An ICL7660-based negative rail daughter board.
See my eevblog.com forum thread for lots of oscilloscope screenshots as I tested various iterations of this design.
This board has been tested using the dutch oven faraday cage:
Performance matches that of the prototype (see the eevblog.com forum thread).
Noise into a 1k load:
Noise with power supply disconnected (i.e., noise floor of measurement system):
This indicates that the ~750kHz spikes are not coming from the ICL7660 board (perhaps this is due to the switch-mode power supply inside of the scope?).
Initial board design.
PDF.
This board design is Open-Source Hardware. It is licensed under the MIT License. It was designed by Jason Pepas.