QPA2612 continious operation

RF Solutions RF Power Amplifiers
1

Hi everyone,

I’m currently working looking to integrate the Qorvo QPA2612 (8-12 GHz, 12W GaN-on-SiC) for our PA stage.

My primary challenge is that we need to run this amplifier in Continuous Wave (CW) mode, and I’m looking for some real-world sanity checks on my thermal and RF layout math before we spin a very expensive board.

Here is the current design context:

  • The Heat Load: Running at the recommended 24V bias, aiming for ~12W RF output, I’m calculating roughly 15W to 16W of continuous heat dissipation.
  • The Cooling Solution: We are using an active cooling loop (cold plate and copper coin under thermal pad of the PA).
  • The Component Choice: I initially looked at the 5W QPA2611, but its internal thermal resistance is nearly 10 °C/W. The 12W QPA2612 actually seems easier to cool because its is an incredible ~2.8 °C/W, meaning the thermal bottleneck is entirely on my PCB layout.

I’m hoping to get some advice on a few specific areas from anyone who has worked with this Qorvo family (QPA2610/11/12):

1. CW Performance vs. Datasheet Pulsed Curves

Almost all the large-signal performance plots in the datasheet (PAE, Output Power, Drain Current) are characterized using a 100 µs pulse width at a 10% duty cycle. Has anyone run the QPA2612 hard in CW? Assuming I can keep the baseplate strictly clamped at 50°C or lower, does the continuous thermal steady-state cause any severe gain droop or efficiency penalties that aren’t captured in the pulsed graphs?

2. PCB Thermal Path: Embedded Copper Coin vs. Via Array

To handle the 16W of CW heat through the 5x5 mm QFN center paddle, a standard 1.6 mm PCB via array seems like it will introduce too much thermal resistance (estimating ~2.0 °C/W, which costs me 32°C right off the bat).

  • I am heavily considering using an embedded solid copper coin in the PCB to mate the backside paddle directly to the cold plate.
  • The RF Question: Does a solid copper coin introduce any parasitic inductance issues for the RF ground at 12 GHz compared to a tightly packed, plated-through microvia array?

3. General Layout Traps

Are there any quirks with the QPA261x package or matching that I should watch out for?

Any insights, battle scars, or application notes you can share would be hugely appreciated!

Thanks in advance.

2

QPA2612 can be used under long pulse (> 1 ms) and CW applications with
the following considerations:

  • Output power will be about 0.5 dB lower than represented under data sheet pulsed
    (100us/10%) conditions
  • Dissipated power under nominal data sheet conditions (VD = 24 V , IDQ = 250 mA) will be
    approximately 23W (higher VD will increase Pdiss proportionally)
  • This will require using a coined PCB to properly manage the device thermals. The coin must be connected to the PCB GND, to avoid any issues with inductance to GND. This is particularly important for QPA2612, where the entire ground connection is through the center paddle.
  • A thermal via pattern, like that used for the Qorvo evaluation board, is only adequate for
    maintaining good thermal performance above about 10W of total dissipated power

Links to application notes for further study:

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