This version is outdated by a newer approved version.DiffThis version (12 Feb 2024 02:03) was approved by Joyce Velasco.

This is an old revision of the document!

AD-PAARRAY3552R-SL Hardware User Guide


The AD-PAARRAY3552R-SL is designed in a small form factor to manage the power sequencing of an RF transmitter signal chain, and is engineered to facilitate power sequencing for a two-stage Doherty amplifier (LDMOS + GaN) along with a one-stage Doherty amplifier (GaN only). However, users have the freedom to employ any GaN amplifiers of their choice.

The design incorporates the AD3552R dual-channel, 16-bit DAC which allows an ultrafast sub-µs voltage settling time of GaN gates from pinch-off to the normal operating voltage.

This also includes a high-side NMOS static switch driver, LTC7000, which adeptly handles key fault events such as overvoltage, overcurrent, and overtemperature.

The on-board MAX32666 ultralow power Arm Cortex®-M4 microcontroller exposes all the necessary debug and programming features to enable a complete software development experience with the system. The system's firmware is based on ADI's open-source no-OS framework and a user-friendly graphical user interface (GUI) for evaluation and further development.

The system can be powered from an external +38 V to +55 V supply, making it suitable for applications requiring high current capabilities.

Board Specifications

  • Dimension:
    • Length: 4 inch (101.6 mm)
    • Width: 2.7 inch (68.58 mm)
    • Thickness: 0.062 inch (1.62 mm)
  • PCB Material: FR4 ISOLA 370HR
  • No. of layers: 6
    • Top Layer (Component, Signal Layer, 90 Ω differential)
    • Ground Plane
    • Signal Layer
    • Power Plane
    • Ground Plane
    • Bottom Layer (Component, Signal Layer)

Components and Connections

Primary Side

Figure 1. AD-PAARRAY3552R-SL Top Side

Power Supply Connectors

These connectors are used to supply +48 V to the entire circuitry. The AD-PAARRAY3552R-SL provides an option for the user to use either a barrel jack connector or a two-wire terminal.

  • P1 → Barrel connector jack. Use this port if a 5.5 mm x 2.5 mm barrel jack adapter is preferred.
  • P2 → Two-port terminal connector. Port for supply power through non-terminated wires. Ensure proper connection to the positive and negative terminals of the power supply.

Supply power to either P1 or P2 only and not at the same time
Supplying power to both terminals may cause permanent damage to the device.

LED Indicators

Three indicator LEDs to display the board's current status:

  • DS1 → Indicates that a fault event (overvoltage or overcurrent).
  • DS2 → Indicates that a fault event (overtemperature).
  • DS3 → Indicates normal operation and good power regulation.

Peripheral Connectors

These connectors are used for debugging, programming, and communication between the software and hardware.

  • P5USB-to-UART Serial Communication through micro-USB to USB cable
  • P6 → Programming and debugging using 10-pin SWD cable


Hardware switches used to reset specific devices:

  • S3 → MAX32666 Microcontroller Reset

Test Points

The reference design board is comprised of several test points. The table below describes some of the most significant test points and their descriptions.

Figure 2. AD-PAARRAY3552R-SL Test Points

Test Points
TP Name Description Voltage
TP6 U2 LTC7000 Output +48 V
TP8 U3 ADM7172 LDO Output +5 V
TP9 U4 LT3042 LDO Output +5 V
TP10 U5 LT3042 LDO Output +5 V
TP11 U6 MAX17643 Output +5.6 V
TP12 U7 ADM7170 LDO Output +3.3 V
TP13 U8 ADM7170 LDO Output +1.8 V
TP14 U9 ADM7150 LDO Output +5 V
TP15 U10 LT3471 Positive Output +12 V
TP16 U10 LT3471 Negative Output -12 V

Pin Turrets and Hooks

The AD-PAARRAY3552R-SL is designed for specific power amplifiers and is used on the RF signal chain, as shown below.
Figure 3. RF Signal Chain

The bias lines of these amplifiers must be connected to the designated pinouts on the reference design board. Refer to the table below for the correct pin assignments.

Pin Assignments
Pin NameDescription Pin Type
5V0_SW RF Switch +5 V Pin Hook
EN_SW RF Switch Enable Pin Hook
5V0_PDA Pre-driver Amplifier +5 V Pin Hook
5V0_DA Driver Amplifier +5 V Pin Hook
EN_DA Driver Amplifier Enable Pin Hook
VDC1 Doherty LDMOS Carrier Drain Pin Hook
VDP1 Doherty LDMOS Peaking Drain Pin Hook
VGC1 Doherty LDMOS Carrier Gate Pin Hook
VGP1 Doherty LDMOS Peaking Gate Pin Hook
VDC2 Doherty GaN Carrier Drain Pin Turret
VDP2 Doherty GaN Peaking Drain Pin Turret
VGC2 Doherty GaN Carrier Gate Pin Hook
VGP2 Doherty GaN Peaking Gate Pin Hook
VD1 GaN Main Drain Pin Turret
VD2 GaN Peak Drain Pin Turret
VG1 GaN Main Gate Pin Hook
VG2 GaN Peak Gate Pin Hook

Secondary Side

Figure 4. AD-PAARRAY3552R-SL Bottom Side

SMD Packaging Provision

  • For easy evaluation, the board incorporates unpopulated SMD chip pads for 1210, 1206, 0805, and 0603 packaging. This allows the user to easily install a capacitive load of their choice.

System Evaluation

Equipment Needed

  • One (1) MAX32625PICO rapid development platform with 10-pin SWD cable and with updated firmware: see firmware update instructions
  • One (1) +30 V to +60 V programmable power supply
  • Two (2) micro-USB to USB cable
  • One (1) Signal Generator
  • One (1) Spectrum Analyzer
  • Two (2) SMA to SMA male cables
  • One (1) high-speed oscilloscope
  • One (1) oscilloscope probe
  • One (1) 10 nF capacitor (optional)
  • Host Windows PC:

General Setup

Figure 5. Hardware Connections Diagram

  1. Connect the 10-pin SWD cable to port P6 of the AD-PAARRAY3552R-SL.
  2. Connect the other end of the SWD cable to the MAX32625PICO.
  3. Use the micro-USB to USB cable to connect the MAX32625PICO to PC or laptop. This connection allows the user to upload firmware to the board.
  4. Then, connect the other micro-USB to USB cable to port P5. This connection enables USB-to-UART communication.
  5. Connect the positive terminal of the +48 V power supply to port P2.1.
  6. Connect the negative terminal of the +48 V power supply to port P2.2.
  7. Turn on the bench power supply. You will notice that DS3 (Green LED) will lights on.


AD3552R DAC Settling Time

The system allows an ultrafast sub-µs voltage settling time of GaN gates from pinch-off to the normal operating voltage by using the AD3553R dual-channel, ultrafast, 16-bit DAC. The typical voltage transition time from GaN pinch-off to its normal operating voltage is shown in the figure below.

How to measure

Measure the voltage settling time of the AD3552R DAC by following these steps:

  1. Connect a 10 nF capacitive load on one of the gate pins. The VG1 was used for this demo; alternatively, a through-hole or an SMD capacitor can be used.
  2. Connect the positive terminal of the oscilloscope probe to the VG1 pin and the negative terminal to the GND.
  3. On the GUI, users can choose a voltage from -10 V to +10 V. For this demo, the voltage level was shifted from -8 V pinch-off voltage to -2.5 V normal operating voltage, and vice versa.
  4. The oscilloscope will display the voltage level transition from -8 V to -2.5 V and -2.5 V to -8 V, as shown in the figures below.

RF Signal Chain Integration

The system is designed to provide biasing on a complete transmitter signal chain, as specified below.

Figure 6. RF Signal Chain

The below table shows the list of RF power amplifiers and switches used for this demonstration:

Device Part Name
RF Switch HMC849A
Pre-driver Amplifier ADL5611
Driver Amplifier ADL5611
First-stage GaN Amplifier HMC8500
Second-stage GaN Amplifier HMC8500

HMC8500 Specifications

  • < 10 W, 0.01 GHz to 2.8 GHz GaN Power Amplifier
  • Supply voltage: VDD = 28 V at 10 0mA
  • Pinch-off voltage: VGG = -8 V
  • Biasing Sequence:
    • Power-up:
      1. Set VGG to -8 V to pinch-off the drain current.
      2. Set VDD to 28 V.
      3. Adjust VGG with more positive voltage (approximately -2.5 V to -3 V) until a quiescent of IDD = 100 mA is obtained.
      4. Apply RF signal
    • Power-down:
      1. Turn off the RF signal.
      2. Set VGG to -8 V to pinch-off the drain current.
      3. Set VDD to 0 V.
      4. Set VGG to 0 V.

These sets of instructions involve using multiple bench power supplies and manually adjusting and turning it on/off. This method carries a high-risk of damaging the amplifier due to potential human-errors.

The AD-PAARRAY3552R-SL addresses these challenges and automates the bias sequencing, while also integrating a fault event protection and condition monitoring.

Hardware Connections

Follow the instructions provided in the General Setup section, as illustrated in Figure 5, and proceed with the following steps:

  1. At this point, it is assumed that the software setup section is completed.
  2. Set the signal generator with the following settings:
    • Frequency: 2.4 GHz
    • Power level: -40 dBm
  3. Set the spectrum analyzer with the following settings:
    • Center frequency: 2.4 GHz
    • Frequency Span: 500 MHz
    • Resolution: Adjust depending on your choice.
    • Amplitude: +20 dBm
    • Marker is at 2.4 GHz
  4. Don't turn on the signal generator yet.
  5. Cascade the two HMC8500 GaN power amplifiers as shown in Figure 7 below.
  6. Connect the RF input/output of the signal chain to the signal generator and spectrum analyzer, respectively.
  7. For safety measures, turn off the bench power supply.
  8. Connect the GND pin of the two HMC8500 to the GND pin of the AD-PAARRAY3552R-SL board.
  9. Connect the gate pins (VGG) of the two HMC8500 to the VGC2 and VGP2 pins of the AD-PAARRAY3552R-SL board, respectively.
  10. Connect the drain pins (VDD) of the two HMC8500 to the VDC2 and VDP2 pins of the AD-PAARRAY3552R-SL board, respectively. Refer to the figure below.
  11. Set the power supply voltage to +28 V before turning it on.
  12. Connect the micro-USB to USB cable to Port P5 of the AD-PAARRAY3552R-SL and the other end of the cable to the computer.
  13. Open the GUI Application. In the GUI Homepage, click the Go button under the “Device Monitoring and Control” as shown below.
  14. It will show the GUI dashboard. On the device connection, choose the correct Serial Port. Then, press “Connect”.

System Performance

Fault Event

The system can protect itself against undesirable fault incidents, such as overvoltage, overcurrent, and overtemperature events. The on-board LTC7000 handles overvoltage (OV) and overcurrent (OC) fault detection, while the MAX6516 is responsible for temperature monitoring and detection.

The table below shows the preset threshold for each parameter.

Safety Features
Fault Event Fault Threshold Limit
Overvoltage +55 V
Overcurrent 3.5 A
Overtemperature +75°C

Users can define the fault threshold limits based on their application by adjusting resistor values. Consult the schematic for the resistor values.

Fault Time Response

The system also exhibits fast fault detection and flagging.

Figure 8 shows the time from when the LTC7000 detects the fault and sends a signal to the microcontroller.

Figure 8. Fault Detected Time

Figure 9 shows the time for the microcontroller to process the fault signal coming from the LTC7000 before performing the required power down sequencing.

Figure 9. Fault Flag Time

Thermal Performance

The figure shows the temperature of the AD-PAARRAY3552R-SL board in normal operating conditions. This is the situation when all of the bias pins are sourcing their specified loads under normal operations.


Design and Integration Files

Further Help

For questions and more information about this product, connect with us through the Analog Devices Engineer Zone.

Navigation -

resources/eval/user-guides/ad-paarray3552r-sl/hardware.1707699640.txt.gz · Last modified: 12 Feb 2024 02:00 by Joyce Velasco