Microchip Technology dsPIC33 series Manuel utilisateur
2014-2015 Microchip Technology Inc. DS70005146B-page 1
HIGHLIGHTS
This section of the manual contains the following major topics:
1.0 Introduction ....................................................................................................................... 2
2.0 Control Registers .............................................................................................................. 3
3.0 Module Application............................................................................................................ 6
4.0 Register Maps................................................................................................................... 9
5.0 Related Application Notes............................................................................................... 10
6.0 Revision History .............................................................................................................. 11
Programmable Gain Amplifier (PGA)
dsPIC33/PIC24 Family Reference Manual
DS70005146B-page 2 2014-2015 Microchip Technology Inc.
1.0 INTRODUCTION
The Programmable Gain Amplifier (PGA) is essentially a non-inverting amplifier with user-
programmable gains. The output of the PGA can be connected to a number of dedicated
Sample-and-Hold (S&H) inputs of the Analog-to-Digital Converter (ADC) and/or to the high-speed
analog comparator module. The PGA has five selectable gains and may be used as a ground
referenced amplifier (single-ended) or as an amplifier with an independent ground reference.
The major features of the PGA are as follows:
• Selectable operation: single-ended with internal ground or operation with independent
ground reference
• Selectable gains: 4x, 8x, 16x, 32x and 64x
• High gain bandwidth product (40 MHz)
• Rail-to-rail output voltage
• Wide input voltage range (AVSS – 0.3, AVDD + 0.3)
A simplified block diagram of the PGA module is shown in Figure 1-1.
Figure 1-1: PGAx Module Block Diagram
Note: This family reference manual section is meant to serve as a complement to device
data sheets. Depending on the device variant, this manual section may not apply to
all dsPIC33/PIC24 devices.
Please consult the note at the beginning of the “Programmable Gain Amplifier
(PGA)” chapter in the current device data sheet to check whether this document
supports the device you are using.
Device data sheets and family reference manual sections are available for
download from the Microchip Worldwide Web site at: http://www.microchip.com
GAIN<2:0> = 6 Gain of 64x
GAIN<2:0> = 5
GAIN<2:0> = 4
GAIN<2:0> = 3
GAIN<2:0> = 2
PGAx(1)
–
+
PGAx Calibration<5:0>(1)
PGAx Negative Input (1)
PGAx Positive Input (1)
Gain of 32x
Gain of 16x
Gain of 8x
Gain of 4x
PGAxOUT(1)
Note 1: x = 1 and 2.
RIN
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Programmable Gain Amplifier (PGA)
2.0 CONTROL REGISTERS
This section outlines the specific functions of each register that controls the operation of the PGA
module. The registers are as follows:
•PGAxCON: PGAx Control Register
- Enables or disables the PGA module
- Positive input selection
- Negative input selection
- Gain selection
•PGAxCAL: PGAx Calibration Register
- Stores the calibration value
Note: Each dsPIC33/PIC24 family device variant may have one or more PGA modules.
An ‘x’ used in the names of pins, control/status bits and registers denotes the
particular PGA module number. Refer to the “Programmable Gain Amplifier
(PGA)” chapter of the specific device data sheet for more details.
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Register 2-1: PGAxCON: PGAx Control Register
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
PGAEN PGAOEN SELPI2 SELPI1 SELPI0 SELNI2 SELNI1 SELNI0
bit 15 bit 8
U-0 U-0 U-0 U-0 U-0 R/W-0 R/W-0 R/W-0
— — — — — GAIN2 GAIN1 GAIN0
bit 7 bit 0
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
bit 15 PGAEN: PGAx Enable bit
1= PGAx module is enabled
0= PGAx module is disabled (reduces power consumption)
bit 14 PGAOEN: PGAx Output Enable bit
1= PGAx output is connected to the DACOUTx pin
0= PGAx output is not connected to the DACOUTx pin
bit 13-11 SELPI<2:0>: PGAx Positive Input Selection bits
111 = Reserved
110 = Reserved
101 = Reserved
100 = Reserved
011 = PGAxP4
010 = PGAxP3
001 = PGAxP2
000 = PGAxP1
bit 10-8 SELNI<2:0>: PGAx Negative Input Selection bits
111 = Reserved
110 = Reserved
101 = Reserved
100 = Reserved
011 = Ground (Single-Ended mode)
010 = PGAxN3
001 = PGAxN2
000 = Ground (Single-Ended mode)
bit 7-3 Unimplemented: Read as ‘0’
bit 2-0 GAIN<2:0>: PGAx Gain Selection bits
111 = Reserved
110 = Gain of 64x
101 = Gain of 32x
100 = Gain of 16x
011 = Gain of 8x
010 = Gain of 4x
001 = Reserved
000 = Reserved
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Programmable Gain Amplifier (PGA)
Register 2-2: PGAxCAL: PGAx Calibration Register
U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0
— — — — — — — —
bit 15 bit 8
U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
—— PGACAL<5:0>
bit 7 bit 0
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
bit 15-6 Unimplemented: Read as ‘0’
bit 5-0 PGACAL<5:0>: PGAx Offset Calibration bits
The calibration values for the PGA1 and PGA2 bits have to be copied from Flash addresses, 0x800E48
and 0x800E4C, respectively, before the module is enabled. For more information, refer to the Calibration
Data Address table in the “Special Features” chapter in the specific device data sheet.
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3.0 MODULE APPLICATION
3.1 Module Description
The Programmable Gain Amplifiers are used as voltage amplifiers; for example, amplification of
voltage across burden resistors or shunt resistors for current sensing. The Programmable Gain
Amplifiers’ output voltage can be read by any of the dedicated Sample-and-Hold circuits on the
ADC module. The PGA’s output voltage may also be used as the input to the comparator module
for overcurrent/voltage protection.
3.2 Basic Operation
The PGAx module is enabled by setting the PGAEN (PGAxCON<15>) bit to one. When the
module is disabled (PGAEN = 0), the output is placed in a high-impedance state.
The gain of the PGAx module is selectable through the GAIN<2:0> bits in the PGAxCON register.
There are five selectable gains, ranging from 4x to 64x. The SELPI<2:0> and SELNI<2:0> bits
in the PGAxCON register select one of four positive or negative inputs to the PGAx module.
For single-ended applications, the SELNI<2:0> bits will select the ground as the negative input
source. To provide an independent ground reference, the PGAxN2 and PGAxN3 pins are
available as the negative input source to the PGAx module.
The output voltage of the PGAx module can be connected to the DACOUTx pin by setting the
PGAOEN bit in the PGAxCON register. When the PGAOEN bit is enabled, the output voltage of
PGA1 is connected to DACOUT1 and PGA2 is connected to DACOUT2. For devices with a
single DACOUT pin, the output voltage of PGA2 can be connected to DACOUT1 by configuring
the DBCC bit (FDEVOPT<6>) in the Configuration register. If both the DAC output voltage and
PGA output voltage are connected to the DACOUT pin, the resulting output voltage would be a
combination of the two signals. There is no assigned priority between the PGAx module and the
DACx module.
To achieve the desired offset voltage specifications, calibration values are fed into the PGAxCAL
register. This calibration data is stored in program memory (Flash).
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Programmable Gain Amplifier (PGA)
Figure 3-1: PGAx Module Interconnection Block Diagram
Example 3-1 provides a code sequence to set up the PGA1 module with an independent ground
reference.
Example 3-1: Configuring PGA with Independent Ground Reference
Example 3-2 provides a code sequence to set up the PGA1 module in Single-Ended mode.
Example 3-2: Configuring PGA In Single-Ended Mode
Note 1: x = 1 and 2.
2: DACOUTx pin is not available on all devices, refer to the specific device data sheet for more information.
3: PGAxN3 pin is not available on all devices, refer to the specific device data sheet for more information.
–
+
PGAxP1(1)
PGAxP2(1)
PGAxP3(1)
PGAxP4(1)
SELPI<2:0>
SELNI<2:0>
GND
PGAxN2(1)
PGAxN3(1,3)
GND
ADC
S&H
PGAxCON(1) PGAxCAL(1)
PGAEN GAIN<2:0>
PGACAL<5:0>
+
–
DACx
SHxALT<1:0>
(ADALT)
ALTINP
(CMPCONx)
To DACOUTx Pin(2)
PGAx(1)
PGAOEN
CMP
PGA1CONbits.PGAEN = 0; //Disable PGA1
PGA1CONbits.SELPI = 0; //PGA1P1 as positive input
PGA1CONbits.SELNI = 1; //PGA1N2 as negative input
PGA1CONbits.GAIN = 3; //8x PGA Gain
PGA1CONbits.PGAEN = 1; //Enable PGA1
PGA1CONbits.PGAEN = 0; //Disable PGA1
PGA1CONbits.SELPI = 0; //PGA1P1 as positive input
PGA1CONbits.SELNI = 0; //Negative input is grounded
PGA1CONbits.GAIN = 2; //4x PGA Gain
PGA1CONbits.PGAEN = 1; //Enable PGA1
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Figure 3-2 illustrates an example of an SMPS application using the PGA module. In this example,
the PGA amplifies the current through the shunt resistors, with the output of the PGA connected
directly to the ADC module and the PGA configured in Single-Ended mode.
Figure 3-2: PGA Application in Interleaved PFC
IIN
IL1
ID1
ILoad
Ic
IS1
IL2
ID2
IS2
ADC
S&H PGA1
+
–
PFC Output
PWM1
PWM2
+
–
PGA2
ADC
S&H
90V-265V
Rectifier
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dsPIC33/PIC24 Family Reference Manual
4.0 REGISTER MAPS
A summary of the registers associated with the PGA module is provided in Ta b l e 4 - 1 .
Table 4-1: Programmable Gain Register Map
File Name Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 All
Resets
PGAxCON PGAEN PGAOEN SELPI2 SELPI1 SELPI0 SELNI2 SELNI1 SELNI0 — — — — — GAIN2 GAIN1 GAIN0 0000
PGAxCAL —————————— PGACAL<5:0> 0000
Legend: — = unimplemented, read as ‘0’. Reset values are shown in hexadecimal.
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5.0 RELATED APPLICATION NOTES
This section lists application notes that are related to this section of the manual. These
application notes may not be written specifically for the dsPIC33/PIC24 device families, but the
concepts are pertinent and could be used with modification and possible limitations. The current
application notes related to the PGA module are:
Title Application Note #
No related application notes are available at this time. N/A
Note: Please visit the Microchip web site (www.microchip.com) for additional application
notes and code examples for the dsPIC33/PIC24 families of devices.
Autres manuels pour dsPIC33 series
4
Ce manuel convient aux modèles suivants
1
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