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OPA569 - How to connect Parallel Out pins for more than 2 devices

Matt Heston
Prodigy 10 points
Other Parts Discussed in Thread: OPA569

I have a linear TEC driver application that I need to source 10A with an output voltage very close to the VCC rail. The best solution I have found so far is to parallel 5 OPA569 devices. The datasheet shows 2 devices with device1-> parallel_out1 (pin2)  connected to device2-> parallel_out1 and device1-> parallel_out2 (pin9)  connected to device2-> parallel_out2.

Can anyone confirm the proper connection for more devices? Do I simply connect all of the parallel_out1 (pin2) pins together and connect all of the parallel_out2 (pin9) pins together or is there some other connection scheme like daisy-chain?

The datasheet indicates almost nothing about these pins and the load sharing circuitry. Does anyone have any indication of how these pins work internally?

Thanks,

Matt

  • 0
    Prodigy 210 points

    I have similar questions. My assumption is that the parallel pins are simply connected together as with two devices, but would like confirmation.

    Can anyone offer some insight here?

  • 0 in reply to Benjamin Sprague
    TI__Guru* 93105 points

    Hi Matt,

    You should be able to expand on the two parallel power op amp connections shown in Fig. 14 of the OPA569 datasheet. The upper circuit showing "inputs connected in parallel" would simply involve connecting an A3, A4, etc. as A1 and A2 are connected to each other. The "parallel out 1,"  the "parallel out 2," and outputs would be connected together in common groups.

    The Amplifier A1 as “master”, A2 as “slave” is could also be used, with A3, A4, etc. being driven by A1 as A2 is. Again, the "parallel out 1,"  the "parallel out 2," and outputs would be connected together in common groups.

    Note what the datasheet on Pg. 18 has to say about the two configurations, "Figure 14 shows two ways to connect the input terminals. When the amplifier inputs are connected in parallel, the effective offset voltage is averaged and the bandwidth and slew rate performance are the same as that of a single amplifier. It is also possible to use one amplifier to be the “master” and connect the other inputs to a voltage within the common-mode input range of the amplifier; however, slew rate and bandwidth performance will be degraded."

    Therefore, it may be advantageous from a an ac performance standpoint to use the "inputs connected in parallel" configuration over the other.

    Regards, Thomas

    Precision Amplifiers Applications Engineering