C8051F531-IT Silicon Laboratories Inc, C8051F531-IT Datasheet - Page 60

• Manufacturer Part Number: C8051F531-IT
• Description: IC 8051 MCU 8K FLASH 20TSSOP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F53xr

Specifications of C8051F531-IT

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 16
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 5.25 V
• Data Converters: A/D 16x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 20-TSSOP
• Data Bus Width: 8 bit
• Data Ram Size: 256 B
• Interface Type: SPI, UART
• Maximum Clock Frequency: 25 MHz
• Number Of Programmable I/os: 16
• Number Of Timers: 3
• Operating Supply Voltage: 2.7 V to 5.25 V
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 12 bit, 16 Channel
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details
• Other names: 336-1393

C8051F52x/F52xA/F53x/F53xA
4.3.6. Settling Time Requirements
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 conversion.
Figure 4.6 shows the equivalent ADC0 input circuit. The required ADC0 settling time for a given settling
accuracy (SA) may be approximated by Equation 4.1. When measuring the Temperature Sensor output,
use the settling time specified in Table 2.3 on page 29. See Table 2.3 on page 29 for ADC0 minimum set-
tling 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 (12).
4.4. Selectable Gain
ADC0 on the C8051F52x/52xA/53x/53xA family of devices implements a selectable gain adjustment
option. By writing a value to the gain adjust address range, the user can select gain values between 0 and
1.016.
For example, three analog sources to be measured have full-scale outputs of 5.0 V, 4.0 V, and 3.0 V,
respectively. Each ADC measurement would ideally use the full dynamic range of the ADC with an internal
voltage reference of 1.5 V or 2.2 V (set to 2.2 V for this example). When selecting signal one (5.0 V full-
scale), a gain value of 0.44 (5 V full scale * 0.44 = 2.2 V full scale) provides a full-scale signal of 2.2 V
when the input signal is 5.0 V. Likewise, a gain value of 0.55 (4 V full scale * 0.55 = 2.2 V full scale) for the
second source and 0.73 (3 V full scale * 0.73 = 2.2 V full scale) for the third source provide full-scale ADC0
measurements when the input signal is full-scale.
Additionally, some sensors or other input sources have small part-to-part variations that must be
accounted for to achieve accurate results. In this case, the programmable gain value could be used as a
calibration value to eliminate these part-to-part variations.
60
TOTAL
is the sum of the AMUX0 resistance and any external source resistance.
Equation 4.1. ADC0 Settling Time Requirements
Figure 4.6. ADC0 Equivalent Input Circuits
Px.x
t
=
ln
R C


------ -
SA
2
M U X S elect
Inp u t
n


= R

Rev. 1.3
R
M U X
TOTAL
* C
R
M U X
S A M P L E
C
SAMPLE
C
S A M P LE