ZHCSN81 july 2023 ADS131B23-Q1
PRODUCTION DATA
ADC1y features an integrated programmable gain amplifier (PGA) that provides gains of 4, 8, 16, and 32. Select the gain setting using the GAIN1y[1:0] bits.
Varying the PGA gain scales the differential full-scale input voltage range (FSR) of ADC1y. Equation 9 describes the relationship between FSR and gain. Equation 9 uses the internal reference voltage, 1.25 V, as the scaling factor without accounting for gain error caused by tolerance in the reference voltage.
Table 9-8 shows the corresponding full-scale ranges for each gain setting.
GAIN SETTING | FSR |
---|---|
4 | ±312.5 mV |
8 | ±156.25 mV |
16 | ±78.125 mV |
32 | ±39.063 mV |
To measure bidirectional currents across a shunt resistor that is GND referenced, the PGA must accept voltages below GND. For that reason, the negative supply of the PGA is provided by an internal negative charge pump (NCPy). This provision allows the PGA to accept absolute input voltages on each input below GND.
The input impedance of the ADC1y channel is independent of the gain, OSR, and global-chop mode settings. The input impedance does, however, scale indirectly proportional with the MCLK frequency.