Filter designfrom Σ-Δ ADC to incremental Σ-Δ ADC Donglijun 2013-4-28 TJU ASIC center
index filter design of Σ-Δ ADC filter design of incremental Σ-Δ ADC difference between the two filters
filter design of Σ-Δ ADC • Σ-Δ ADCs are widely used in telecommunication and multimedia applications. • The key property of Σ-Δ ADC • ①to achieve high resolution do not rely on precisely matched analog elements • ②rely on oversampling, noise-shaping and digital post-filtering. • ③can be integrated well into today’s fine line-width CMOS technologies.
filter design of Σ-Δ ADC • Modulators of Σ-Δ ADC push the noise from low frequency rate to high frequency rate. So to achieve high resolution, the key point of Σ-Δ ADC is its digit filter’s suppression of high frequency. • The function of the filter are as follow: • ①filtering • ②decimating • ③coding • There is some parameters • for Σ-Δ ADC filter: • ①decimating rate(D) • ②bandwidth • ③SNR
Filter architecture CIC filter FIR filter(half band filter)
Introduction to incremental Σ-Δ ADC • Unfortunately, these classical ΣΔ structures are not well suited for instrumentation and measurement (DC) applications. • Require: • ①very high absolute accuracy and linearity • ②high dynamic range and signal-to-noise ratio • ③Hertz wide bandwidth(nearly DC input)
Filter design for IDC 3 Typical structure of decimation filter • CoI filter • Sinc filter(CIC) • Optimal filter Line frequency noise • S/H and the error of S/H • Periodic noise suppression digit filter Canceling periodic noise
Typical structure for IDC filter • Sinc filter(CIC) • Cascade Integrate Comb • CoI filter • Cascade Of Integrated
rotated sinc filter • From left to right D=32,64,128 bottom D=128
Design deference between Σ-Δ filter and incremental Σ-Δ filter
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