MCP6S21 N/A, MCP6S21 Datasheet - Page 27

• Manufacturer Part Number: MCP6S21
• Description: Single-Ended, Rail-to-Rail I-O, Low Gain PGA
• Manufacturer: N/A

6.4.5
Figure 6-8 shows cascaded MCP6S28s that provide
up to 15 input channels. Obviously, Sensors #7-14
have a high total gain range available, as explained in
Section 6.4.3, “Extended Gain Range”. These devices
can be daisy chained (Section 5.3, “Daisy Chain
Configuration”).
FIGURE 6-8:
6.4.6
Figure 6-9 shows an MCP6S28 driving an analog input
to a PICmicro
the input capacity of the microcontroller, while adding
the ability to select the appropriate gain for each
source.
FIGURE 6-9:
PICmicro Microcontroller.
Sensors
Sensors
# 7-14
2003 Microchip Technology Inc.
# 0-6
V
IN
EXPANDED INPUT PGA
PICmicro
INPUT CAPABILITY
®
MCP6S28
MCP6S28
microcontroller. This greatly expands
®
PGA with Expanded Inputs.
Expanded Input for a
MCU WITH EXPANDED
SPI™
MCP6S28
Microcontroller
PICmicro
®
V
OUT
6.4.7
The family of PGA’s is well suited for driving Analog-to-
Digital Converters (ADC). The binary gains (1, 2, 4, 8,
16 and 32) effectively add five more bits to the input
range (see Figure 6-10). This works well for applica-
tions needing relative accuracy more than absolute
accuracy (e.g., power monitoring).
FIGURE 6-10:
At low gains, the ADC’s Signal-to-Noise Ratio (SNR)
will dominate since the PGAs input noise voltage den-
sity is so low (10 nV/ Hz @ 10 kHz, typ.). At high gains,
the PGA’s noise will dominate the SNR, but its low
noise supports most applications. Again, these PGAs
add the flexibility of selecting the best gain for an
application.
The low pass filter in the block diagram reduces the
integrated noise at the MCP6S28’s output and serves
as an anti-aliasing filter. This filter may be designed
using Microchip’s FilterLab
www.microchip.com.
V
IN
MCP6S28
ADC DRIVER
MCP6S21/2/6/8
PGA as an ADC Driver.
Lowpass
Filter
®
software, available at
MCP3201
DS21117A-page 27
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