ZHCS311D May 2009 – January 2018 ADS1113 , ADS1114 , ADS1115
PRODUCTION DATA.
Table 11 shows the chosen values for this design.
PARAMETER | VALUE |
---|---|
VCM | 2.5 V |
FSR of ADC | ±0.256 V |
Output Data Rate | 250 SPS |
R1, R3 | 1 kΩ(1) |
R2, R4 | 5 kΩ(1) |
R5, R6 | 100 Ω(1) |
CDIFF | 0.22 µF |
CCM1, CCM2 | 0.022 µF |
Using Equation 7, if VSHUNT ranges from –50 mV to +50 mV, the application circuit produces a differential voltage ranging from –0.250 V to +0.250 V across the ADC inputs . The ADC is therefore configured at a FSR of ±0.256 V to maximize the dynamic range of the ADC.
The –3 dB cutoff frequencies of the differential low-pass filter and the common-mode low-pass filters are set at 3.6 kHz and 0.36 kHz, respectively.
RSHUNT typically ranges from 0.01 mΩ to 100 mΩ. Therefore, if R1 = R3 = 1 kΩ, a good trade-off exists between the circuit input impedance and input referred resistor noise as explained in the Noise and Input Impedance Considerations section.
A simple resistor divider followed by a buffer amplifier is used to generate VCM of 2.5 V from a 5-V supply.