PIC18F4550-I/PT Microchip Technology Inc., PIC18F4550-I/PT Datasheet - Page 277

• Manufacturer Part Number: PIC18F4550-I/PT
• Description: 44 PIN, 32 KB FLASH, 2048 RAM, FS-USB 2.0
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F4550-I/PT

• A/d Inputs: 13-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 12 MIPS
• Eeprom Memory: 256 Bytes
• Input Output: 34
• Interface: I2C/SPI/UART/USART/USB
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 44-pin TQFP
• Programmable Memory: 32K Bytes
• Ram Size: 2K Bytes
• Speed: 48 MHz
• Timers: 1-8-bit, 3-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

23.0
The comparator voltage reference is a 16-tap resistor
ladder network that provides a selectable reference
voltage. Although its primary purpose is to provide a
reference for the analog comparators, it may also be
used independently of them.
A block diagram of the module is shown in Figure 23-1.
The resistor ladder is segmented to provide two ranges
of CV
conserve power when the reference is not being used.
The module’s supply reference can be provided from
either device V
23.1
The voltage reference module is controlled through the
CVRCON register (Register 23-1). The comparator
voltage reference provides two ranges of output
voltage, each with 16 distinct levels. The range to be
REGISTER 23-1:
© 2006 Microchip Technology Inc.
bit 7
Legend:
R = Readable bit
-n = Value at POR
bit 7
bit 6
bit 5
bit 4
bit 3-0
Note 1:
CVREN
R/W-0
REF
COMPARATOR VOLTAGE
REFERENCE MODULE
Configuring the Comparator
Voltage Reference
values and has a power-down function to
CVROE overrides the TRISA<2> bit setting.
DD
CVREN: Comparator Voltage Reference Enable bit
1 = CV
0 = CV
CVROE: Comparator V
1 = CV
0 = CV
CVRR: Comparator V
1 = 0 to 0.667 CV
0 = 0.25 CV
CVRSS: Comparator V
1 = Comparator reference source, CV
0 = Comparator reference source, CV
CVR3:CVR0: Comparator V
When CVRR = 1:
CV
When CVRR = 0:
CV
/V
CVROE
SS
REF
REF
R/W-0
or an external voltage reference.
CVRCON: COMPARATOR VOLTAGE REFERENCE CONTROL REGISTER
= ((CVR3:CVR0)/24) (CV
= (CV
REF
REF
REF
REF
(1)
circuit powered on
circuit powered down
voltage level is also output on the RA2/AN2/V
voltage is disconnected from the RA2/AN2/V
RSRC
RSRC
W = Writable bit
‘1’ = Bit is set
R/W-0
CVRR
/4) + ((CVR3:CVR0)/32) (CV
RSRC
to 0.75 CV
REF
REF
REF
, with CV
Range Selection bit
Source Selection bit
Output Enable bit
REF
PIC18F2455/2550/4455/4550
RSRC
CVRSS
R/W-0
RSRC
Value Selection bits (0
, with CV
RSRC
Preliminary
/24 step size (low range)
RSRC
RSRC
)
RSRC
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
= (V
= V
(1)
R/W-0
CVR3
used is selected by the CVRR bit (CVRCON<5>). The
primary difference between the ranges is the size of the
steps
(CVR3:CVR0), with one range offering finer resolution.
The equations used to calculate the output of the
comparator voltage reference are as follows:
The comparator reference supply voltage can come
from either V
V
voltage source is selected by the CVRSS bit
(CVRCON<4>).
The settling time of the comparator voltage reference
must be considered when changing the CV
Characteristics”).
output (see Table 28-3 in Section 28.0 “Electrical
DD
/32 step size (high range)
REF
REF
RSRC
– V
If CVRR = 1:
CV
If CVRR = 0:
CV
CV
- that are multiplexed with RA2 and RA3. The
+) – (V
)
SS
REF
REF
RSRC
selected
REF
(CVR3:CVR0)
REF
= ((CVR3:CVR0)/24) x CV
REF
= (CV
)
-/CV
DD
-/CV
R/W-0
CVR2
-)
and V
REF
REF
RSRC
by
pin
pin
SS
/4) + (((CVR3:CVR0)/32) x
the
, or the external V
x = Bit is unknown
15)
R/W-0
CVR1
CV
REF
DS39632C-page 275
RSRC
Selection
R/W-0
CVR0
REF
+ and
bit 0
REF
bits