PIC18F8520-I/PT Microchip Technology Inc., PIC18F8520-I/PT Datasheet - Page 227

• Manufacturer Part Number: PIC18F8520-I/PT
• Description: 80 PIN, 32 KB FLASH, 2048 RAM, 68 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F8520-I/PT

• A/d Inputs: 16-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 10 MIPS
• Eeprom Memory: 1024 Bytes
• Input Output: 68
• Interface: I2C/SPI/UART/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 80-pin TQFP
• Programmable Memory: 32K Bytes
• Ram Size: 2K Bytes
• Speed: 40 MHz
• Timers: 2-8-bit, 3-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part

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
An external or internal reference signal may be used,
depending on the comparator operating mode. The
analog signal present at V
at V
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.
Output
V
V
Output
IN
IN
V
V
IN
IN–
IN+
-
+
+ and the digital output of the comparator is
V
V
IN
IN
Comparator Operation
Comparator Reference
+
-
EXTERNAL REFERENCE SIGNAL
SS
and V
PIC18F6520/8520/6620/8620/6720/8720
+
–
SINGLE COMPARATOR
IN
DD
-, the output of the comparator
IN
and can be applied to either
- is compared to the signal
IN
-, the output of the
Output
IN
+ is less
IN
+ is
20.3.2
The comparator module also allows the selection of an
internally generated voltage reference for the compara-
tors. Section 21.0 “Comparator Voltage Reference
Module” contains a detailed description of the compar-
ator voltage reference module that provides this signal.
The internal reference signal is used when comparators
are in mode CM<2:0> = 110 (Figure 20-1). In this
mode, the internal voltage reference is applied to the
V
20.4
Response time is the minimum time, after selecting a
new reference voltage or input source, before the com-
parator output has a valid level. If the internal reference
is changed, the maximum delay of the internal voltage
reference must be considered when using the compar-
ator outputs. Otherwise, the maximum delay of the
comparators should be used (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 RF1 and RF2
I/O pins. When enabled, multiplexors in the output path
of the RF1 and RF2 pins will switch and the output of
each pin will be the unsynchronized output of the com-
parator. The uncertainty of each of the 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 TRISF bits will still function as an output enable/
disable for the RF1 and RF2 pins while in this mode.
The polarity of the comparator outputs can be changed
using the C2INV and C1INV bits (CMCON<4:5>).
IN
Note 1: When reading the port register, all pins
+ pin of both comparators.
2: Analog levels on any pin defined as a dig-
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.
ital input may cause the input buffer to
consume more current than is specified.
DS39609B-page 225