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ADS1110: What is the minimum output code when ADS1110 is used with single-ended input mode like figure 8?

Kazuya Nakai59
Guru 21115 points
Part Number: ADS1110

Hello guys,

One of my customers is using ADS1110 for their new products.

They is using ADS1110 under the following conditions.

1. Single-ended input mode like figure 8 of on page 15 of ADS1110 datasheet (Ver. SBAS276A) is used.
2. VDD=5V, GND=0V, VIN+=0V, VIN-=0V, PGA=1.

At this condition, the read out ADC code via I2C is a minus data (the data is less than 0FFFFh).

The customer has the following question about the ADC code.
Could you please give me your reply?

Q.  What is the minimum output code (the range is 0FFFFh~8000h)  in the worst case?

     I think the minimum output code is 0FF80h(0000h-0080h) because ADS1110 1LSB voltage is 62.5uV (4.096V/65536)
    and the device offset error is 8mV (Max).

    Is my understanding correct?

You reply would be much appreciated.

Best regards,

Kazuya. 

  • 0
    TI__Guru 63205 points

    Hello,

    The ADS1110 output code is based on the full +/-VREF input range and as noted below Figure 8 the output codes will only be positive for a single-ended input and half of the codes will be lost. The ideal output code for a 0V input would be 0x0000 and the ideal full-scale positive value with a +VREF input would be 0x7FFF.  Due to the non-zero offset voltage of the product, the actual code value with a 0V input may vary by up to +/-8mV or roughly +/-256 codes with a +2.048V reference. 

  • 0 in reply to Collin Wells
    Guru 21115 points

    Hello Collin,

    Thank you very much for your reply.
    The customer understood about the variation range of the minus data because of your reply.

    Thank you again and best regards,

    Kazuya.