How close to the negative rail should the PGA309 be able to output? I am only able to get within 0.3 volts of ground.
Hello Lori,
The PGA309 can swing to 0.1V above GND and 0.1V below the VSA supply with a 10kOhm load resistor per the datasheet specification.
However the PGA309 device has also an output over-scale / under-scale function that can be enabled to limit the output swing of the device under a fault condition.
Figure 2-18 of the PGA309 user guide shows a block diagram of this function.
The Under Scale Threshold Selections are controlled by (Register 5 Bits [2:0]). Table 2-19 of the PGA309 user guide provides the threshold selections when VREF=5V.
Section 1.10 and section 2.9 of the PGA309 user guide provide a detailed explanation.
Please let me know if you have any questions.
Luis Chioye
