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TPS84A20 at 6v?

Other Parts Discussed in Thread: TPS84A20

I have an application which looks perfect for the TPS84A20, except the output voltage required is +6V. From the equation, it looks like a value of 159 ohms would set it to 6V. With the higher output voltage, the efficiency would be expected to be higher, and the inductor current to be less. Is there any reason why this would not work?

  • Hi Gordon,

    We no not characterize higher than 5.5V.

    Increasing to 6V will increase the power dissipation, effecting the thermal performance. Also, the ripple current through the inductor may increase, effecting the current limit threshold.


  • Thanks. I received the EVM, and tested it at 5V and 6V. The load regulation is extremely poor, even at 5V output, it drops around 10% at 6 amps or so, so I do not think it will be useable. I need load regulation of about 2.5%. The data sheet says the load regulation should be 0.2%, but this is not the case for the EVM I received.

    Incidentally, for a buck regulator, the smaller the input/output differential, the better the efficiency, normally. The curves in the data sheet seem to confirm this. Are you referring to the quiescent dissipation of the part?

  • The load regulation at 5V should not be that poor. How are you measuring it? You must measure the Vout at the device, not at the load. Look at the power dissipation graphs for this device. As the output voltage increases, the output power increases, therefore the power dissipation must go up as well.

  • Voltage was measured at the red VOUT test point on the board, and before the amp meter and load.

    I was looking at the first curve on P8, which shows the efficiency going up as the output voltage goes up. I was considering putting two of them in parallel, since our typical load is 9-10 amps. If the output current is limited to 5 amps, that would presumably keep the dissipation under control? The bigger problem is the regulation. I will try to find time to re-check in the next day or so.