高速ADC基础.pdf高速ADC基础pdf,高速ADC基础TEXAS INSTRUMENTS Ana

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详细说明：高速ADC基础pdf,高速ADC基础TEXAS INSTRUMENTS Analog Input- Time Domain Frequency(Fin) igital Output Volts Time D5 D4 D3 D2 D1 DO 011111 2/FS 010 6-Bit D3 3/Fs 1 ADC D2 DI DO N-2/Fs01 101 1/FS000111 Fs1101 Clock ampling t1 t2 Fre Analog Input-Frequency Domain Digital Output- Frequency domain Frequency Fin requency Fin Fin In Power Po (dBm) (dBm) Harmonics 3. 4& 5 Harmonics, Fin x integer have aliased 3 4 32 凼风 Noise floor Frequency(Hz) Frequency(Hz) Fs/ 2-Nyquist Fin: Analog Input Frequency=1/(t2-t1) Harmonics: integer multiples of Fin(2×Fin,3×Fin,4×Fin,5xFin.) Fs: Clock Frequency Nyquist: Fs/2 Aliasing: the placement of frequencies Fs/2 (Nyquist )in the Digital Output Frequency domain, explained later in more detail XAS INSTRUMENTS SNR= Olo P P 10(s7N Digilal Oulpul- Freyuency dormain SFDR=10log1o(PS/P Frcqucncy Fin THD=10 1og10(Ps/P SINAD=10log10 Ps/PD+PN) ENOB=(SINAD-1.76)/6.02 Power Fundamental In this plot (dB) harmonic #3 Ds: Signal Power (red PN: Noise Floor Power(blue 6 24 would be Ph in the DD: Power of harmonics 2-6(black) SFDR calculation PH: Power of next highest spur(black) Al sincc it is the largest non Frequency (Hz) fundamental spur ldea|SNR=602×n+1.76 n number of bits TEXAS INSTRUMENTS Analog Input Frequency Nyquist Analog Input ADC capture Analog Input Frequency Nyquist Analog Input ADC capture XAS NSTRUMENTS ADC Oversampling ADC output Spectrum Analog Input Frequency < Nyquist Aw Fso/& Fso/4 3 x Fso/& Fso/2 ADC Undersampling ADC output Spectrum Analog Input Frequency Nyquist Fsu=14×Fso Ali Fsw/2 Compare Oversampling to Undersampling: In the adc oversampling time and frequency domain plots the adc output correctly represents Fin In the ADC Undersampling time and frequency domain plots the adC output Fin resembles a lower frequency(aliased frequency) TEXAS INSTRUMENTS 7a: Desired Aliasing. wideband signal Bw s Nyquist Good result ADC No Frequency 2 45 MHz(Nyquist 45 MHz 90 MHZ 135 MHz Fs=90 MSPS 7b: Desired Aliasing Wideband signal B Ws Nyquist Propcr Frcqucncy plannin Good result y ADo Inversion 2 Zones 45 MIIz(Nyquist 45 MHZ 90 MHZ 135 MHZ Fs=90 MSPS 7c: Undesired aliasing Widcband signal BW< Nyquist Improper Frequency planning Bad result Dark unrecoverable ADC information 45 MHz 90 MHz 135 MHZ 45 MHz(Nyquist) Fs=90 MSPS 7d: Undesired Aliasing Wideband signal BW> Nyquist 30 MHz(Nyquist) Bad resull Dark unrecoverable ADC Signal information 45 MHz 90 MHz 135 MHZ 30 MHZ ( Nyquist FS= 60 MSPS TEXAS NSTRUMENTS TEXAS INSTRUMENTS www.tl.com 12-Bit, 500-MSPS Analog.to-[ FEATURES 500-MSPS Sample Rate 12-Bit Resolution 10.5 Bits ENOB ·2 GHz Input Bandwidth SDRe 75dBc at-450-iihizand 500 MSPS oRB1rP SNRE646 dBFs at 450 MHz and 500 MsPs 2.2-Vpp Differential Input voltage APF LVDS-Compatible utputs Total Power Dissipation: 2. 2 W Offset Binary output Format output Data Transitions on the rising and Falling Edges of a Half-Rate Output clock TsDPcR DESCRIPTION The AD55463 is a 12-bit, 500-MSPS analog-to-digital converter 3-Y supply, while providing LVDS-compatible digital outputs switching cf the onboard track and hold (t&H)from dis high-impedance input. An internal reference generator is also pre TEXAS INSTRUMENTS A)Desired signal Desired Signal-180 degrees out of phase Desired signals add B)Signal Imperfections Subtraction Common mode operation Common modc noisc and Even order harmonics Even order harmonics 1. Driving Differential Inputs Single-Ended vs Little headroom Vpr(p-l VsE(p-p AD …-…-…-…-…-…---…-…-…--…--GND 2. Driving Differential Inputs Differentially +v More hea droom VDifr(p-p) D GND XAS NSTRUMENTS Z and TFADc ADS5547 WBC1-ITLB WBC1-IT (Note A) 100g 0.1uF 2 33g 25g 100 INM 15 VCM A Use lower series resistance(=5 Q2 to 10 Q2)at high input frequencies(> 100 MHz) ADC VCM pin sets common mode for transformer Reference Voltage Sets Dynamic Range Full-scale differential input pp= Vref x 1.33 Full-scale differential input pp=2xvie'TopvreTBottom

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