connections.

Not applicable

R1, C1, C2

Input Interface.

The 52.3

Ω resistor in position R1 combines with the AD8317's internal input

impedance to give a broadband input impedance of about 50

Ω. Capacitor

C1 and Capacitor C2 are dc-blocking capacitors. A reactive impedance

match can be implemented by replacing R1 with an inductor and C1 and C2

with appropriately valued capacitors.

R1 = 52.3

Ω (Size 0402)

C1 = 47 nF (Size 0402)

C2 = 47 nF (Size 0402)

R5, R7

Temperature Compensation Interface.

The internal temperature compensation network is optimized for input signals

up to 3.6 GHz when R7 is 10 k

Ω. This circuit can be adjusted to optimize

performance for other input frequencies by changing the value of the

R5 = 200

Ω (Size 0402)

R7 = open (Size 0402)

R2, R3, R4, R6, RL,

CL

Output Interface—Measurement Mode.

In measurement mode, a portion of the output voltage is fed back to Pin VSET

via R2. The magnitude of the slope of the VOUT output voltage response can

be used as a back-terminating resistor or as part of a single-pole, low-pass

filter.

R2 = 0

Ω (Size 0402)

R3 = open (Size 0402)

R4 = open (Size 0402)

R6 = 1 k

Ω (Size 0402)

RL = CL = open (Size 0402)

R2, R3

Output Interface—Controller Mode.

In this mode, R2 must be open. In controller mode, the AD8317 can control the

gain of an external component. A setpoint voltage is applied to Pin VSET, the

value of which corresponds to the desired RF input signal level applied to the

AD8317 RF input. A sample of the RF output signal from this variable-gain

component is selected, typically via a directional coupler, and applied to

AD8317 RF input. The voltage at Pin VOUT is applied to the gain control of

the variable gain element. A control voltage is applied to Pin VSET. The

magnitude of the control voltage can optionally be attenuated via the

voltage divider comprising R2 and R3, or a capacitor can be installed in

position R3 to form a low-pass filter along with R2.

R2 = open (Size 0402)

R3 = open (Size 0402)

C4, C5,

Power Supply Decoupling.

The nominal supply decoupling consists of a 100 pF filter capacitor placed

physically close to the AD8317 and a 0.1 μF capacitor placed nearer to the

power supply input pin.

C5 = 100 pF (Size 0402)

C4 = 0.1 μF (Size 0603)

C3

Filter Capacitor.

The low-pass corner frequency of the circuit that drives Pin VOUT can be

lowered by placing a capacitor between CLPF and ground. Increasing this

capacitor increases the overall rise/fall time of the AD8317 for pulsed input

signals. See the Output Filtering section for more details.

C3 = 8.2 pF (Size 0402)