Multiplexing in frequency domain using a bank of high-Q micro-resonators is an emerging method of reading out large arrays of transition-edge sensors and kinetic-inductance detectors. Low-power digitization of the resultant wide multi-GHz frequency band (e.g., 2-8 GHz) using a broadband superconductor analog-to-digital converter (ADC) enables high fidelity digital readout with immunity from noise, interference and cross-talk. HYPRES, Inc. has recently demonstrated a series of broadband digital radio receivers, built around a fast superconductor ADC. This ADC has low noise, low power, high linear dynamic range, and high radiation resistance. HYPRES proposes to design a similar ADC which is optimized for readout of a frequency-multiplexed sensor array such as that in the MicroSpec far-infrared spectrometer now being developed by NASA GSFC for future space missions. The superconductor ADC can be closely integrated and matched with the cryogenic sensors, enabling both reduction in system power and scaling to large imaging arrays. During Phase I, HYPRES will adapt a phase modulation-demodulation ADC for broadband (8 GHz) input, layout and fabricate an IC combining ADC with digital readout circuitry, and measure ADC performance with RF tones and an RF comb to simulate the frequency-multiplexed output of a sensor array. We will also assess the digital readout system for noise and thermal budget, and design the array interface for Phase II implementation. During Phase II, HYPRES will work with GSFC to integrate the ADC with a system testbed for the MicroSpec spectrometer and demonstrate its performance.