To sample a bipolar signal and translate the sample to a range designed for downstream ADC and CMPSS modules, A combination of the PGA and DAC modules can be employed. Another use case for this mode is a Hall effect sensor that senses the total current flowing in a circuit. The Hall effect sensor has an inbuilt offset, and the range is different than what ADC can measure. Hence, a voltage conditioning circuit is needed. As an example, while the PGA works in non-inverting mode, the PGA can help to translate an input signal of –1V to 2V to an output voltage of 0.05V to 3.3V. The signal conditioning circuit is shown in Figure 2-10. The reference voltage can be generated using an embedded buffered DAC. Even though Type-1 PGA supports the non-inverting mode, using Type-2 PGA helps save a pin to use for other functions, such as ADC pin and digital inputs and outputs (AGPIO).

Figure 2-10 Signal Conditioning for a Bipolar Signal Using Non-inverting Mode

Assuming that the divider resisters R_ea=R_ia and R_eb=R_ib, the relationship between the output voltage V_{PGA_OUT}, reference voltage V_REF, and input signal V_signal is given by Equation 7.

The equation implies that the circuit can be used to translate a negative sensor output voltage to a usable ADC input voltage range, in which PGA is employed in non-inverting mode.

The following code snippet shows where to add custom code to adjust the gain value using the internal gain resistors R_ia and R_ib, as well as selecting the appropriate filter resistor R_FILT connected internally to the output of the PGA module.

//
// Gain
//
#define PGA_GAINVALUE PGA_GAIN_4

//
// Filter Resistor
//
#define PGA_FILTERVALUE PGA_LOW_PASS_FILTER_RESISTOR_800_OHM

//
// P-MUX selection
//
#define PGA_PMUXINPUT PGA_PMUX_POS 

//
// N-MUX selection
//
#define PGA_NMUXINPUT PGA_NMUX_RTAP

//
// M-MUX selection
//
#define PGA_MMUXINPUT PGA_MMUX_INVERTING_GAIN_NEG

In the code snippet, PGA_GAINVALUE represents the desired gain value for the PGA module, and PGA_FILTERVALUE represents the desired value for the filter resistor R_FILT. Please make sure to consult the documentation or reference manual for your specific device to find the available R_FILT and gain values, and then replace PGA_GAINVALUE and PGA_FILTERVALUE with the actual values you want to use in your circuit.