オーバーサンプリングによる ADC12 の高分解能 ?· jaja088 1. はじめに mcu に内蔵されるadcの分解能は、コストと性能のバランスで決定されます。より高い分解能のadcは…

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  • JAJA088- 20078

    ADC12 Harman Grewal ( ) MSP430

    (ADC) MSP430 ADC12 12bit ( Oversampling the ADC12 for Higher Resolution SLAA323 ) http://focus.ti.com/mcu/docs/mcusupporttechdocsc.tsp?sectionId=96&tabId=1502&abstractName=slaa323

    1. ........................................................................................................................................................................................ 2 2. A-D .............................................................................................................................................................. 2

    2.1.Signal-to-Noise Ratio (SN) SNR......................................................................................................................................... 2 2.2.ADC .................................................................................................................................................................... 2

    3. .............................................................................................................................................................. 4 3.1. ............................................................................................................................................................................. 4 3.2. .................................................................................................................................................................. 4

    3.2.1.100-V ................................................................................................................................................................ 4 3.2.2. ...................................................................................................................................................................... 4 3.2.3.16-bit .................................................................................................................................................... 4 3.2.4.(LPM4) ...................................................................................................................................................... 4 3.2.5................................................................................................................................................................ 4 3.2.6. ....................................................................................................................................................... 4

    4. ..................................................................................................................................................................... 5 4.1.Main()........................................................................................................................................................................................ 5 4.2.Voltage2() ................................................................................................................................................................................. 5 4.3.Temperature() .......................................................................................................................................................................... 5 4.4.Voltage() ................................................................................................................................................................................... 5 4.5.Check_cal() .............................................................................................................................................................................. 5 4.6.Temp_cal() ............................................................................................................................................................................... 5 4.7.Ref_cal() ................................................................................................................................................................................... 5

    5. ............................................................................................................................................................................................... 6 6. ............................................................................................................................................................................................... 7 7. ........................................................................................................................................................................................ 7

    1

    Texas Instruments Incorporated (TI) (TI)TITITITI

    www.tij.co.jp

    SLAA323 http://www-s.ti.com/sc/techlit/slaa323.pdf

  • JAJA088

    1. MCU ADCADCMCUADCADC

    ADC12 MSP430ADC12 200Kbps +

    2. A-D ADCLSBADCAD

    0-2500mV40V16bit 16bit LSB(1) ( 216 1 ) = ( 2.5V 0V ) 65535 = 38 V (1)

    2.1. Signal-to-Noise Ratio (SN ) SNR RMS(Root mean square)(dB)RMSADCADC(PP)(2) SNR (dB) = ( 6.02 N) 1.76 (2) N AD(2)12bit ADC74dB (2) (ENOB) ENOB+(SINAD)RMSENOB(2)SNRSINAD(+)NENOBSINADSNRFFT

    2.2. ADC ADCfs N-bit ADC 100Hz200Hz( 2100Hz) ADCENOB k = 16 100Hz 3,200Hz (k 2 100Hz) SNRSNRENOB(3)SNR N k SNR(dB) = ( 6.02 N ) 1.76 10 log10(k) (3) k = fs / (2 fmax ), fs 2 fmax

    2

  • JAJA088

    3dB 1/2 bit 16bit 12bit ADC 256 SNR

    SNR

    ADC12 3

  • JAJA088

    3.

    3.1. LCDMSP430FG439 V() ZIP R1R2 C1C2C6C7RCAVcc/DVccMCU C4C11[2]

    3.2. 250msLCDADC12250msFIR256

    3.2.1. 100-V 100-V1(SW1)

    3.2.2. 2(SW2)0.01

    3.2.3. 16-bit 3(SW3)16-bit

    3.2.4. (LPM4) 100-VSW1SW1100-VSW2SW3LCD LPM4

    3.2.5. 1. SW2 2. LCDSW2 3. LED(LCD)79FLED 4. SW1SW2 5. SW1SW2 3 6. SW1SW22 7. SW1SW21F 8. SW1SW2Step5 9.SW3

    3.2.6. 1. SW2 2. LCDSW2 3. SW3 4. LED 5. LCD 6. SW1SW2LCD(Vref)J3 10 7. SW4

    4 ADC12

  • JAJA088

    4. low_level_init init_sys LCDADC12Timer_B 390us

    4.1. Main() 250ms100-V16-bit3.2250ms LCD

    4.2. Voltage2() 100-VADC122.5V0

    4.3. Temperature() LCDADC121.5V10

    4.4. Voltage() 16-bit ADC122.5V0

    4.5. Check_cal()

    4.6. Temp_cal()

    4.7. Ref_cal() refcal

    ADC12 5

  • JAJA088

    5. 1LSBDC1-LSB16-bit DAC16-bit12-bit1 LSB2163 ZIP ( SLAA323 ) http://focus.ti.com/mcu/docs/mcusupporttechdocsc.tsp?sectionId=96&tabId=1502&abstractName=slaa323

    2()

    3()

    6 ADC12

  • JAJA088

    6. ADC12

    7 [1] MSP430FG439DAC12[2] [2]

    ADCADC12 12-bit

    7. 1.Oversampling Techniques using the TMS320C24x Family (SPRA461) 2. MSP430x4xx Family Users Guide (SLAU056) 3.Oversampling the ADC12 for Higher Resolution (SLAA323) () http://focus.ti.com/mcu/docs/mcusupporttechdocsc.tsp?sectionId=96&tabId=1502&abstractName=slaa323

    ADC12 7

  • a0193202IMPORTANT NOTICE

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