C8051F52X Datasheet, PDF (48/220 Pages) Silicon Laboratories – 8/4/2 kB ISP Flash MCU Family

C8051F52x-53x
5.3.6. Settling Time Requirements
A minimum tracking time is required before an accurate conversion can be performed. This tracking time is
determined by the AMUX0 resistance, the ADC0 sampling capacitance, any external source resistance,
and the accuracy required for the conversion.
Figure 5.6 shows the equivalent ADC0 input circuit. The required ADC0 settling time for a given settling
accuracy (SA) may be approximated by Equation 5.1. When measuring the Temperature Sensor output or
V_DD with respect to GND, R_TOTAL reduces to R_MUX. See Table 5.1 and Table 5.2 for ADC0 minimum set-
tling time requirements.
t
=
ln
⎛
⎝
S^-2---A^{n--⎠⎞}
×
R_TOTALC_SAMPLE
Equation 5.1. ADC0 Settling Time Requirements
Where:
SA is the settling accuracy, given as a fraction of an LSB (for example, 0.25 to settle within 1/4 LSB)
t is the required settling time in seconds
R_TOTAL is the sum of the AMUX0 resistance and any external source resistance.
n is the ADC resolution in bits (12).
MUX Select
Px.x
R_MUX = TBD
RC_Input= R_MUX * C_SAMPLE
C_SAMPLE = TBD
Figure 5.6. ADC0 Equivalent Input Circuits
48
Rev. 0.3