PIC18F4431-E/ML Microchip Technology, PIC18F4431-E/ML Datasheet - Page 251

• Manufacturer Part Number: PIC18F4431-E/ML
• Description: IC MCU FLASH 8KX16 44QFN
• Manufacturer: Microchip Technology
• Series: PIC® 18Fr

Specifications of PIC18F4431-E/ML

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LVD, Power Control PWM, QEI, POR, PWM, WDT
• Number Of I /o: 36
• Program Memory Size: 16KB (8K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 768 x 8
• Voltage - Supply (vcc/vdd): 4.2 V ~ 5.5 V
• Data Converters: A/D 9x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 44-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

21.4
If external voltage references are used instead of the
internal AV
impedance of the V
must be considered. During acquisition, currents
supplied by these sources are insignificant. However,
during conversion, the A/D module sinks and sources
current through the reference sources.
In order to maintain the A/D accuracy, the voltage
reference source impedances should be kept low to
reduce voltage changes. These voltage changes occur
as reference currents flow through the reference
source impedance.
21.5
The ADCON2 register allows the user to select an acqui-
sition time that occurs each time an A/D conversion is
triggered.
When the GO/DONE bit is set, sampling is stopped and
a conversion begins. The user is responsible for ensuring
the required acquisition time has passed between
selecting the desired input channel and the start of
conversion. This occurs when the ACQT<3:0> bits
(ADCON2<6:3>) remain in their Reset state (‘0000’).
TABLE 21-2:
 2010 Microchip Technology Inc.
Note 1:
Note:
2:
3:
4:
A/D Voltage References
Selecting and Configuring
Automatic Acquisition Time
Operation
The RC source has a typical T
The RC source has a typical T
For device frequencies above 1 MHz, the device must be in Sleep for the entire conversion or the A/D
accuracy may be out of specification unless in Single-Shot mode.
Low-power devices only.
When using external references, the
source impedance of the external voltage
references must be less than 75 in order
to achieve the specified ADC resolution. A
higher reference source impedance will
increase the ADC offset and gain errors.
Resistive voltage dividers will not provide a
low enough source impedance. To ensure
the best possible ADC performance, exter-
nal V
op amp or other low-impedance circuit.
16 T
32 T
64 T
RC/4
2 T
4 T
8 T
DD
RC
OSC
OSC
OSC
OSC
OSC
OSC
(3)
REF
AD Clock Source (T
and AV
(3)
T
AD
REF
inputs should be buffered with an
vs. DEVICE OPERATING FREQUENCIES
+ and V
SS
sources, the source
REF
- voltage sources
AD
ADCS<2:0>
)
AD
AD
000
100
001
101
010
110
011
111
time of 2-6 s.
time of 0.5-1.5 s.
PIC18F2331/2431/4331/4431
If desired, the ACQT bits can be set to select a
programmable acquisition time for the A/D module.
When triggered, the A/D module continues to sample
the input for the selected acquisition time, then
automatically
acquisition time is programmed, there may be no need
to wait for an acquisition time between selecting a
channel and triggering the A/D. If an acquisition time is
programmed, there is nothing to indicate if the
acquisition time has ended or if the conversion has
begun.
21.6
The A/D conversion time per bit is defined as T
A/D conversion requires 12 T
The source of the A/D conversion clock is software
selectable. There are eight possible options for T
For correct A/D conversions, the A/D conversion clock
(T
minimum T
A11
Table 21-2
the device operating frequencies and the A/D clock
source selected.
AD
PIC18FXX31
1.00 MHz
) must be as short as possible, but greater than the
4.0 MHz
• 2 T
• 4 T
• 8 T
• 16 T
• 32 T
• 64 T
• Internal RC Oscillator
• Internal RC Oscillator/4
for more information).
19.2 MHz
38.4 MHz
40.0 MHz
40.0 MHz
4.8 MHz
9.6 MHz
Selecting the A/D Conversion
Clock
Maximum Device Frequency
OSC
OSC
OSC
OSC
OSC
OSC
shows the resultant T
AD
(2)
(1)
(approximately 416 ns, see parameter
begins
a
conversion.
AD
PIC18LFXX31
per 10-bit conversion.
AD
1.00 MHz
10.65 MHz
21.33 MHz
4.0 MHz
1.33 MHz
2.66 MHz
5.33 MHz
DS39616D-page 251
666 kHz
times derived from
(2)
Since
(2)
(4)
AD
AD
. The
the
: