PIC18F45K80-I/PT Microchip Technology, PIC18F45K80-I/PT Datasheet - Page 250

• Manufacturer Part Number: PIC18F45K80-I/PT
• Description: MCU PIC 32KB FLASH 44TQFP
• Manufacturer: Microchip Technology
• Series: PIC® XLP™ 18Fr

Specifications of PIC18F45K80-I/PT

• Core Size: 8-Bit
• Program Memory Size: 32KB (16K x 16)
• Peripherals: Brown-out Detect/Reset, LVD, POR, PWM, WDT
• Core Processor: PIC
• Speed: 64MHz
• Connectivity: ECAN, I²C, LIN, SPI, UART/USART
• Number Of I /o: 35
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 3.6K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 11x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP
• Controller Family/series: PIC18
• Ram Memory Size: 4KB
• Cpu Speed: 16MIPS
• No. Of Pwm Channels: 5
• Embedded Interface Type: I2C, SPI, USART
• Processor Series: PIC18F45K80
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 1 KB
• Interface Type: I2C, SPI, USART
• Maximum Clock Frequency: 64 MHz
• Number Of Programmable I/os: 35
• Number Of Timers: 5
• Operating Supply Voltage: 1.8 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

PIC18F66K80 FAMILY
18.4.2
There is a small amount of capacitance from the inter-
nal A/D Converter sample capacitor as well as stray
capacitance from the circuit board traces and pads that
affect the precision of capacitance measurements. A
measurement of the stray capacitance can be taken by
making sure the desired capacitance to be measured
has been removed.
After removing the capacitance to be measured:
1.
2.
3.
4.
5.
6.
Where:
• I is known from the current source measurement
• t is a fixed delay
• V is measured by performing an A/D conversion
DS39977C-page 250
step
Initialize the A/D Converter and the CTMU.
Set EDG1STAT (= 1 ).
Wait for a fixed delay of time, t .
Clear EDG1STAT.
Perform an A/D conversion.
Calculate the stray and A/D sample capacitances:
C
CAPACITANCE CALIBRATION
OFFSET
= C
STRAY
+ C
AD
= (I • t)/V
Preliminary
This measured value is then stored and used for
calculations of time measurement or subtracted for
capacitance measurement. For calibration, it is
expected that the capacitance of C
approximately known; C
An iterative process may be required to adjust the time,
t , that the circuit is charged to obtain a reasonable volt-
age reading from the A/D Converter. The value of t may
be determined by setting C
and solving for t . For example, if C
calculated to be 11 pF, and V is expected to be 70% of
V
or 63  s.
See
capacitance calibration.
DD
or 2.31V, t would be:
Example 18-3
(4 pF + 11 pF) • 2.31V/0.55 A
for a typical routine for CTMU
 2011 Microchip Technology Inc.
AD
OFFSET
is approximately 4 pF.
to a theoretical value
STRAY
STRAY
is theoretically
+ C
AD
is