I have some issue on a new board. I already used the 5329 in many other boards using the recommended 2.2nF capacitor and a 47k pullup. Programming using the 2 wire JTAG works fine with both the old FET430UIF (the gray box one) and the new one (the black rounded one).
However on this new design it says 'device not found' (and with a scope the signal is *way* too much rounded). From the schematic the UIF output impedance is 100 ohms. On the line I have:
- About 10cm of AWG 24 wire from the UIF to the board (box connectors);
- A WE 82402304 ESD suppressor (max 17pF at 1MHz);
- The filter capacitor (ceramic EIA0603 SMD);
- A BC817 BJT (external reset from a supervisor). I reckon some pF of collector capacitance (the datasheet says 3pF typical). The base is actively pulled down by the supervisor;
- About 10cm of 0.15mm trace to the MCU (it's a little long but should work); about 10pF?
Removing the capacitor makes the SBW work perfectly, but of course there is no filtering for whatever noise floats into the board; and since it's a full bridge motor controller I am worried;
What is the recommended solution? I can try with a smaller (say, 1 or 1.5nF) capacitor, but would be efficient as a filter?
