SPRUI33H November 2015 – June 2024 TMS320F280040-Q1 , TMS320F280040C-Q1 , TMS320F280041 , TMS320F280041-Q1 , TMS320F280041C , TMS320F280041C-Q1 , TMS320F280045 , TMS320F280048-Q1 , TMS320F280048C-Q1 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C-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[FILTRESSEL] register field. The default selection of PGACTL[FILTRESSEL]=0 disables the filter path.
The cutoff frequency can be estimated using the standard low-pass RC equation of:
Each gain mode requires a minimum amount of series resistance when filtering is enabled. The values are shown in Table 14-2.
Gain Mode | Minimum RFILTER |
---|---|
3x | 50 Ω |
6x | 50 Ω |
12x | 80 Ω |
24x | 100 Ω |
The choice of CFILTER value can also influence the ADC sampling performance. See Section 14.10.1.2 for more information.