ADPA1122

• Complete Bias Control and Sequencing Solution for Pulsed GaN Radar Power Amplifiers
• Pin Compatible with ADI's existing Pulser Board and with ADI's GaN Power Amplifier Evaluation Boards
• Operation in Drain Pulsed Mode or Gate Pulsed Mode
• Optional Crowbar Circuit for Fast Turn Off in Drain Pulsed Mode
• Single 24 V to 50 V Power Supply with on-board Negative Gate Voltage Generation.
• Drain Current Monitoring Circuit

Pulser Plus is a reference design for biasing Gallium Nitride RF Power Amplifiers. It plugs directly into Analog Devices’ GaN PA evaluation boards such as ADPA1106 and ADPA1107. The only input signals required to control and operate the board are a power supply voltage between 24 V and 50V and a 0V/3V signal on the Drain Pulse Enable or Gate Pulse Enable digital inputs.

Pulser Plus was specifically designed to enable fast pulsing of GaN Radar Power Amplifiers. It can support RF pulses as short as 1us and with rise and fall times of less than 100 ns in both Drain Pulsed mode and Gate Pulsed Mode.

• 2-layer Rogers 4350B evaluation board with heat spreader
• End launch 2.92 mm jack RF connectors
• Through calibration path (depopulated)
• Drain or gate pulsing capability

The ADPA1122-EVALZ consists of a 2-layer printed circuit board (PCB) fabricated from a 10 mil thick, Rogers 4350B copper clad mounted to an aluminum heat spreader. The heat spreader assists in providing thermal relief to the device as well as mechanical support to the PCB. Mounting holes on the heat spreader allow the spreader to be attached to a heat sink. Alternatively, the spreader can be clamped to a hot and cold plate. The RFIN and RFOUT ports on the ADPA1122-EVALZ are populated by 2.92 mm (K) female coaxial connectors. The ADPA1122-EVALZ is populated with components suitable for use over the entire operating temperature range of the device. To calibrate board trace losses, a through calibration path is provided between the J1 and J2 connectors. J1 and J2 must be populated with 2.92 mm (K) coaxial connectors to use the through calibration path.

Ground, power, and gate control are provided by two 24-pin headers (J3 and J4) on the ADPA1122-EVALZ. The pinouts for these two headers are shown in Table 1 in the user guide.

RF traces on the ADPA1122-EVALZ are 50 Ω, grounded, coplanar waveguide. The package ground leads and the exposed paddle connect directly to the ground plane. Multiple vias connect the top and bottom ground planes with particular focus on the area directly beneath the ground paddle to provide adequate electrical conduction and thermal conduction to the heat spreader.

The ADPA1122-EVALZ ships with a drain pulser board that assists with control and application of a pulsed drain bias. The ADPA1122-EVALZ also ships with an extender board that can interconnect the pulser board and evaluation board, providing a cutout to allow drain-current monitoring with a current probe. The extender board also allows the ADPA1122-EVALZ to be inserted into an oven without having to insert the pulser board.

For full details on the ADPA1122, see the ADPA1122 data sheet, which must be consulted in conjunction with the user guide when using the ADPA1122-EVALZ.