link to page 10 link to page 10 link to page 10 link to page 10 link to page 12 link to page 11 link to page 11 AD7940TYPICAL PERFORMANCE CHARACTERISTICS Figure 5 shows a typical FFT plot for the AD7940 at 100 kSPS Figure 7 shows a graph of the total harmonic distortion versus sample rate and 10 kHz input frequency. Figure 6 shows the the analog input frequency for various supply voltages, while signal-to-(noise + distortion) ratio performance versus the Figure 8 shows a graph of the total harmonic distortion versus input frequency for various supply voltages while sampling at the analog input frequency for various source impedances (see 100 kSPS with an SCLK of 2.5 MHz. the Analog Input section). Figure 9 and Figure 10 show the typical INL and DNL plots for the AD7940. 0110VDD = 4.75VFSAMPLE = 100kSPSFSAMPLE = 100kSPS–20TA = 25 ° CFIN = 10kHz105SNR = 84.48dBV–40SINAD = 84.35dBVDD = 3.6VDD = 3VTHD = –98.97dBVDD = 2.7VSFDR = –100.84dB100–60VDD = 4.3V–8095(dB)THD (dB)–100V90DD = 5.25VVVDD = 4.75VDD = 2.5V–12085–140 03305-0-019 –160 03305-0-021 80010k20k30k40k50k10100FREQUENCY (kHz)INPUT FREQUENCY (kHz) Figure 5. AD7940 Dynamic Performance at 100 kSPS Figure 7. AD7940 THD vs. Analog Input Frequency for Various Supply Voltages at 100 kSPS 90110FSAMPLE = 100kSPSFSAMPLE = 100kSPSTA = 25 ° CTA = 25 ° C105VDD = 4.75VV100DD = 5.25VVDD = 4.75V85RIN = 10 Ω 95VDD = 4.3VRIN = 50 Ω V90DD = 3.6VRIN = 100 Ω SINAD (dB)THD (dB)VDD = 3V8085VDD = 2.5VVDD = 2.7V8075 03305-0-020 75RIN = 1000 Ω 03305-0-022 101007010100INPUT FREQUENCY (kHz)INPUT FREQUENCY (kHz) Figure 6. AD7940 SINAD vs. Analog Input Frequency Figure 8. AD7940 THD vs. Analog Input Frequency for Various Supply Voltages at 100 kSPS for Various Source Impedances Rev. A | Page 9 of 20 Document Outline Table of Contents Specifications1F Timing Specifications Absolute Maximum Ratings ESD Caution Pin Configurations and Function Descriptions Terminology Typical Performance Characteristics Circuit Information Converter Operation Analog Input ADC Transfer Function Typical Connection Diagram Digital Inputs Modes of Operation Normal Mode Power-Down Mode Power vs. Throughput Rate Serial Interface Microprocessor Interfacing AD7940 to TMS320C541 AD7940 to ADSP-218x AD7940 to DSP563xx Application Hints Grounding and Layout Evaluating the AD7940 Performance Outline Dimensions Ordering Guide