PIC18F2331-E/SP Microchip Technology, PIC18F2331-E/SP Datasheet - Page 259

• Manufacturer Part Number: PIC18F2331-E/SP
• Description: IC MCU FLASH 4KX16 28-DIP
• Manufacturer: Microchip Technology
• Series: PIC® 18Fr

Specifications of PIC18F2331-E/SP

• Core Size: 8-Bit
• Program Memory Size: 8KB (4K x 16)
• Core Processor: PIC
• Speed: 40MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LVD, Power Control PWM, QEI, POR, PWM, WDT
• Number Of I /o: 24
• 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 5x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 28-DIP (0.300", 7.62mm)
• Controller Family/series: PIC18
• No. Of I/o's: 24
• Eeprom Memory Size: 256Byte
• Ram Memory Size: 768Byte
• Cpu Speed: 40MHz
• No. Of Timers: 4
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: I3-DB18F4431 - BOARD DAUGHTER ICEPIC3AC164035 - MODULE SKT FOR 18F2X31 28SOICDVA18XP280 - DEVICE ADAPTER 18F2220 PDIP 28LD
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

20.4
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.
20.5
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
ACQT3:ACQT0 bits (ADCON2<6:3>) remain in their
Reset state (‘0000’).
TABLE 20-2:
© 2007 Microchip Technology Inc.
Note 1:
Note:
2:
3:
4:
of
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 75Ω 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
conversion.
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
This
SS
sources, the source
REF
occurs
- voltage sources
ADCS2:ADCS0
AD
)
AD
AD
when
000
100
001
101
010
110
011
111
time of 2-6 μs.
time of 0.5-1.5 μs.
PIC18F2331/2431/4331/4431
Preliminary
the
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.
20.6
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 for more information).
Table 20-2 shows the resultant T
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
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
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
DS39616C-page 257
666 kHz
times derived from
(2)
Since
(2)
(4)
AD
AD
. The
the
: