C8051F321R Silicon Laboratories Inc, C8051F321R Datasheet - Page 44

• Manufacturer Part Number: C8051F321R
• Description: IC 8051 MCU 16K FLASH 28MLP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F32xr

Specifications of C8051F321R

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: SMBus (2-Wire/I²C), SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 21
• Program Memory Size: 16KB (16K x 8)
• Program Memory Type: FLASH
• Ram Size: 2.25K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 3.6 V
• Data Converters: A/D 13x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 28-VQFN Exposed Pad, 28-HVQFN, 28-SQFN, 28-DHVQFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Other names: 336-1067-2

C8051F320/1
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 accuracy required for the conver-
sion. 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 5.4 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 VDD with
respect to GND, 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).
44
TOTAL
is the sum of the AMUX0 resistance and any external source resistance.
Px.x
Px.x
TOTAL
RC
Differential Mode
MUX Select
Input
Select
MUX
= R
reduces to R
MUX
Equation 5.1. ADC0 Settling Time Requirements
R
R
* C
MUX
MUX
Figure 5.4. ADC0 Equivalent Input Circuits
SAMPLE
= 5k
= 5k
t
MUX
=
. See Table 5.1 for ADC0 minimum settling time requirements.
C
C
ln
SAMPLE
SAMPLE


------ -
SA
2
= 5pF
= 5pF
n


×
Rev. 1.1
R
TOTAL
C
Px.x
SAMPLE
Single-Ended Mode
RC
MUX Select
Input
= R
MUX
R
* C
MUX
SAMPLE
= 5k
C
SAMPLE
= 5pF