Exact Design of All-MOS Log Filters X.Redondo and F.Serra-Graells - PowerPoint PPT Presentation

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Exact Design of All-MOS Log Filters X.Redondo and F.Serra-Graells Design Department Institut de Microelectrònica de Barcelona Centre Nacional de Microelectrònica Spain 24th May 2004 X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Introduction Low-voltage MOS-C log circuits Generalization to non-linear capacitors Exact all-MOS proposal Design examples Conclusions X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions MOS log-mapping Instantaneous companding filters d ¯ dt = ¯ I ss A ¯ I ss + ¯ B ¯ I out = ¯ ¯ C ¯ I ss + ¯ D ¯ I in I in G V GB compression non-linear�integration expansion I D D S V ss 1 I ss 1 1 F s V DB V SB I in 1 -1 V in 1 F G G B V ss 2 I ss 2 1 F s -1 I in 2 V in 2 F weak inversion: G G V SB,DB ≫ VGB − VT O n V ssN I ssN 1 F s -1 I inM V inM F G G forward saturation: V DB − V SB ≫ U t externally�linear � High-frequency (bipolar) VGB − VT O e − VSB I D = I S e nUt Ut � Low-voltage IC = I D I S = 2 nβU 2 ? Non-linear capacitors t I S X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Introduction Low-voltage MOS-C log circuits Generalization to non-linear capacitors Exact all-MOS proposal Design examples Conclusions X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Compressors and expanders I ref I ref 1 × K × K I out I in C in I ref I ref V ref V ref V in V out C comp V − Vref ◮ Companding function: I = F ( V ) = I ref e I > 0 nUt ◮ Class-A operation: I max ≡ I ref 2 � KC comp ◮ Frequency compensation of input parasitics: ζ = 1 2 C in X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Integrators   · · · ¯ + 1 − 1 + 1 A =   τ 21 τ 22 τ 23 I tuno · · · single-coefficient linear ODE: V in V out dI out = ± 1 I cap τ I in C o dt non-linear ODE in the compressed domain: dV out = ± nU t Vin − Vout τ e ◮ Single phase ( + 1 nUt τ case) dt ◮ Operating point ensured circuit realization in the Q -domain: by the ¯ A matrix dQ out dV out Vin − Vout ◮ Half of G can be shared = C o = ± I tuno e nUt dt dt by the same row of ¯ A � �� � I cap ◮ Valid only for grounded τ = nU t C o I cap = G ( V in , V out ) linear capacitors I tuno X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Introduction Low-voltage MOS-C log circuits Generalization to non-linear capacitors Exact all-MOS proposal Design examples Conclusions X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Voltage-dependent capacitors dQ out = C dV out + dC dt V out dt dt � dV out I tun � dQ out dC f = C + V out dt dV out dt V in V out distortion due to: ◮ Signal swing ( V out ) C ◮ Non-constant capacitance ( dC dV out ) ◮ Valid for non-abrupt C - V Tuning compensation strategy ◮ Linear case reduction: I tun = C dC V out . dC + = f ( V out ) = 0 I tun ≡ I tuno I tuno C o dV out C o dV out X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Introduction Low-voltage MOS-C log circuits Generalization to non-linear capacitors Exact all-MOS proposal Design examples Conclusions X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Grounded NMOS device ◮ Single poly-Si structure � 1 0.9 ◮ Digital process 0.8 compatible � strong�inversion 0.7 ◮ High-density [F/m 2 ] � moderate 0.6 inversion C Co 0.5 / C gate ≫ C poly − poly 0.4 Vout weak�inversion 0.3 ◮ Strong non-linearity C 0.2 around V T O × 0.1 ◮ Low-voltage versus 0 -20 -15 -10 -5 0 5 10 15 20 distortion ? ( Vout - V )/ Ut TO (i.e. V ref vs V T O ) X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions I tun V T O U t Analytical compensation = 1 + ( V out − V T O ) 2 I tuno all-regions quasi-static C GG : √ � IC � √ n − 1 + 2 IC 1 − e − n C = C o √ � � V T O U t √ I tuno I tuno IC 1 + 2 IC 1 − e − ( V out − V T O ) 2 IC = ln 2 � � V in V out Vout − VT O 1 + e 2 nUt C for V out,ref ≥ V T O (i.e. IC ≫ 1 ): C U t = 1 − equivalent to add C o V out − V T O a positive signal-dependent tuning current. . . X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Circuit realization I tuno I mult I tun V T O U t = 1 + × I tuno ( V out − V T O ) 2 I tuno I tun I comp matched device in strong inversion: M2 V in V out C I comp = β 2 2 n ( V out − V T O ) 2 M1 I tun = I tuno + I tuno I S 2 V T O I tuno (2 n ) 2 U t I comp I mult tuning compensation synthesis: I comp I tun − I tuno I tun = I tuno + I tuno I mult I comp V T O I mult = I S 2 V ref (2 n ) 2 U t X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Introduction Low-voltage MOS-C log circuits Generalization to non-linear capacitors Exact all-MOS proposal Design examples Conclusions X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Third-order low-pass filter 2 1.5 THD [%] 1 0.5 0 -30 -20 -10 0 200 m ¹ Input-Amplitude/Full-Scale�[dB] ◮ 0.35 µ m technology ◮ f − 3 dB = 8 KHz f in = 2 KHz ◮ Poly-Si(dashed) versus ◮ V DD = 1.2V V ref = 0.6V NMOS(solid) results X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Second-order band-pass filter I tuno I mult I ref I ref 1 × K × K I in I out × I tuno I ref I ref I tun − I tuno V ref V ref V in V out I tun C 1 I tuno I mult × I tuno C 2 X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Second-order band-pass filter ◮ f o = 50 KHz and Q = 1 3 ◮ f in 1 = 46 KHz topology f in 2 = 54 KHz limitation 2.5 VTO proximity�effect ◮ Half full-scale input 2 ◮ V DD = 1.2V IMD [%] 1.5 ◮ 0.35 µ m technology multiplier saturation 1 0.5 • Ideal poly-Si (dotted) 0 • Simple NMOS (dashed) 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 Vref [V] • NMOS with tuning compensation (solid) X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Second-order band-pass filter 200 m ¹ X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Second-order band-pass filter current�sources translinear-loops MOS�capacitors and�mirrors telescopic�devices 200 m ¹ X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Second-order band-pass filter tuning-compensation band-pass�filter Overhead: 200 m ¹ ◮ Si area (no-routing) ∼ 0.04mm 2 (12% of 0.33mm 2 ) ◮ Static power ∼ 50 µ W (33% of 150 µ W) X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions Introduction Low-voltage MOS-C log circuits Generalization to non-linear capacitors Exact all-MOS proposal Design examples Conclusions X.Redondo and F.Serra-Graells IEEE ISCAS’04

Exact Design of All-MOS Log Filters Intro MOS-C Generalization All-MOS Examples Conclusions ◮ Analytical design of all-MOS log filters based on compensation of tuning currents ◮ Suitable for very low-voltage applications ◮ Compatible with digital technologies ◮ Area & power overhead proportional to filter order ◮ Technology dependence not critical ◮ Sub-micron low-voltage examples ◮ Extension to Class-AB operation?. . . X.Redondo and F.Serra-Graells IEEE ISCAS’04