JAJSDU5A August 2017 – February 2020 ADS114S06B , ADS114S08B
PRODUCTION DATA.
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As with many amplifiers, the PGA has an absolute input voltage range requirement that cannot be exceeded. The maximum and minimum absolute input voltages are limited by the voltage swing capability of the PGA output. The specified minimum and maximum absolute input voltages (VAINP and VAINN) depend on the PGA gain, the maximum differential input voltage (VINMAX), and the tolerance of the analog power-supply voltages (AVDD and AVSS). Use the maximum voltage expected in the application for VINMAX. As shown in Equation 5, the absolute positive and negative input voltages must be within the specified range:
where
As mentioned in the previous section, PGA gain settings of 64 and 128 are scaled in the digital domain and are not implemented with the amplifier. When using the PGA in gains of 64 and 128, set the gain in Equation 5 to 32 to calculate the absolute input voltage range.
Figure 44 graphically shows the relationship between the PGA input to the PGA output. The PGA output voltages (VOUTP, VOUTN) depend on the PGA gain and the input voltage magnitudes. For linear operation, the PGA output voltages must not exceed AVDD – 0.15 V or AVSS + 0.15 V. The diagram depicts a positive differential input voltage that results in a positive differential output voltage.
Download the ADS1x4S0x design calculator from www.ti.com. This calculator can be used to determine the input voltage range of the PGA.