C8051F410/1/2/3
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.
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 5.3 and Table 5.4 for ADC0 minimum set-
tling time requirements.
2
-
t
= ln
⎛
------
⎞
×
R
TOTAL
C
SAMPLE
⎝
SA
⎠
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
n
Px.x
R
MUX
= 5
kΩ
C
SAMPLE
= 12 pF
RC
Input
= R
MUX
* C
SAMPLE
Figure 5.6. ADC0 Equivalent Input Circuits
58
Rev. 1.0
SILABS [ SILICON LABORATORIES ]
