C8051F060_07 SILABS [Silicon Laboratories], C8051F060_07 Datasheet - Page 91

• Manufacturer Part Number: C8051F060_07
• Description: Mixed Signal ISP Flash MCU Family
• Manufacturer: SILABS [Silicon Laboratories]

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, R
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
n is the ADC resolution in bits (10).
TOTAL
is the sum of the AMUX2 resistance and any external source resistance.
P1.x
P1.y
TOTAL
RC
Differential Mode
MUX Select
MUX Select
Input
= R
reduces to R
MUX
R
R
* C
MUX
MUX
Equation 7.1. ADC2 Settling Time Requirements
SAMPLE
= 5k
= 5k
Figure 7.4. ADC2 Equivalent Input Circuits
t
=
MUX
C
C
ln
SAMPLE
SAMPLE
. See Table 7.1 for ADC2 minimum settling time requirements.


------ -
SA
2
= 5pF
= 5pF
n


×
Rev. 1.2
R
TOTAL
C8051F060/1/2/3/4/5/6/7
C
P1.x
SAMPLE
Single-Ended Mode
RC
MUX Select
Input
= R
MUX
R
* C
MUX
SAMPLE
= 5k
C
SAMPLE
= 5pF
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