picoMUX: microcontroller based time-domain multiplexing readout for kilopixel TES arrays

Advances in cryogenic SQUID-based time-domain multiplexing (TDM) have outpaced their warm readout electronics. Next generation CMB telescopes are baselining kilopixel TES arrays with few viable electronic options. We present picoMUX, a new TDM readout electronics architecture that replaces the FPGA typically used in such systems with a complement of modern microcontrollers. Designed around the current generation NIST multiplexer, it fully exploits its differential nature and two-level switching. The system achieves the desired timing metrics (sub {\mu}s row dwell time) while reducing cost, complexity, and power consumption over a comparable FPGA solution. Preliminary noise measurements are consistent with expectations and show no evidence that the novel architecture introduces excess noise. picoMUX demonstrates how recent advances in microcontrollers enable simpler, low-power, low-cost TDM readouts for kilopixel TES arrays.