C8051F317-GMR Silicon Laboratories Inc, C8051F317-GMR Datasheet - Page 56

• Manufacturer Part Number: C8051F317-GMR
• Description: MCU 8-Bit C8051F31x 8051 CISC 16KB Flash 3.3V 24-Pin QFN EP T/R
• Manufacturer: Silicon Laboratories Inc

Specifications of C8051F317-GMR

• Package: 24QFN EP
• Device Core: 8051
• Family Name: C8051F31x
• Maximum Speed: 25 MHz
• Ram Size: 1.25 KB
• Program Memory Size: 16 KB
• Operating Supply Voltage: 3.3 V
• Data Bus Width: 8 Bit
• Program Memory Type: Flash
• Number Of Programmable I/os: 21
• Interface Type: I2C/SMBus/SPI/UART
• On-chip Adc: 17-chx10-bit
• Operating Temperature: -40 to 85 °C
• Number Of Timers: 4

C8051F310/1/2/3/4/5/6/7
5.3.3. Settling Time Requirements
When the ADC0 input configuration is changed (i.e., a different AMUX0 selection is made), 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 accu-
racy required for the conversion. 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 5.5 shows the equivalent ADC0 input circuits for both Differential and Single-ended modes. Notice
that the equivalent time constant for both input circuits is the same. 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
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
n is the ADC resolution in bits (10).
56
TOTAL
is the sum of the AMUX0 resistance and any external source resistance.
Px.x
Px.x
RC
Differential Mode
MUX Select
MUX Select
Input
DD
= R
Equation 5.1. ADC0 Settling Time Requirements
with respect to GND, R
MUX
R
R
Figure 5.5. ADC0 Equivalent Input Circuits
* C
MUX
MUX
SAMPLE
= 5k
= 5k
t
=
C
C
ln
SAMPLE
SAMPLE


------ -
SA
2
= 5pF
= 5pF
n


TOTAL

Rev. 1.7
R
TOTAL
reduces to R
C
Px.x
SAMPLE
Single-Ended Mode
RC
MUX
MUX Select
Input
= R
. See Table 5.1 for ADC0 minimum
MUX
R
* C
MUX
SAMPLE
= 5k
C
SAMPLE
= 5pF