SPRUJ53B April 2024 – September 2024 TMS320F28P550SJ , TMS320F28P559SJ-Q1
Buffered DACs are commonly used in a variety of applications such as dc-coupled applications,in which the drive amplifier must provide the required gain and offset voltage, to match the signal to the input voltage range of the ADC. As a best practice, the PGA input signal is conditioned so that the PGA output is centered within the linear range. The input signal requires some combination of offset and attenuation to achieve this goal. For example, an external resistor divider can attenuate the input signal while the embedded buffered DAC can provide a positive voltage offset, see Figure 18-11.
With the topology shown in Figure 18-11, the voltage seen at the PGA_INP pin can be calculated as:
Supplying a VDAC_OUT of 1.65V transforms a bipolar VSIGNAL range of -0.5V to +0.5V into a VPGA_INP range of 0.22V to 0.88V, which is an excellent choice for the 3˟ gain mode.
See Chapter 16 for buffered DAC usage information.