PIC18F87J90-I/PT Microchip Technology, PIC18F87J90-I/PT Datasheet - Page 315

• Manufacturer Part Number: PIC18F87J90-I/PT
• Description: IC PIC MCU FLASH 128KB 80-TQFP
• Manufacturer: Microchip Technology
• Series: PIC® 18Fr

Specifications of PIC18F87J90-I/PT

• Program Memory Type: FLASH
• Program Memory Size: 128KB (64K x 16)
• Package / Case: 80-TFQFP
• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 48MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LCD, LVD, POR, PWM, WDT
• Number Of I /o: 67
• Ram Size: 3.8K x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 3.6 V
• Data Converters: A/D 12x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Processor Series: PIC18F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 3923 B
• Interface Type: AUSART, EUSART, I2C, SPI
• Maximum Clock Frequency: 48 MHz
• Number Of Programmable I/os: 67
• Number Of Timers: 4
• Operating Supply Voltage: 2.65 V to 3.6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734, 52712-325, EWPIC18
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 10 bit, 12 Channel
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AC162079 - HEADER MPLAB ICD2 18F85J90 64/80AC164323 - MODULE SKT FOR 100TQFP
• Eeprom Size: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

24.3.2
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. The measurement is then
performed using the following steps:
1.
2.
3.
4.
5.
6.
where I is known from the current source measurement
step, t is a fixed delay and V is measured by performing
an A/D conversion.
 2010 Microchip Technology Inc.
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
OFFSET
CAPACITANCE CALIBRATION
= C
STRAY
+ C
AD
= (I • t)/V
PIC18F87J90 FAMILY
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 need to be used to adjust the
time, t, that the circuit is charged to obtain a reasonable
voltage reading from the A/D Converter. The value of t
may be determined by setting C
value, then solving for t. For example, if C
theoretically calculated to be 11 pF, and V is expected
to be 70% of V
or 63 s.
See Example 24-3 for a typical routine for CTMU
capacitance calibration.
(4 pF + 11 pF) • 2.31V/0.55 A
DD
, or 2.31V, then t would be:
AD
is approximately 4 pF.
OFFSET
DS39933D-page 315
STRAY
to a theoretical
+ C
STRAY
AD
is
is