PIC18F2221-E/SS Microchip Technology, PIC18F2221-E/SS Datasheet - Page 245

• Manufacturer Part Number: PIC18F2221-E/SS
• Description: 4KB, Flash, 512bytes-RAM, 25I/O, 8-bit Family,nanoWatt 28 SSOP .209in TUBE
• Manufacturer: Microchip Technology
• Series: PIC® 18Fr

Specifications of PIC18F2221-E/SS

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, HLVD, POR, PWM, WDT
• Number Of I /o: 25
• Program Memory Size: 4KB (2K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 4.2 V ~ 5.5 V
• Data Converters: A/D 10x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 28-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

21.2
A single comparator is shown in Figure 21-2, along with
the relationship between the analog input levels and
the digital output. When the analog input at V
than the analog input V
is a digital low level. When the analog input at V
greater than the analog input V
comparator is a digital high level. The shaded areas of
the output of the comparator in Figure 21-2 represent
the uncertainty, due to input offsets and response time.
21.3
Depending on the comparator operating mode, either
an external or internal voltage reference may be used.
The analog signal present at V
signal at V
is adjusted accordingly (Figure 21-2).
FIGURE 21-2:
21.3.1
When external voltage references are used, the
comparator module can be configured to have the
comparators operate from the same or different
reference sources. However, threshold detector
applications may require the same reference. The
reference signal must be between V
can be applied to either pin of the comparator(s).
© 2009 Microchip Technology Inc.
V
V
Output
IN
IN
-
+
V
V
IN
IN
Comparator Operation
Comparator Reference
+
-
IN
EXTERNAL REFERENCE SIGNAL
+ and the digital output of the comparator
+
–
IN
SINGLE COMPARATOR
PIC18F2221/2321/4221/4321 FAMILY
-, the output of the comparator
IN
IN
- is compared to the
-, the output of the
SS
Output
and V
IN
+ is less
DD
IN
and
+ is
21.3.2
The comparator module also allows the selection of an
internally generated voltage reference from the
comparator voltage reference module. This module is
described in more detail in Section 22.0 “Comparator
Voltage Reference Module”.
The internal reference is only available in the mode
where four inputs are multiplexed to two comparators
(CM<2:0> = 110). In this mode, the internal voltage ref-
erence is applied to the V
21.4
Response time is the minimum time, after selecting a
new reference voltage or input source, before the
comparator output has a valid level. If the internal ref-
erence is changed, the maximum delay of the internal
voltage reference must be considered when using the
comparator outputs. Otherwise, the maximum delay of
the comparators should be used (see Section 27.0
“Electrical Characteristics”).
21.5
The comparator outputs are read through the CMCON
register. These bits are read-only. The comparator
outputs may also be directly output to the RA4 and RA5
I/O pins. When enabled, multiplexors in the output path
of the RA4 and RA5 pins will switch and the output of
each pin will be the unsynchronized output of the
comparator.
comparators is related to the input offset voltage and
the response time given in the specifications.
Figure 21-3 shows the comparator output block
diagram.
The TRISA bits will still function as an output enable/
disable for the RA4 and RA5 pins while in this mode.
The polarity of the comparator outputs can be changed
using the C2INV and C1INV bits (CMCON<5:4>).
Note 1: When reading the Port register, all pins
2: Analog levels on any pin defined as a
Comparator Response Time
Comparator Outputs
INTERNAL REFERENCE SIGNAL
configured as analog inputs will read as a
‘0’. Pins configured as digital inputs will
convert an analog input according to the
Schmitt Trigger input specification.
digital input may cause the input buffer to
consume more current than is specified.
The
uncertainty
IN
+ pin of both comparators.
of
DS39689F-page 245
each
of
the