Renesas and Hitachi develop high-speed, high-precision automotive A/D converter circuit
Renesas Electronics and Hitachi announced a technology collaboration to enable continuous-time digital calibration of a delta-sigma (ΔΣ) modulator and an analog-to-digital (A/D) converter circuit.
Designed to boost the performance of ΔΣ A/D converters for stable performance under the harsh conditions required for automotive semiconductor devices, the new technology comprises (1) enhanced precision by using a least mean square (LMS) algorithm to measure and calibrate the transfer function of a continuous-time ΔΣ modulator, and (2) the world’s first multi-rate LMS search algorithm, which lowers the order and operating frequency of the coefficient search circuit and FIR digital filter to reduce power consumption. The 28 nm process was used to implement a multi-stage ΔΣ A/D converter employing sequential integrators operating at high speed.
Previously, digital calibration circuits were required to operate at an oversampling frequency of A/D converters, but the new circuit reduces the operating frequency to one-fourth the previous frequency. As a result, high-speed, high-precision operation with a signal bandwidth of 15 MHz and dynamic range of 74.3 dB is achieved when operating at an oversampling frequency of 480MHz. By reducing the digital calibration circuit operating frequency to 120MHz, low-power operation is also achieved, with 37mW power consumption (analog:19mW, digital:18mW). In addition, the new technology has been confirmed to provide stable performance over a wide temperature range, proving that it is highly robust and capable of stable operation under punishing conditions.
The results of this joint effort with Hitachi were presented by Renesas on February 18 at the International Solid-State Circuits Conference (ISSCC) 2020.