SPRUJ53B April 2024 – September 2024 TMS320F28P550SJ , TMS320F28P559SJ-Q1
The PGA output can be routed to a pin through an embedded series resistor for the purpose of low-pass filtering the amplified signal. The filter resistance is software selectable using the PGACTL[FILT_RES_SEL] register field. The default selection of PGACTL[FILT_RES_SEL] = 0 disables the filter path.
The cutoff frequency can be estimated using the standard low-pass RC given by:
Each gain mode requires a minimum amount of series resistance when filtering is enabled. The values are shown in Table 18-4. Also, the external capacitor value CFILTER influences the ADC sampling performance. See Section 18.10.2.2 for more information.
PGACTL[GAIN] | Minimum RFILT Required PGACTL[FILT_RES_SEL] |
---|---|
0 | 50Ω |
1 | 50Ω |
2 | 50Ω |
3 | 100Ω |
4 | 100Ω |
5 | 200Ω |
6 | 400Ω |