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ADS1120: Can ADS1120 output 0~FFFFh when input is single end for positive signal only?

Part Number: ADS1120
Other Parts Discussed in Thread: ADS1220, ADS114S06B, ADS124S06, ADS1248, ADS1148

Hi Team, 

My customer is asking can ADS1120 output 0~FFFFh(16bit) for example, by setting registers when input is single end for positive signal only?

Or will ADS1120 only be able to output 0~7FFFh(15bit) when input is single end for positive signal only?

If so, could you recommend other device for following condition? 

1. Similar package size as ADS1120

2. more than 4 channel input

3. Be able to output 0~FFFFh(16bit) even when input is single end for positive signal only

Thanks.

Regards,

Jo

  • Jo,

    Based on your question I am assuming that the ADS1120 doesn't work for two reasons: 1) first, your customer want a single ended resolution of 16 bits with a unipolar (positive only signal), and 2) second, your customer need more channels than the ADS1120 offers.  I will assume that your customer is looking for an ADC core similar to the ADS1120.  That is, they are looking for a delta-sigma device that is optimized for low low noise DC measurement accuracy.

    1. In general, the input range for delta-sigma converters will be -Vref/Gain to +Vref/Gain.  It is very unusual to see a device where the input is true single-ended ranging from 0V to Vref.  So if the code range of 0000h to FFFFh is desired for a 0V to Vref input it may be necessary to choose a higher resolution device and truncate the data.  However, I would suggest that for small signals the PGA gain can be used to achieve a smaller LSB bit size (i.e. lower input referred noise error).  If the customer likes the ADS1120, the ADS1220 is the 24 bit equivalent device.

    2.  If the customer needs a similar device but wants more than 4 channels there are some options.  The ADS114S06B is a 6 channel devices with similar performance and package options to the ads1120.  This device input does range -Vref/Gain to +Vref/Gain so it will range 0h to 7FFFh similar to the ADS1120.  The major difference here is the extra channels.  The ADS124S06 is the 24 bit equivalent.  This device has a common analog input pin AINCOM that most other comparable devices does not have.  This pin can be connected to GND and the all mux measurements will be single ended with reference to this connection.  

    3. Another similar device is the ADS1148 (8-CH, 16 Bit, DC precision delta sigma).  The 24 bit equivalent is for this device is ADS1248. 

    Take a look at these options and let me know if you have other criteria.