A Two-Point Modulation Spread-Spectrum Clock Generator With FIR-Embedded Binary Phase Detection and 1-Bit High-Order ΔΣ Modulation

Abstract

This paper describes a spread-spectrum clock generation method by utilizing a Δ∑ digital PLL (DPLL) which is solely based on binary phase detection and does not require a linear time-to-digital converter (TDC) or other linear digital-to-time converter (DTC) circuitry. A 1-bit high-order Δ∑ modulator and a hybrid finite-impulse response (FIR) filter are employed to mitigate the phase-folding problem caused by the nonlinearity of the bang-bang phase detector (BBPD). The Δ∑ DPLL employs a two-point modulation technique to further enhance linearity at the turning point of a triangular modulation profile. We also show that the two-point modulation is useful for the BBPLL to improve the spread-spectrum performance by suppressing the frequency deviation at the input of the BBPD, thus reducing the peak phase deviation. Based on the proposed architecture, a 3.2 ㎓ spread-spectrum clock generator (SSCG) is implemented in 65 ㎚ CMOS. Experimental results show that the proposed SSCG achieves peak power reductions of 18.5 ㏈ and 11 ㏈ with 10 ㎑ and 100 ㎑ resolution bandwidths respectively, consuming 6.34 ㎽ from a 1 V supply.