PIC18F46J50-I/PT Microchip Technology, PIC18F46J50-I/PT Datasheet - Page 400

• Manufacturer Part Number: PIC18F46J50-I/PT
• Description: IC PIC MCU FLASH 64KB 44-TQFP
• Manufacturer: Microchip Technology
• Series: PIC® XLP™ 18Fr

Specifications of PIC18F46J50-I/PT

• Core Size: 8-Bit
• Program Memory Size: 64KB (32K x 16)
• Core Processor: PIC
• Speed: 48MHz
• Connectivity: I²C, SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, DMA, POR, PWM, WDT
• Number Of I /o: 34
• Program Memory Type: FLASH
• Ram Size: 3.8K x 8
• Voltage - Supply (vcc/vdd): 2.15 V ~ 3.6 V
• Data Converters: A/D 13x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP, 44-VQFP
• Controller Family/series: PIC18
• No. Of I/o's: 22
• Ram Memory Size: 3.6875KB
• Cpu Speed: 48MHz
• No. Of Timers: 2
• No. Of Pwm Channels: 2
• Package: 44TQFP
• Device Core: PIC
• Family Name: PIC18
• Maximum Speed: 48 MHz
• Operating Supply Voltage: 2.5|3.3 V
• Data Bus Width: 8 Bit
• Interface Type: I2C/SPI/USART/USB
• On-chip Adc: 13-chx10-bit
• Number Of Timers: 5
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AC164330 - MODULE SKT FOR 44TQFP 18F45J10
• Eeprom Size: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

PIC18F46J50 FAMILY
The CTMU current source may be trimmed with the
trim bits in CTMUICON using an iterative process to get
an exact desired current. Alternatively, the nominal
value without adjustment may be used; it may be
stored by the software for use in all subsequent
capacitive or time measurements.
To calculate the value for R
must be chosen, and then the resistance can be
calculated. 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 μA, the resistor value needed is cal-
culated as R
Similarly, if the current source is chosen to be 5.5 μA,
R
source is set to 55 μA.
FIGURE 25-2:
DS39931C-page 400
CAL
would be 420,000Ω, and 42,000Ω if the current
ANx
R
CAL
CAL
= 2.31V/0.55 μA, for a value of 4.2 MΩ.
CTMU CURRENT SOURCE
CALIBRATION CIRCUIT
Current Source
MUX
PIC18F46J50 Device
CAL
A/D Converter
, the nominal current
A/D
CTMU
A value of 70% of full-scale voltage is chosen to make
sure that the A/D Converter was in a range that is well
above the noise floor. Keep in mind that if an exact cur-
rent is chosen that is to incorporate the trimming bits
from CTMUICON, the resistor value of R
to be adjusted accordingly. R
to allow for available resistor values. R
the highest precision available, keeping in mind the
amount of precision needed for the circuit that the
CTMU will be used to measure. A recommended
minimum would be 0.1% tolerance.
The following examples show one typical method for
performing a CTMU current calibration. Example 25-1
demonstrates how to initialize the A/D Converter and
the CTMU; this routine is typical for applications using
both modules. Example 25-2 demonstrates one
method for the actual calibration routine.
© 2009 Microchip Technology Inc.
CAL
may also be adjusted
CAL
CAL
should be of
may need