PIC16F753 Datasheet, PDF (143/238 Pages) Microchip Technology – 14/16-Pin, Flash-Based 8-Bit CMOS Microcontrollers

PIC16F753/HV753
16.0 OPERATIONAL AMPLIFIER
(OPA) MODULE
The Operational Amplifier (OPA) is a standard three-
terminal device requiring external feedback to operate.
The OPA module has the following features:
• External Connections to I/O Ports
• Selectable Unity Gain Bandwidth Product Option
• Low Leakage Inputs
• Factory Calibrated Input Offset Voltage
16.1 OPAxCON0 Register
The OPAxCON0 register, shown in Register 16-1,
controls the OPA module.
The OPA module is enabled by setting the OPAxEN bit
of the OPAxCON register. When enabled, the OPA
forces the output driver of the OPAxOUT pin into tri-
state to prevent contention between the driver and the
OPA output.
The OPAxUGM bit of the OPAxCON register enables
the Unity Gain Bandwidth mode (voltage follower) of
the amplifier. In Unity Gain mode, the OPAxNCH<1:0>
inputs are disabled. The default mode is normal three-
terminal operation.
Note:
When the OPA module is enabled, the
OPAxOUT pin is driven by the op amp
output, not by the PORT digital driver.
Refer to Section 22.0 “Electrical
Specifications” for the op amp output
drive capability.
16.2 Effects of a Reset
A device Reset forces all registers to their Reset state.
This disables the OPA module.
16.3 OPA Module Performance
Common AC and DC performance specifications for
the OPA module:
• Common Mode Voltage Range
• Leakage Current
• Input Offset Voltage
• Open Loop Gain
• Gain Bandwidth Product
Common mode voltage range is the specified voltage
range for the OPAx+ and OPAx- inputs, for which the
OPA module will perform within its specifications. The
OPA module is designed to operate with input voltages
between VSS and VDD. Behavior for Common mode
voltages greater than VDD or below VSS is not
guaranteed.
Leakage current is a measure of the small source or
sink currents on the OPAx+ and OPAx- inputs. To
minimize the effect of leakage currents, the effective
impedances connected to the OPAx+ and OPAx- inputs
should be kept as small as possible and equal. Input
offset voltage is a measure of the voltage difference
between the OPAx+ and OPAx- inputs in a closed loop
circuit with the OPA in its linear region. The offset
voltage will appear as a DC offset in the output equal to
the input offset voltage, multiplied by the gain of the
circuit.
The input offset voltage is also affected by the Common
mode voltage. The OPA is factory-calibrated to
minimize the input offset voltage of the module. Open
loop gain is the ratio of the output voltage to the
differential input voltage (OPAx+) - (OPAx-). The gain is
greatest at DC and falls off with frequency.
Gain Bandwidth Product or GBWP is the frequency at
which the open loop gain falls off to 0 dB. The lower
GBWP is optimized for systems requiring low-fre-
quency response and low-power consumption.
FIGURE 16-1:
OPA MODULE BLOCK DIAGRAM
OPAxNCH<1:0>
FVR_buffer1
DACx_output
OPAxIN-
FVR_buffer1
DACx_output
SLOPE_output
OPAxIN+
11
1
10
0
01
00
OPAxUGM
OPAx- _-
OPAx
OPAx+
+
11
10
OPAxEN
01
00
OPAxPCH<1:0>
OPAx_output
OPAxOUT
 2013 Microchip Technology Inc.
Preliminary
DS40001709A-page 143