This design is a close adaptation of the concept presented by:
Minh-Hai Nguyen; Cong-Kha Pham A wide frequency range and adjustable duty cycle CMOS ring voltage controlled oscillator https://ieeexplore.ieee.org/abstract/document/5670690
This design has seven 7-stage ring oscillators that have a final stage NAND which is takes as input
the inverter chain and the ena wire - that is, the oscillator should only run when ena is high.
The oscillators are all tied at their NAND-outputs to a single node which passes the signal through an "inverter bias" system that are biased using Harald Pretl's vDAC system which uses the first 4 input pins to select a voltage:
https://github.com/iic-jku/tt03-tempsensor/tree/main/src
Note: This circuit is only active when ena is enabled.
The inverter-bias system pass through two D-flip flops connected in series with their set signals tied high
and reset being connected to the rst_n control wire and their clocks being controlled by CLK. Finally,
these are passed through a ena-enabled AND which gates the final output of the TRNG.
Simulate the analog, hope for the best.
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | signal | sample | |
| 1 | control 1 | ||
| 2 | control 2 | ||
| 3 | control 3 | ||
| 4 | |||
| 5 | |||
| 6 | |||
| 7 |