C8051F040DK Silicon Laboratories Inc, C8051F040DK Datasheet - Page 94

• Manufacturer Part Number: C8051F040DK
• Description: DEV KIT FOR F040/F041/F042/F043
• Manufacturer: Silicon Laboratories Inc
• Type: MCUr

Specifications of C8051F040DK

• Contents: Evaluation Board, Power Supply, USB Cables, Adapter and Documentation
• Processor To Be Evaluated: C8051F04x
• Interface Type: USB
• Silicon Manufacturer: Silicon Labs
• Core Architecture: 8051
• Silicon Core Number: C8051F040
• Silicon Family Name: C8051F04x
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: Silicon Laboratories C8051 F040, 041, 042, 043 MCUs
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 336-1205

C8051F040/1/2/3/4/5/6/7
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 ADC2 MUX resistance, the ADC2 sampling capacitance, any external source resis-
tance, and the accuracy required for the conversion. Figure 7.3 shows the equivalent ADC2 input circuit.
The required ADC2 settling time for a given settling accuracy (SA) may be approximated by Equation 7.1.
Note: An absolute minimum settling time of 0.8 µs required after any MUX selection. Note that in low-
power tracking mode, three SAR2 clocks are used for tracking at the start of every conversion. For most
applications, these three SAR2 clocks will meet the tracking 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
n is the ADC resolution in bits (8).
94
TOTAL
is the sum of the ADC2 MUX resistance and any external source resistance.
Equation 7.1. ADC2 Settling Time Requirements
Figure 7.3. ADC2 Equivalent Input Circuit
AIN2.x
t
=
RC
ln
MUX Select
Input


= R
------ -
SA
2
n
MUX


Rev. 1.5

R
* C
MUX
R
SAMPLE
TOTAL
= 5k
C
SAMPLE
C
SAMPLE
= 10pF