PIC18F4520-I/P Microchip Technology Inc., PIC18F4520-I/P Datasheet - Page 237

• Manufacturer Part Number: PIC18F4520-I/P
• Description: 40 Pin, 32 KB Flash, 1536 RAM, 36 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F4520-I/P

• A/d Inputs: 13-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 10 MIPS
• Eeprom Memory: 256 Bytes
• Input Output: 36
• Interface: I2C/SPI/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 40-pin PDIP
• Programmable Memory: 32K Bytes
• Ram Size: 1.5K Bytes
• Speed: 40 MHz
• Timers: 1-8-bit, 3-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

20.2
A single comparator is shown in Figure 20-2, 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 20-2 represent
the uncertainty, due to input offsets and response time.
20.3
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 20-2).
FIGURE 20-2:
20.3.1
When external voltage references are used, the
comparator module can be configured to have the com-
parators operate from the same or different reference
sources. However, threshold detector applications may
require the same reference. The reference signal must
be between V
pin of the comparator(s).
 2004 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
SS
and V
+
–
SINGLE COMPARATOR
IN
DD
-, the output of the comparator
and can be applied to either
IN
IN
- is compared to the
-, the output of the
Output
IN
PIC18F2420/2520/4420/4520
+ is less
IN
+ is
Preliminary
20.3.2
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 21.0 “Comparator
Voltage Reference Module”.
The internal reference is only available in the mode
where four inputs are multiplexed to two comparators
(CM2:CM0 = 110). In this mode, the internal voltage
reference is applied to the V
comparators.
20.4
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 26.0
“Electrical Characteristics”).
20.5
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 20-3 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<4:5>).
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
of
DS39631A-page 235
IN
+ pin of both
each
of
the