PIC16F887-I/PT Microchip Technology Inc., PIC16F887-I/PT Datasheet - Page 96

• Manufacturer Part Number: PIC16F887-I/PT
• Description: MCU, 8-Bit, 8KW Flash, 368 RAM, 36 I/O, TQFP-44
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F887-I/PT

• A/d Inputs: 14-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 5 MIPS
• Eeprom Memory: 256 Bytes
• Frequency: 20 MHz
• Input Output: 35
• Interface: I2C/SPI/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 44-pin TFQP
• Programmable Memory: 14K Bytes
• Ram Size: 368 Bytes
• Resistance, Drain To Source On: Bytes
• Serial Interface: MSSP or EUSART
• Speed: 20 MHz
• Timers: 2-8-bit, 1-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIC16F882/883/884/886/887
8.10
The Comparator Voltage Reference module provides
an internally generated voltage reference for the com-
parators. The following features are available:
• Independent from Comparator operation
• Two 16-level voltage ranges
• Output clamped to V
• Ratiometric with V
• Fixed Reference (0.6V)
The VRCON register (Register 8-5) controls the
Voltage Reference module shown in Figure 8-8.
The voltage source is selectable through both ends of
the 16 connection resistor ladder network. Bit VRSS of
the VRCON register selects either the internal or
external voltage source.
The PIC16F883/884/886/887 allows the CV
to be output to the RA2 pin of PORTA under certain
configurations only. For more details, see Figure 8-9.
8.10.1
The comparator voltage reference is independent of
the comparator configuration. Setting the VREN bit of
the VRCON register will enable the voltage reference.
8.10.2
The
voltage levels in each range. Range selection is
controlled by the VRR bit of the VRCON register. The
16 levels are set with the VR<3:0> bits of the VRCON
register.
The CV
equations:
EQUATION 8-1:
The full range of V
the construction of the module. See Figure 8-8.
DS41291D-page 94
V
V
V
LADDER
RR
RR
CV
CV
CV
=
REF
=
REF
REF
REF
0 (high range):
Comparator Voltage Reference
1 (low range):
=
=
INDEPENDENT OPERATION
OUTPUT VOLTAGE SELECTION
=
output voltage is determined by the following
voltage reference has 2 ranges with 16
V
(VR<3:0>/24)
(V
DD
LADDER
SS
or ([V
DD
to V
CV
SS
/4) +
REF
DD
REF
+] - [V
×
cannot be realized due to
(VR<3:0>
V
OUTPUT VOLTAGE
LADDER
REF
-]) or V
×
V
REF
LADDER
REF
+
signal
/32)
Preliminary
8.10.3
The CV
power consumption by configuring VRCON as follows:
• VREN = 0
• VRR = 1
• VR<3:0> = 0000
This allows the comparator to detect a zero-crossing
while not consuming additional CV
8.10.4
The comparator voltage reference is V
therefore, the CV
V
Voltage Reference can be found in Section 17.0
“Electrical Specifications”.
8.10.5
The fixed voltage reference is independent of V
a nominal output voltage of 0.6V. This reference can be
enabled by setting the FVREN bit of the SRCON
register to ‘1’. This reference is always enabled when
the HFINTOSC oscillator is active.
8.10.6
When the fixed Voltage Reference module is enabled,
it will require some time for the reference and its
amplifier circuits to stabilize. The user program must
include a small delay routine to allow the module to
settle. See the electrical specifications section for the
minimum delay requirement.
8.10.7
Multiplexers on the output of the Voltage Reference
module enable selection of either the CV
voltage reference for use by the comparators.
Setting the C1VREN bit of the VRCON register enables
current to flow in the CV
the CV
bit selects the fixed voltage for use by C1.
Setting the C2VREN bit of the VRCON register enables
current to flow in the CV
the CV
bit selects the fixed voltage for use by C2.
When both the C1VREN and C2VREN bits are cleared,
current flow in the CV
minimizing the power drain of the voltage reference
peripheral.
DD
. The tested absolute accuracy of the Comparator
REF
REF
REF
voltage for use by C1. Clearing the C1VREN
voltage for use by C2. Clearing the C2VREN
OUTPUT CLAMPED TO V
OUTPUT RATIOMETRIC TO VDD
FIXED VOLTAGE REFERENCE
FIXED VOLTAGE REFERENCE
STABILIZATION PERIOD
VOLTAGE REFERENCE
SELECTION
output voltage can be set to Vss with no
REF
output changes with fluctuations in
REF
REF
REF
© 2007 Microchip Technology Inc.
voltage divider is disabled
voltage divider and selects
voltage divider and selects
REF
module current.
DD
SS
REF
derived and
DD
or fixed
, with