German

The task for my master degree, which I have done at the Melexis (Erfurt, Germany), has been to find and realize a completely new circuit principle for the analog low speed driver of a -chip. The special problem was, to fulfill the hard USB specification 1.1 of the USB implementers forum with a low cost technology.

On the left hand side you can see a block diagram of the TH6503. This chip is functioning as a bridge between a microcontroller and the USB. All the USB protocol is implemented in its digital core and so the user really can concentrate on his application. Because of the serial interface, just a few pins are needed.

The block “USB-I/O” is the transceiver. It connects the digital core with the analog world. The critical part of this analog circuit is the low speed driver. It has to fulfill several criteria, like slew rate and slew rate matching. The crossover voltage is of special interest. After checking several known concepts a completely new idea did grow up and succeeded at the end.

For the layout the circuit has been split into several cells, for being more flexible in arranging. Most of the layout has been done by a professional layouter, the rest by myself. Assembling all the cells and doing the top wireing has been a quick procedure, because the Melexis is using the same layout program (Cadance Framework) like on University.

The simulation with SpectreS did show, that the circuit will work under all technology parameter and temperatures.

Because it takes some time to manufacture the chip, the circuit has been measured after finishing the master degree. The measurements are showing, that the circuit principle is working (symmetry ok).

Full speed measurement                                            Low speed measurement

 The master degree was graded with mark 1.3

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