AD8318

Rev. B | Page 22 of 24

EVALUATION BOARD

Table 6. Evaluation Board (Rev. A) Bill of Materials

Component

Function

Default Conditions

VP, GND

Supply and Ground Connections

Not Applicable

SW1, R3

Device Enable. When in Position A, the ENBL pin is connected to VP and the

AD8318 is in operating mode. In Position B, the ENBL pin is grounded through

R3, putting the device in power-down mode. The ENBL pin may be exercised

by a pulse generator connected to ENBL SMA and SW1 in Position B.

SW1 = A

R3 = 10 kΩ (Size 0603)

R1, C1, C2

Input Interface. The 52.3 Ω resistor (R1) combines with the AD8318 internal

input impedance to give a broadband input impedance of 50 Ω. C1 and 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 = 1 nF (Size 0402)

C2 = 1 nF (Size 0402)

R2

Temperature Sensor Interface. The temperature sensor output voltage is

available at the SMA labeled TEMP via the current limiting resistor, R2.

R2 = 1 kΩ (Size 0402)

R4

Temperature Compensation Interface. The internal temperature compensation

resistor is optimized for an input signal of 2.2 GHz when R4 is 500 Ω. This circuit

can be adjusted to optimize performance for other input frequencies by

changing the value of Resistor R4. See the Temperature Compensation of

Output Voltage section.

R4 = 499 Ω (Size 0603)

R7, R8, R9, R10

Output Interface—Measurement Mode. In measurement mode, a portion of

the output voltage is fed back to the VSET pin via R7. The magnitude of the

to VSET. R10 can be used as a back-terminating resistor or as part of a single-

pole, low-pass filter.

R7 = 0 Ω = (Size 0402)

R8 = open (Size 0402)

R9 = open (Size 0402

R10 = 0 Ω (Size 0402)

R7, R8, R9, R10

Output Interface—Controller Mode. In this mode, R7 must be open. In

controller mode, the AD8318 can control the gain of an external component. A

setpoint voltage is applied to the VSET pin, the value of which corresponds to

the desired RF input signal level applied to the AD8318 RF input. The

magnitude of the control voltage is optionally attenuated via the voltage

divider comprised of R8 and R9, or a capacitor can be installed in R8 to form a

low-pass filter along with R9. See the Controller Mode section for more details.

R7 = open (Size 0402)

R8 = open (Size 0402)

R9 = 0 Ω (Size 0402)

R10 = 0 Ω (Size 0402)

C5, C6, C7, C8, R5, R6

Power Supply Decoupling. The nominal supply decoupling consists of a 100 pF

filter capacitor placed physically close to the AD8318, a 0 Ω series resistor, and

a 0.1 μF capacitor placed closer to the power supply input pin.

C5 = 0.1 μF (Size 0603)

C6 = 100 pF (Size 0402)

C7 = 100 pF (Size 0402)

C8 = 0.1 μF (Size 0603)

R5 = 0 Ω (Size 0603)

R6 = 0 Ω (Size 0603)

C9

Loop Filter Capacitor. The low-pass corner frequency of the circuit that drives

the VOUT pin can be lowered by placing a capacitor between CLPF and

ground. Increasing this capacitor increases the overall rise/fall time of the

AD8318 for pulsed input signals. See the Output Filtering section for more details.

C9 = open (Size 0603)