Microchip Technology MCP6S22 PGA PICtail, Руководство пользователя

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MCP6S2X Evaluation Board (Rev. 4) User’s Guide
DS51327B-page 10

2004 Microchip Technology Inc.
1.3.2 Application Procedure - Program Mode
1. Place the V
DD
SELECT jumper (JP2) at the top (away from J1). The MPLAB
ICD 2 will provide 5V to the PGAs and to the microcontroller. Disconnect any
external power supply from J1.
2. Configure the MPLAB ICD 2 to provide power to the evaluation board through
the ICSP connector. This is accomplished by changing the MPLAB ICD 2
configuration in MPLAB
IDE. The MPLAB ICD 2 needs to be powered by an
external power source.
3. Connect the MPLAB ICD 2 to the ICSP connector and update the PIC16F676
firmware from a PC using MPLAB ICD 2.
4. Follow steps 3 thru 5 in 1.3.1 “Application Procedure - Stand-Alone Mode” .
1.4 HOW IT WORKS
1.4.1 PGA Functions
The PGA has an internal precision operational amplifier in a non-inverting configura-
tion. The gain of this operational amplifier is set using resistive ladders in the feedback
loop. The resistor ratio is set using analog switches that are configured according to the
instructions stored in the memory registers.
The MCP6S21/2/6/8 family of PGAs provide various input channel options: one, two,
six or eight channel inputs, respectively. The non-inverting input of the internal preci-
sion operational amplifier is directly connected to the input channels through a multi-
plexer. The multiplexer is also configured according to the command stored in the
memory registers. Figure 1-2 shows a block diagram of the MCP6S26 with six input
channels. For the single-channel MCP6S21, the non-inverting input is directly con-
nected to the input pin without a multiplexer.
FIGURE 1-2: The six-channel MCP6S26 PGA Block Diagram. The
single-channel MCP6S21 does not have an input multiplexer.
Note: The ICSP™ connector can only be used to program the PIC16F676. In
order to debug the firmware, use the MPLAB ICD 2 header. Refer to the
MPLAB ICD 2 Header Installation Information (DS51292) for more
information.
Note: Do not change either of the manual push button switches ( MCLR and
READ ) while debugging the firmware. The results of this action would be
unpredictable, and may cause damage due to conflicting voltage sources.
V
OUT
V
REF
V
DD
CS
SI
SO
SCK
CH1
CH0
CH3
CH2
CH5
CH4
V
SS
8
R
F
R
G
MUX
SPI™
Logic
POR
Gain
Switches
Res
is
tor Ladder (R
LA
D
)
MCP6S26