2025-06-03 Buck-Boost design

In many projects the power supply is not done properly and its really hard to make the external power connection small, stable and aesthetic. So i decided to design a breakout board with USB C connector and an integrated power regulator. It will have adjustable output of 2.5-8V and a maximum output current of 2A. It will have a relative wide input voltage, 2.5-12V. Cost efficiency and small form factor are also important. This spec will work for most normal projects

Before PCB design all component optimization is done on a eval board from Texas instrument for the TPS6360 regulator.

To find correct components that work well and are as cheap as possible calculations are performed for the inductor, output/ input capacitors and feedback resistors. The equations used are normally found in the datasheet together with recommended values.

The following shows the worst case calculations to be used when finding the best components  

Now when the calculations are done it's easier to find components that might work in the design.

Inductors.

Taitech L=1uH, Isat=8.5A, I=5A , 0.5USD

Taitech L=1.5uH, Isat=12A, I=7A , 0.14USD

Delta electronics L=1.5uH, Isat=8A, I=5.5A, 0.25USD

Capacitors will be tested to optimize the price, voltage and the minimum amount to reach correct capacitance in relation to DC bias. The DC bias is the decrease of capacitance due to DC bias which in this design is 8V as worst case.

Next is to solder different components to on the eval board and start measuring

To be continued.....

2025-06-03 DIY Diffprobe

Sometimes you need a diffprobe to measure differential signals or to just protect your scope when you measure on non isolated circuits that can create groundloops in the equipment. I have a diffprobe that work good for really high voltages up 5.6kV but its resolution is not well suited for low voltage electronics.

The plan was to design my own diffprobe so a started to google and stumbled upon a DIY diffprobe that seemed to work well and had well documented data.

https://hackaday.io/project/169390-a-10x-100mhz-differential-probe

Also i realized that i would need to get a VNA (vector network analyzer) to characterize the impedance.

So i just used supplied schematic and gerberfiles.

The original probe had a attenuation of 10x but i wanted a 1x probe due the lower measured voltages.

So the major specs of the probe are:

BW: 0-100MHz

Att: 1x

Vin: 35Vmax Common Mode

Cost: ~65usd inc casing, usb connector and PCB's

It was really easy to build the probe and i could even find a topic on which components to replace to achieve the 1x attenuation.

The only design i did this time is the 3D Cad of the casing. Also i had a bunch of uUSB connectors left from a previous project so i designed also a tiny PCB to mount the connector on and to have that as power supply connection for the probe instead of having some big DC jack.

The major issue was when i wanted to calibrate the probe and measured really high spikes at each switch transition, i could not find what the issue was. So i contacted the designer of the probe and he was very helpful. He tried to simulate in LT spice which errors would give the really high transients and by that try to point out where to look. 

He discovered that i had probably put wrong resistor values in a divider. 3k and 36k instead of 30k and 360k. Well with that corrected i was able to calibrate the probe and with some fine tuning both with trim capacitors and some soldered pF caps it now works perfect.

Pics below show the really high transients at Ch2 and the how it looks when correct resistors are mounted.