PIC24FJ64GB002-I/SS Microchip Technology, PIC24FJ64GB002-I/SS Datasheet - Page 275

• Manufacturer Part Number: PIC24FJ64GB002-I/SS
• Description: 16-bit, 16 MIPS, 64KB Flash, 8KB RAM, Nanowatt XLP, USB OTG 28 SSOP .209in TUBE
• Manufacturer: Microchip Technology

Specifications of PIC24FJ64GB002-I/SS

• Processor Series: PIC24
• Core: PIC24F
• Data Bus Width: 16 bit
• Program Memory Type: Flash
• Program Memory Size: 64 KB
• Data Ram Size: 8192 B
• Interface Type: I2C, SPI, UART
• Maximum Clock Frequency: 32 MHz
• Number Of Programmable I/os: 21
• Number Of Timers: 5
• Operating Supply Voltage: 2 V to 3.6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SSOP-28
• Development Tools By Supplier: MPLAB Integrated Development Environment
• Minimum Operating Temperature: - 40 C
• Operating Temperature Range: - 40 C to + 85 C
• Supply Current (max): 300 mA
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

25.0
The Charge Time Measurement Unit is a flexible
analog module that provides accurate differential time
measurement between pulse sources, as well as
asynchronous pulse generation. Its key features
include:
• Four edge input trigger sources
• Polarity control for each edge source
• Control of edge sequence
• Control of response to edges
• Time measurement resolution of 1 nanosecond
• Accurate current source suitable for capacitive
Together with other on-chip analog modules, the CTMU
can be used to precisely measure time, measure
capacitance, measure relative changes in capacitance
or generate output pulses that are independent of the
system clock. The CTMU module is ideal for interfacing
with capacitive-based sensors.
The CTMU is controlled through two registers:
CTMUCON and CTMUICON. CTMUCON enables the
module and controls edge source selection, edge
source polarity selection and edge sequencing. The
CTMUICON register controls the selection and trim of
the current source.
FIGURE 25-1:
 2010 Microchip Technology Inc.
Note:
measurement
CHARGE TIME
MEASUREMENT UNIT (CTMU)
This data sheet summarizes the features
of this group of PIC24F devices. It is not
intended to be a comprehensive reference
source. For more information, refer to the
associated “PIC24F Family Reference
Manual”, Section 11. “Charge Time
Measurement Unit (CTMU)” (DS39724).
TYPICAL CONNECTIONS AND INTERNAL CONFIGURATION FOR
CAPACITANCE MEASUREMENT
C
APP
ANx
AN
R
PR
Y
PIC24FJ64GB004 FAMILY
EDG1
EDG2
PIC24F Device
A/D Converter
25.1
The CTMU module measures capacitance by generat-
ing an output pulse, with a width equal to the time
between edge events, on two separate input channels.
The pulse edge events to both input channels can be
selected from four sources: two internal peripheral
modules (OC1 and Timer1) and two external pins
(CTEDG1 and CTEDG2). This pulse is used with the
module’s precision current source to calculate
capacitance according to the relationship:
For capacitance measurements, the A/D Converter
samples an external capacitor (C
input channels after the CTMU output’s pulse. A Preci-
sion Resistor (R
on a second A/D channel. After the pulse ends, the
converter determines the voltage on the capacitor. The
actual calculation of capacitance is performed in
software by the application.
Figure 25-1 shows the external connections used for
capacitance measurements, and how the CTMU and
A/D modules are related in this application. This
example also shows the edge events coming from
Timer1, but other configurations using external edge
sources are possible. A detailed discussion on
measuring capacitance and time with the CTMU
module is provided in the “PIC24F Family Reference
Manual”.
Timer1
CTMU
Current Source
Output Pulse
Measuring Capacitance
PR
) provides current source calibration
i = C •
dV
dT
APP
DS39940D-page 275
) on one of its