SPX Step Response

How does Superpower compare with other voltage regulators? See the oscillograms below and judge for yourself. Top trace is the output current measured with a Tektronix current probe. The more important bottom trace is regulator output voltage, which should be perfectly flat for an ideal regulator. See notes below for more information on the tests.

Belleson SPX78 leading edge

SPX78 250mA dynamic response

SPX settles in less than 1µsec for leading edge of a 250mA current step.


LT3045 leading edge

LT3045 250mA dynamic response


Sparkos Labs leading edge

Sparkos 250mA dynamic response


TPS7A4700 leading edge

TPS7A4700 250mA dynamic response


Dexa 2 leading edge

Dexa 2 250mA dynamic response

Belleson SPX78 trailing edge

SPX78 250mA dynamic response

SPX settles in less than 1µsec for trailing edge of a 250mA current step.


LT3045 trailing edge

LT3045 250mA dynamic response


Sparkos Labs trailing edge

Sparkos 250mA dynamic response


TPS7A4700 trailing edge

TPS7A4700 250mA dynamic response


Dexa 2 trailing edge

Dexa 2 250mA dynamic response


Notes

Measurements are taken in the same test socket, with the same input stimulus and output sense for all devices. Measurements may differ from those you see in manufacturers' data sheets because of different setup, e.g. input or output capacitance, placement of sense device, wire lengths, etc.

Maximum output current is different for the various devices. To make it a fair test, the current step is 250mA, which is ½ the maximum for the lowest output devices. All regulators also have 100µF output capacitance and a 500Ω resistor for a 24mA DC load, which helps the trailing edge response settling time.

The LT3045 and TPS7A4700 are both surface mount monolithic devices that require a PCB to allow them to be plugged into a TO-220 style test socket. The tested devices were, when purchased, mounted on a PCB with MLCC capacitors already connected. Replacing the MLCCs with tantalum on the TPS7A4700 PCB significantly improved performance, and the measurements you see here are with 10µF tantalum.

The SPX is so fast that a ferrite bead had to be added to the pull-down transistor to prevent high frequency ringing in the response.


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