SBOU024C august 2004 – july 2023 PGA309
The PGA309 can be configured for use with an internal or external voltage reference. The reference voltage is used by the Zero DAC, Over/Under-Scale Limit, Coarse Offset Adjust DAC, Temp ADC, and Bridge Excitation Linearization Circuit. Figure 2-8 depicts the PGA309 reference circuit. If internal reference is selected, either 2.5V or 4.096V can be chosen. In this mode, a typically better than 2% initial accuracy, low drift, ±10ppm/°C reference is available for internal and external use. Up to 5mA can be supplied through the REFIN/REFOUT pin in internal reference mode. If external reference mode is chosen, then an external reference from +2.0V to +VSA may be applied to the REFIN/REFOUT pin. During power-on, the external reference mode is selected. Table 2-3 details the Register 3 bits (9:8) used for the reference mode selections.
D9 | D8 | VREF | Reference Configuration |
---|---|---|---|
RS | REN | ||
X | 0 | REFIN/REFOUT | External Reference (disable internal reference) |
0 | 1 | 4.096V | Internal Reference |
1 | 1 | 2.5V | Internal Reference |