C8051F061 View Datasheet(PDF) - Silicon Laboratories
Part Name
Description
MFG CO.
'C8051F061' PDF : 328 Pages View PDF
C8051F060/1/2/3/4/5/6/7
7.2.3. Settling Time Requirements
A minimum tracking time is required before an accurate conversion can be performed. This tracking time is
determined by the AMUX2 resistance, the ADC2 sampling capacitance, any external source resistance,
and the accuracy required for the conversion. Note that in low-power tracking mode, three SAR clocks are
used for tracking at the start of every conversion. For most applications, these three SAR clocks will meet
the minimum tracking time requirements.
Figure 7.4 shows the equivalent ADC2 input circuits for both Differential and Single-ended modes. Notice
that the equivalent time constant for both input circuits is the same. The required ADC2 settling time for a
given settling accuracy (SA) may be approximated by Equation 7.1. When measuring the Temperature
Sensor output, RTOTAL reduces to RMUX. See Table 7.1 for ADC2 minimum settling time requirements.
Equation 7.1. ADC2 Settling Time Requirements
t
=
ln
S-2---A-n-
×
RTOTALCSAMPLE
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
RTOTAL is the sum of the AMUX2 resistance and any external source resistance.
n is the ADC resolution in bits (10).
Figure 7.4. ADC2 Equivalent Input Circuits
Differential Mode
MUX Select
P1.x
RMUX = 5k
RCInput= RMUX * CSAMPLE
P1.y
RMUX = 5k
MUX Select
CSAMPLE = 5pF
CSAMPLE = 5pF
Single-Ended Mode
MUX Select
P1.x
RMUX = 5k
RCInput= RMUX * CSAMPLE
CSAMPLE = 5pF
Rev. 1.2
91
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