数据搜索系统，热门电子元器件搜索 

LTC232718 数据表(PDF) 15 Page  Linear Technology 

LTC232718 数据表(HTML) 15 Page  Linear Technology 
15 / 26 page LTC232718 15 232718fa For more information www.linear.com/LTC232718 applicaTions inForMaTion DYNAMIC PERFORMANCE Fast Fourier Transform (FFT) techniques are used to test the ADC’s frequency response, distortion and noise at the rated throughput. By applying a low distortion sine wave and analyzing the digital output using an FFT algorithm, the ADC’s spectral content can be examined for frequen cies outside the fundamental. The LTC232718 provides guaranteed tested limits for both AC distortion and noise measurements. SignaltoNoise and Distortion Ratio (SINAD) The signaltonoise and distortion ratio (SINAD) is the ratio between the RMS amplitude of the fundamental input frequency and the RMS amplitude of all other frequency components at the A/D output. The output is band limited to frequencies from above DC and below half the sampling frequency. Figure 8 shows that the LTC232718 achieves a typical SINAD of 95dB at a 500kHz sampling rate with a 2kHz input. SignaltoNoise Ratio (SNR) The signaltonoise ratio (SNR) is the ratio between the RMS amplitude of the fundamental input frequency and the RMS amplitude of all other frequency components except the first five harmonics and DC. Figure 8 shows that the LTC232718 achieves a typical SNR of 95dB at a 500kHz sampling rate with a 2kHz input. Total Harmonic Distortion (THD) TotalHarmonicDistortion(THD)istheratiooftheRMSsum ofallharmonicsoftheinputsignaltothefundamentalitself. The outofband harmonics alias into the frequency band between DC and half the sampling frequency (fSMPL/2). THD is expressed as: THD=20log V22 +V32 +V42 +…+VN 2 V1 where V1 is the RMS amplitude of the fundamental frequency and V2 through VN are the amplitudes of the second through Nth harmonics. POwER CONSIDERATIONS The LTC232718 provides two power supply pins: the 5V power supply (VDD), and the digital input/output interface power supply (OVDD). The flexible OVDD supply allows the LTC232718 to communicate with any digital logic operating between 1.8V and 5V, including 2.5V and 3.3V systems. Power Supply Sequencing The LTC232718 does not have any specific power supply sequencing requirements. Care should be taken to adhere to the maximum voltage relationships described in the Absolute Maximum Ratings section. The LTC232718 has a poweron reset (POR) circuit that will reset the LTC232718 at initial powerup or whenever the power supply voltage drops below 2V. Once the supply voltage reenters the nominal supply voltage range, the POR will reinitialize the ADC. No conversions should be initiated until 200μs after a POR event to ensure the reinitialization period has ended. Any conversions initiated before this time will produce invalid results. TIMING AND CONTROL CNV Timing The LTC232718 conversion is controlled by CNV. A ris ing edge on CNV will start a conversion and power up the LTC232718. Once a conversion has been initiated, Figure 8. 32k Point FFT of the LTC232718 FREQUENCY (kHz) –180 –60 –40 –20 –80 –100 –120 –140 –160 0 232718 F08 SNR = 95.3dB THD = –113dB SINAD = 95.2dB SFDR = –116dB 0 50 100 150 250 200 
