feature

Crossover; High Frequency Operation: 4GHz to 18GHz Integrated RF Decoupling Capacitors Low Power; Active Mode: 30mA; Power Down Mode: 17mA; Low Phase Noise: –147 dBc/Hz; Single DC Supply: 3.3 V, ADF4xxx compatible with PLL; temperature range: -40°C to +105°C; small package: 3 mm x 3 mm LFCSP.

application

Frequency range extenders; point-to-point radios; VSAT radios; communications test equipment.

General Instructions

The ADF5000 prescaler is a low noise, low power, fixed RF divider block that can be used to divide frequencies up to 18GHz to lower frequencies suitable for input to PLL ICs such as the ADF4156 or ADF4106. The ADF5000 provides a divide-by-2 function. The ADF5000 is powered by a 3.3V supply and has a differential 100Ω RF output, allowing direct interface to the differential RF input of PLLs such as the ADF4156 and ADF4106.

Absolute Maximum Ratings

Stresses above the Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device under the conditions described in the operating section of this specification or any other conditions above is not implied. Long-term exposure to absolute maximum rating conditions may affect device reliability.

The device is a high-performance RF integrated circuit with an ESD rating of 2kv, Human Body Model (HBM), and is ESD sensitive. Take proper handling and assembly precautions.

Typical performance characteristics

Evaluation Board Printed Circuit Board

The evaluation board has four connectors, as shown in Figure 8. The RF input connector (J4) is a high-frequency precision shape memory alloy connector produced by Emerson. The connector is mechanically compatible with SMA, 3.5 mm and 2.92 mm cables.

The evaluation board is powered by a 3.0V to 3.6V power supply, which should be connected to the J1 SMA connector. Power can also be connected using the T3 (VDDx) and T2 (GND) test points.

Differential RF outputs are output via J2 and J3 SMA connectors. If only one of the outputs is used, the unused output should be properly terminated with 50Ω SMA termination.

The Chip Enable (CE) pin can be controlled using the T1 test point. If this function is not required, the test point can be left unconnected.

Bill of Materials

PCB material buildup

The evaluation board is made of Rogers RO4003C material (0.008 inches). The RF track width is 0.015 inches for a controlled 50Ω characteristic impedance. The complete printed circuit board (PCB) stack is shown in Figure 9.

Application circuit

The ADF5000 can be single-ended or different from any analog device—the PLL family of integrated circuits. Differential connections are recommended for best performance and maximum power transfer. The application circuit shown in Figure 10 shows the ADF5000 used as an RF prescaler in a microwave 12GHz PLL loop. The ADF5000 decomposes the 12GHz RF signal to 6GHz and feeds it differentially into the ADF4156 phase-locked loop. An active filter topology using the OP184 op amp is used to provide the wide tuning range typically required for microwave VCOs.

The positive input pin of the OP184 is biased towards half of the ADF4156 charge pump supply (VP). This can be easily achieved using a simple resistor divider, ensuring adequate decoupling close to the + in one of the OP184's pins. This configuration, in turn, allows the use of a single positive supply for the op amp. Alternatively, to optimize performance by ensuring a clean bias voltage, a low noise regulator such as the ADP150 can be used to directly power a resistor divider network or + in a pin.

Dimensions