PIC18F4439-I/PT Microchip Technology, PIC18F4439-I/PT Datasheet - Page 191

• Manufacturer Part Number: PIC18F4439-I/PT
• Description: IC MCU FLASH 6KX16 EE A/D 44TQFP
• Manufacturer: Microchip Technology
• Series: PIC® 18Fr

Specifications of PIC18F4439-I/PT

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LVD, POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 12KB (6K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 640 x 8
• Voltage - Supply (vcc/vdd): 4.2 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP, 44-VQFP
• Processor Series: PIC18F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 640 B
• Interface Type: I2C, SPI, AUSART
• Maximum Clock Frequency: 40 MHz
• Number Of Programmable I/os: 32
• Number Of Timers: 16 bit
• Operating Supply Voltage: 2 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734, 52712-325, EWPIC18
• Development Tools By Supplier: DV164005, DV164136
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 8
• For Use With: 444-1001 - DEMO BOARD FOR PICMICRO MCUAC164020 - MODULE SKT PROMATEII 44TQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

19.0
In many applications, the ability to determine if the
device voltage (V
is a desirable feature. A window of operation for the
application can be created, where the application soft-
ware can do “housekeeping tasks” before the device
voltage exits the valid operating range. This can be
done using the Low Voltage Detect module.
This module is a software programmable circuitry,
where a device voltage trip point can be specified.
When the voltage of the device becomes lower then the
specified point, an interrupt flag is set. If the interrupt is
enabled, the program execution will branch to the inter-
rupt vector address and the software can then respond
to that interrupt source.
FIGURE 19-1:
The block diagram for the LVD module is shown in
Figure 19-2. A comparator uses an internally gener-
ated reference voltage as the set point. When the
selected tap output of the device voltage crosses the
set point (is lower than), the LVDIF bit is set.
Each node in the resistor divider represents a “trip
point” voltage. The “trip point” voltage is the minimum
supply voltage level at which the device can operate
before the LVD module asserts an interrupt. When the
 2002 Microchip Technology Inc.
LOW VOLTAGE DETECT
DD
V
V
) is below a specified voltage level
A
B
TYPICAL LOW VOLTAGE DETECT APPLICATION
Time
T
A
Preliminary
T
B
The Low Voltage Detect circuitry is completely under
software control. This allows the circuitry to be “turned
off” by the software, which minimizes the current
consumption for the device.
Figure 19-1 shows a possible application voltage curve
(typically for batteries). Over time, the device voltage
decreases. When the device voltage equals voltage V
the LVD logic generates an interrupt. This occurs at
time T
until the device voltage is no longer in valid operating
range, to shutdown the system. Voltage point V
minimum valid operating voltage specification. This
occurs at time T
time for shutdown.
supply voltage is equal to the trip point, the voltage
tapped off of the resistor array is equal to the 1.2V
internal reference voltage generated by the voltage
reference module. The comparator then generates an
interrupt signal setting the LVDIF bit. This voltage is
software programmable to any one of 16 values (see
Figure 19-2).
programming the LVDL3:LVDL0 bits (LVDCON<3:0>).
A
. The application software then has the time,
Legend:
V
V
A
B
= LVD trip point
= Minimum valid device
The
B
operating voltage
. The difference T
PIC18FXX39
trip
point
DS30485A-page 189
B
is
– T
selected
A
is the total
B
is the
by
A
,