PIC18F26K80-E/SP Microchip Technology Inc., PIC18F26K80-E/SP Datasheet - Page 247

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PIC18F26K80-E/SP

Manufacturer Part Number
PIC18F26K80-E/SP
Description
28 SPDIP .300IN TUBE, ECAN, 64KB FLASH, 4KB RAM, 16 MIPS, 12-BIT ADC, CTMU
Manufacturer
Microchip Technology Inc.
Datasheet

Specifications of PIC18F26K80-E/SP

A/d Inputs
8-Channel, 12-Bit
Comparators
2
Cpu Speed
16 MIPS
Eeprom Memory
256 Bytes
Input Output
24
Interface
I2C/SPI/UART/USART
Memory Type
Flash
Number Of Bits
8
Package Type
28-pin SPDIP
Programmable Memory
64K Bytes
Ram Size
3.6K Bytes
Speed
64 MHz
Temperature Range
–40 to 125 °C
Timers
2-8-bit, 3-16-bit
Voltage, Range
1.8-5.5 V
Lead Free Status / Rohs Status
RoHS Compliant part

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Part Number:
PIC18F26K80-E/SP
Manufacturer:
SILICON
Quantity:
210
The CTMU current source may be trimmed with the
trim bits in CTMUICON, using an iterative process to
get the exact current desired. Alternatively, the nominal
value without adjustment may be used. That value may
be stored by software, for use in all subsequent
capacitive or time measurements.
To calculate the optimal value for R
current must be chosen.
For example, if the A/D Converter reference voltage is
3.3V, use 70% of full scale (or 2.31V) as the desired
approximate voltage to be read by the A/D Converter. If
the range of the CTMU current source is selected to be
0.55  A, the resistor value needed is calculated as
R
if the current source is chosen to be 5.5  A, R
be 420,000 Ω, and 42,000 Ω if the current source is set
to 55  A.
FIGURE 18-2:
 2011 Microchip Technology Inc.
CAL
= 2.31V/0.55 A , for a value of 4.2 M Ω . Similarly,
ANx
R
CAL
CTMU CURRENT SOURCE
CALIBRATION CIRCUIT
Current Source
MUX
PIC18F66K80
A/D Converter
A/D
CAL
A/D
Trigger
CTMU
, the nominal
CAL
would
Preliminary
PIC18F66K80 FAMILY
A value of 70% of full-scale voltage is chosen to make
sure that the A/D Converter is in a range that is well
above the noise floor. If an exact current is chosen to
incorporate the trimming bits from CTMUICON, the
resistor value of R
ingly. R
resistor values. R
available, in light of the precision needed for the circuit
that the CTMU will be measuring. A recommended
minimum would be 0.1% tolerance.
The following examples show a typical method for
performing a CTMU current calibration.
Example 18-1
A/D Converter and the CTMU.
This routine is typical for applications using both
modules.
Example 18-2
actual calibration routine.
This method manually triggers the A/D Converter to
demonstrate the entire step-wise process. It is also
possible to automatically trigger the conversion by
setting the CTMU’s CTTRIG bit (CTMUCONH<0>).
CAL
also may be adjusted to allow for available
demonstrates how to initialize the
demonstrates one method for the
CAL
CAL
should be of the highest precision
may need to be adjusted accord-
DS39977C-page 247

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