Upcoming SlideShare
×

# SAR ADC's and industrial Applications

1,632

Published on

Published in: Education
3 Likes
Statistics
Notes
• Full Name
Comment goes here.

Are you sure you want to Yes No
• Be the first to comment

Views
Total Views
1,632
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
0
0
Likes
3
Embeds 0
No embeds

No notes for slide

### Transcript of "SAR ADC's and industrial Applications "

1. 1. EEE462 - Analog-to-Digital and Digital-to- Analog Converters SAR ADC and industrial Applications Ahmet İlker Şin 070203012 1
2. 2. Outlines Introduction to Successive Approximation ADC Summary of Convert Types Successive Approximation Example Literature Survey Comparison Between Published Data Market Survey industrial Applications 2
3. 3. Successive Approximation Converter Similar to the ordering weighing (on a scale) of an unknown quantity on a precision balance, using a set of weights, such as 1g, 0.5g, 0.25g, etc.Guess the answer, use a D/A to convert it to ananalog voltage and compare it to the voltagebeing measured – adjust your guess accordingly 3
4. 4. Successive Approximation Converter The timing diagram for a typical SAR ADC is shown in Figure 3. The functions shown are generally present in most SAR ADCs , but their exact labels can differ from device to device 4
5. 5. Successive Approximation Converter  Reliable  Capable of high speed  Conversion time is clock rate times number of bits Example with 8-bit, 2-MHz clock rate: Conversion time= (clock period) x (#bits being converted) Conversion time= (0.5 micro-sec) x (8-bits) = 4μs 5
6. 6. Summary of Convert TypesConverter Type Speed Resolution Noise Cost ImmunityVoltage/Frequency slow 14-24 good medium Dual Slope slow 12-18 good low Successive medium 10-16 little lowApproximation Flash (Parallel) fast 4-8 little high *Resolution given in bits. 6
7. 7. Successive Approximation Example Bit Voltage10-bit resolution or 1 .50.0009765625V of Vref 2 .25 3 .125Vin =0.6V 4 .0625 5 .03125Vref =1V 6 .015625 7 .0078125If we want to find the digital 8 .00390625value of Vin 9 .001952125 10 .0009765625 7
8. 8. Successive Approximation Example (cont.)MSB (bit 1)– Divide Vref by 2 = .5V– Compare Vref /2 with Vin– If Vin is greater, turn MSB ON– If Vin is less than Vref /2, turn MSB off– Compare Vin=0.6V and V= 0.5V– Since 0.6 > 0.5 → MSB =1 (turned on) 1 8
9. 9. Successive Approximation Example (cont.)Calculate the state of MSB-1 (bit 2)– Compare Vin =0.6V and V=Vref /2 + Vref/4 =0.5+0.25 = 0.75V– Since 0.6 < 0.75 → MSB-1 =0 (turned off)Calculate the state of MSB-2 (bit 3)– Go back to the last voltage value that causedit to be turned on (inthis case 0.5V) and add Vref/8 to it and comparewith Vin.– Compare Vin and (0.5 + (Vref/8)=0.625)– Since 0.6 < 0.625 → MSB-2 =0 (turned off) 1 0 0 9
10. 10. Successive Approximation Example (cont.) Calculate the state of MSB-3 (bit 4)Go back to the last voltage value that caused it to be turned on(in this case 0.5V) and add Vref/16 to it and compare with Vin.– Compare Vin and (0.5 + (Vref/16)=0.5625)– Since 0.6 > 0.5625 → MSB-3 =1 (turned on) MSB MSB-1 MSB-2 MSB-3 … 1 0 0 1 10
11. 11. Successive Approximation Example (cont.)Digital Results :MSB MSB-1 MSB-2 MSB-3 … LSB 1 0 0 1 1 0 0 1 1 0 Results : 11
12. 12. Literature SurveySeveral IEEE documents, company’s websites and on line newsletters areanalyzed. The table shows Comparison of the proposed ADC with otherpublished works The figure of merit (FOM) used in is referred here to compare the proposed ADC design with other published works. The FOM is defined as In stead of a power point of view, this FOM is from the aspect of energy, which concerns the total energy consumed in one full conversion cycle of ADC . Here the power doesn’t take into account the reference buffer and clock generation . Table summarizes the comparison results. Though power of the proposed SAR ADC is the lowest, the energy per sample of it is relatively higher compared to most of the listed works 12
13. 13. Comparison of the proposed ADC with other published worksTechnology 0.25μm 0.18μm 0.18μm 90nm 0.18μm 65nm(CMOS)Resolution (bit) 8 9 12 9 8 10Supply voltage (V) 1 1 1 1 1 1Sampling rate 100 K 150 K 100 K 20 M 400 K 1M(S/s)Input range (V) 1 0.5 N/A N/A 1 N/AENOB (bit) 7.9 8.2 10.55 7.8 7.31 8.75Power dissipation 3.1μ 30μ 25μ 290μ 6.15μ 1.9μ(W)FOM 130 680 167 65 97 4.4(fJ/conversion-step) 13
14. 14. Comparison Between Published Data Topology Bits Sampling Power Vdd Technology Rate Folding 8 70 MS/s 45 mW 3.3 V 0.8 µm and/ or 10 40 MS/s 65 mW 5V 0.6 µm Interpolating ADC 8 30 MS/s 18 mW 1.8 V 0.18 µm 6 50 MS/s 20 mW 1V 0.35 µm - 4 MS/s 140 µW 1V 90 µm Sigma Delta - 1.5 MS/s 40 µW 0.9 V 0.5 µm ADC - 1 MS/s 80 µW 0.7 V 0.18 µm Flash 6 1.2 GS/s 90 mW 1.5 V 0.13 µm ADC 6 1.3 GS/s 600 mW 1.8 V 0.25 µm 6 1 MS/s 7 µW 0.5 V 90 nm SAR 8 200 kS/s 2.5 µW 0.9 V 0.18 µm ADC 10 1MS/s 1.9 µW 1V 65 nm 5 250 MS/s 1.2 µW 0.8 V 65 nm 14
15. 15. Market SurveyThere are many IC companies, which make different kinds of dataconvertors. The following is list of some companies, which make dataconverters Analog Devices National Semiconductors Texas Instruments Microchip Maxim Cirrus Logic Universal Semiconductor, Inc Accord Solutions, Inc Aimtron Technology Analog Microelectronics Arizona Microtek, Inc 15
16. 16. Market SurveyTexas Instruments have announced the 16, 14, 12 bits six channel simultaneouslysampling analog to digital converter. The maximum data rate per channel isaround 500kSPS . The following data shows the detail features about six channelSAR ADC Features of six channel SAR ADCs • Family of 16, 14, 12 bits, Pin and software Compatible ADC • Six SAR ADCs Grouped in three Pairs • Maximum Data Rate Per Channel with Internal Conversion Clock and Reference: ADS8556: 630kSPS (PAR) or 450kSPS (SER) ADS8557: 670kSPS (PAR) or 470kSPS (SER) ADS8558: 730kSPS (PAR) or 500kSPS (SER) • Maximum Data Rate with External Conversion Clock and Reference: 800kSPS (PAR) or 530kSPS 16
17. 17. Market Survey• Pin Selectable or Programmable Input Voltage Ranges: Up to ±12V• Excellent Signal to Noise Performance: 91.5dB (ADC8556) 85 dB (ADS8557) 73.9 dB (ADS8558)• Programmable and Buffered Internal Reference: 0.5V to 2.5V and0.5V to 3.0V• Operating Temperature Range: -40 C to +125 C Device Uses • Power Quality Measurement • Protection Relays • Multi-Axis Motor Control • Programmable Logic Controllers • Industrial Data Acquisition 17
18. 18. Functional Diagram 18
19. 19. Market Survey ADS8556 ADS8557 ADS8558 Resolution (Bits) 16 14 12Sample Rate (max) (SPS) 630kSPS 670kSPS 730kSPS Input Range +/-1V to +/-12V +/-1V to +/-12V +/-1V to +/-12V DNL (Max) (+/-LSB) 2 1 0.5 INL (Max) (+/-LSB) 4 1 0.75 SNR (dB) 91.5 85 73.9Power Consumption (Typ) 251.7 253.2 262.2 (mW) 19
20. 20. TYPICAL CHARACTERISTICSAt +25°C, over entire supply voltage range, VREF = 2.5V (internal), andfDATA = maximum, unless otherwise noted 20
21. 21. TYPICAL CHARACTERISTICS 21
22. 22. TYPICAL CHARACTERISTICS 22
24. 24. The overall accuracy and linearity of the SARADC are determined primarily by the internalDAC’s characteristics. Early precision SAR ADCs,such as the industry-standard AD574A usedDACs with laser-trimmed thin-film resistors toachieve the desired accuracy and linearity.However, the process of depositing andtrimming thin-film resistors adds cost, and thethin-film resistor values may be affected afterthe device is subjected to the mechanicalstresses of packaging.• Resolution : 12 bit• Complete 12-Bit A/D Converter with• Reference and Clock• 8- and 16-Bit Microprocessor BusInterface• No Missing Codes Over Temperature• 35 µs Maximum Conversion Time 24
25. 25. Figure 5. Functional block diagram of a modern 1-MSPS SAR ADC with 8-channel input multiplexer. Itsfamily includes the AD79085 (8 bits), AD79186 (10bits), and AD79287 (12 bits). 25
26. 26. Precision Resolution, 14 Bits to 18 Bits Part Channel Resolution Throughpu PowerNumber Count (Bits) t (mW) (kSPS)AD7682 4 16 250 18AD7689 8 16 250 18AD7699 8 14 500 36AD7949 8 14 250 18 26
27. 27. High Speed SAR ADCsThe AD7626 is a breakthrough in dataconversion that delivers an unequaledcombination of speed and power. This 16-bitPulSAR ADC features best-in-class 15-bit ENOBand 10 MSPS throughput, which is 2.5 timesfaster than the closest competition. The abilityof the AD7626 to process information at highspeed, while preserving data integrity, is a keyrequirement of medical imaging and dataacquisition systems. Available in a compact5 mm × 5 mm LFCSP, it is 70% smaller thancompeting offerings and consumes just130 mW of power. 27
29. 29. Programmable, 14-Bit to 18-Bit Resolution, Bipolar ADCsPart Resolution Sample Max Operating Analog Input Range (V)Number (Bits) Rate Power (mW)AD7951 14 1 MSPS 100 0 to +5, 0 to +10, ±5, ±10AD7952 14 1 MSPS 100 0 to +5, 0 to +10, ±5, ±10 diffAD7610 16 250 kSPS 38 0 to +5, 0 to +10, ±5, ±10AD7612 16 750 kSPS 85 0 to +5, 0 to +10, ±5, ±10AD7631 18 250 kSPS 38 ±10 diffAD7634 18 670 kSPS 60 ±10 diff 29
30. 30. Understanding PulSAR ADC Support CircuitrySuccessive approximation register (SAR) analog-to-digital converters (ADCs) use variousnew techniques for improved resolution. Understanding how these devices work isimportant in preventing malfunction and erroneous issues. This application note discussesin general the pitfalls that occur regularly when using SAR ADCs and, more importantly,how to easily prevent them. 30
31. 31. industrial ApplicationsSAR CONVERTERS – LOW-POWER, MULTI-CHANNEL ADCs – IDEAL FOR PORTABLES 31
32. 32. industrial ApplicationsMCP3X02/4/8 ADC Key Features: Applications•10-bit and 12-bit resolution •Multi-channel Data Acquisition Portables• ±1 LSB DNL, ±1 LSB INL max. •Sensor Interface• ±1 LSB DNL, ±1 LSB INL max. •Process Control• On-chip sample and hold •Data Acquisition•SPI™ serial interface (modes 0,0 •Battery Operated Systemsand 1,1)•Single-supply specified operation:2.7V to 5.5V•Low-power CMOS technology: -500 nA standby current - 300 μAactive current at 5V, 100 ksps 32
33. 33. industrial Applications 33
34. 34. industrial ApplicationsA Successive-Approximation ADC for CMOS Image Sensors The CMOS image sensors are achieving a growing presence in todays mobile applications as the industry acknowledges the advances of the CMOS-based technology and its scaling possibilities. The roadmap recently unveiled for CMOS Image Sensor is announcing ever smaller pixels, after 1.4μm pixel pitch, demos with a pitch of 1.1μm were presented, and it also announces the future generation of pixels with 0.9μm pixel size. 34
35. 35. industrial Applications 35
36. 36. industrial Applications During the recent years, digital still cameras and mobilephone cameras have been strong market drivers for image sensor applications. As for the image sensor technology, more than 24 megapixels and smaller than 1.4-μm pixel pitch have been realized for the digital still cameras and the mobile-phone cameras, respectively. Needless to say, these technologies have to be developed without increasing die and optical sizes due to cost and portability constraints. This progress has had an important impact on sensors analog readout electronics, and, in particular, on their ADC architecture. 36
37. 37. industrial Applications Analogue output voltage versus lighting intensity in a pixel of a CMOS Image Sensor, SNR values and noise level 37
38. 38. industrial Applications Sensor block diagram 38
39. 39. industrial Applications SAR ADC architecture 39
40. 40. industrial ApplicationsEXPERIMENTAL RESULTS Timing of the proposed ADC 40
41. 41. industrial ApplicationsSimulation results of SA ADC. (a) Input signals, reference voltages and the twoFull-Scales. (b) Generated ramp over 9 bits (c) Generated ramp over 12bits (d) Transition between the two Full-Scales 41
42. 42. industrial Applications Zoomed view of the transition between the two Full-Scales 42