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choice of ADC

Intellectual 405 points

Replies: 14

Views: 8482

I'm using a apd5100 pressure sensor to monitor arterial line blood pressure. Since its an integrated sensor, i figured i could directly connect it to a 16 bit ADC.However I ain't sure of the choice of ADC for this application...as 1. the sampling rate 2. architecture-SAR/delta sigma 3. Input configuration range

Kindly help me out.

  • In reply to Tom Hendrick:

    any specific reason as to why u suggested this ADC? and is a voltage follower circuit necessary?

    Also, if I'm simulating the output signal of the sensor, can I do so by connecting a 5k pot across 5V and gnd and give its output directly to any ADC which then communicates with an MSP430.

  • In reply to amj:

    Hi amj,

    No specific reason for the ADS8326 other than its 'ease of use'.  Typically a SAR adc wants to see a low impedance input.  You may be able to get decent results with the 5K pot depending on your sample rate.  In another post to this forum, you are looking for an 8-bit device in a DIP package.  Here are a few:

    Part Number   Status   Resolution (Bits)   Sample Rate (max)   # Input Channels   Architecture   Input Configuration Range   Interface   Serial SPI Interface   INL (+/-) (max) (%)   INL (max) (+/-LSB)   DNL (max) (+/-LSB)   Analog Input BW (MHz)   SNR (dB)   SFDR (dB)   SINAD (dB)   ENOB (Bits)   Power Consumption (typ) (mW)   Reference Mode   Analog Voltage AV/DD (min) (V)   Analog Voltage AV/DD (max) (V)   Digital Supply (min) (V)   Digital Supply (max) (V)   Rating   Pin/Package   Approx. Price (US$)   Description  
    Pict Pict
    TLV0838
     ACTIVE  8  37.9kSPS  8  SAR   Vref   Serial SPI Interface     0.2 0.5 0.5                0.66  Ext  2.7 3.6 2.7 3.6  Catalog  20PDIP20SOIC20TSSOP  1.45 | 1ku   8-Bit 37.9 kSPS ADC Serial Out, Ratiometric Op or Vcc Ref, TTL/MOS Input & Output Compatible, 8 Ch. 
    TLV0834  ACTIVE  8  41kSPS  4  SAR   Vref   Serial SPI Interface     0.2 0.5 0.5                0.66  Ext  2.7 3.6 2.7 3.6  Catalog  14PDIP14SOIC16TSSOP  1.45 | 1ku   8-Bit 41 kSPS ADC Serial Out, Ratiometric Op or Vcc Ref, TTL/MOS Input & Output Compatible, 4 Ch. 
    TLV0832  ACTIVE  8  44.7kSPS  2  SAR   Vref   Serial SPI Interface     0.2 0.5 0.5                5  Ext  2.7 3.6 2.7 3.6  Catalog  8PDIP8SOIC  1.40 | 1ku   8-Bit 44.7 kSPS ADC Serial Out, Muxed Twin Ch. w/SE or Differential Option, 2 Ch. 
    TLV0831  ACTIVE  8  49kSPS  1  SAR   +3.6V(Vref=VDD)   Serial SPI Interface     0.2 0.5 0.5                0.66  Ext  2.7 3.6 2.7 3.6  Catalog  8PDIP8SOIC  1.75 | 1ku   8-Bit 49 kSPS ADC Serial Out, Differential input, Configurable as SE input, 1 Ch. 
    TLC548  ACTIVE  8  45.5kSPS  1  SAR   Vref   Serial SPI Interface     0.2 0.5 0.5                9  Ext  3 6 3 6  Catalog  8PDIP8SOIC  1.20 | 1ku   8-Bit, 45.5 kSPS ADC Serial Out, Low Power, Compatible to TLC540/545/1540, Single Ch. 
    TLC542  ACTIVE  8  25kSPS  11  SAR   Vref   Serial SPI Interface     0.2 0.5 0.5                6  Ext  4.75 5.25 4.75 5.25  Catalog  20PDIP20PLCC20SOIC  1.50 | 1ku   8-Bit, 25kSPS ADC Serial-Out, On-Chip 11-Ch. Analog MUX 
    TLC540  ACTIVE  8  75kSPS  11  SAR   Vref   Serial SPI Interface     0.2 0.5 0.5                6  Ext  4.75 5.5 4.75 5.5  Catalog  20PDIP20PLCC20SOIC  1.85 | 1ku   8-Bit, 75 kSPS ADC Serial-Out, On-Chip 12-Ch. Analog Mux, 11 Ch. 
    TLC0838  ACTIVE  8  20kSPS  8  SAR   Vref   Serial SPI Interface     0.2 0.4 0.4                3  Ext  4.5 5.5 4.5 5.5  Catalog  20PDIP20SOIC20TSSOP  1.45 | 1ku   8-Bit, 20 kSPS ADC Serial Out, uProcessor Periph./Standalone, Rem. Op w/Ser. Data Link, Mux option 
    TLC0834  ACTIVE  8  20kSPS  4  SAR   Vref   Serial SPI Interface     0.2 0.4 0.4                3  Ext  4.5 5.5 4.5 5.5  Catalog  14PDIP14SOIC  1.45 | 1ku   8-Bit, 20 kSPS ADC Serial Out, uProcessor Periph./Standalone, Rem. Op w/Ser. Data Link, Mux option 
    TLC0832  ACTIVE  8  22kSPS  2  SAR   Vref   Serial SPI Interface     0.2 0.4 0.4                12.5  Ext  4.5 5.5 4.5 5.5  Catalog  8PDIP8SOIC  1.40 | 1ku   8-Bit, 22 kSPS ADC Serial Out, uProcessor Periph./Standalone, Mux option w/SE or differential, 2 Ch. 
    TLC0831  ACTIVE  8  31kSPS  1  SAR   Vref   Serial SPI Interface     0.2 0.4 0.4                3  Ext  4.5 5.5 4.5 5.5  Catalog  8PDIP8SOIC  1.40 | 1ku   8-Bit, 31 kSPS ADC Serial Out, Microprocessor Peripheral/Standalone, Single Channels 

     

    Regards,

    Tom

  • In reply to Tom Hendrick:

    thanks :) do i need to give an anti aliasing filter?

  • In reply to amj:

    You always need some kind of band-limiting filter before a data converter. Sampling a signal always results in some kind of aliasing, you just need to be sure to keep the aliased signals below the noise floor of the converter. Besides, it's good practice to only use the bandwidth you really need to keep noise low, so limiting the bandwidth of the input signal is the right thing to do.

    If you're sampling at 250kSPS, and your pressure signal is a fairly low frequency, then a simple RC filter may be all you need, or you can use FilterPro to design a second-order active filter at whatever your maximum signal frequency might be (100Hz, 500Hz?). 

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