The ZS1100A is a successor to the IOT power profiler tool (ZS2102A) which I had designed earlier. There is a tear down on Hackaday for that tool. Many users suggested to add a power supply to the tool which would enable them to power their devices in the lab, without having to use a battery or another DC source. With the power supply integrated in to the tool, the users can set any output voltage and measure the current profile. 

With the addition of a power supply, several problems come up which needs to be addressed.

1. Stability under various load conditions

We have checked it for stability under various load conditions, like capacitive loading, inductive loads, pulsed loads etc. and is found to be stable at all output voltages.

2. Thermal considerations

Built-in thermal protection disables the outputs, if a high load is connected for a long period of time. A BLDC fan provides constant air flow within the tool to cool off the power transistors used in the output stages.

3. Output noise

Output noise is kept to below observable limits. The noise is so low that it enables the measurement of 1uA of current with a maximum error of 0.2uA.

4. Current limiting

The output current can be limited to any value between 0 to 1.5A using the GUI in steps of 10mA. 

5. Negative current (Current flowing into the positive terminal of the tool)

Inductive loads can feed some current back into the power supply under different conditions. The tool has circuits built to sink this current safely while keeping the output voltage constant. 

6. Output load regulation & Transient response

The main problem encountered when using a high value sense resistor is the output voltage regulation under high load. Since the sense resistor is used in a feedback loop, the drop across the sense resistor is compensated by the loop. Both the positive and negative terminals of the power supply output are sensed by the control loop. This ensures that the drop in the traces are compensated for. The output remains within 1mV of the set voltage even with 1A load.

7. Fuse

Also added a good old fuse for any failures. The fuse is a standard 5x20mm 5A cartridge .

8. ESD and transient protection

All the input and output ports feature ESD protection up to 8KV HBM. This is to ensure a robust and reliable product which can last long. The DC input jacks are protected with reverse voltage and transient voltage suppressors.

Some additional features

1. OLED display

The output current and set voltage and displayed on the OLED screen. In addition, the OLED displays various diagnostics and error messages

2. Digital IO

The tool captures 6 bit GPIO at 1Msps in sync with the current waveform. 4 of the GPIO have pull-down resistors of 100K connected to ground. 2 of them have 100K pull-ups to Vcc. This ensures that the tool can capture both active high and active low signals without any leakage. These inputs can be level shifted from 1.8V to 5V using the in-built level shifter. A 1MHz sampling clock is also given out at the digital IO port.


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