MCP6S92 Microchip Technology Inc., MCP6S92 Datasheet - Page 29

• Manufacturer Part Number: MCP6S92
• Description: Single-ended, Rail-to-rail I/o, Low-gain Pga
• Manufacturer: Microchip Technology Inc.

6.4
6.4.1
Figure 6-5 shows a circuit that measures the current I
The circuit’s performance benefits from changing the
gain on the PGA. Just as a hand-held multimeter uses
different measurement ranges to obtain the best
results, this circuit makes it easy to set a high gain for
small signals and a low gain for large signals. As a
result, the required dynamic range at the PGA’s output
is less than at its input (by up to 30 dB).
FIGURE 6-5:
Current Measurement Circuit.
6.4.2
Figure 6-6 shows a circuit using a MCP6291 at a gain
of +10 in front of a MCP6S91. This shifts the overall
gain range to +10 V/V to +320 V/V (from +1 V/V to
+32 V/V).
FIGURE 6-6:
Range.
It is also easy to shift the gain range to lower gains (see
Figure 6-7). The MCP6291 acts as a unity gain buffer,
and the resistive voltage divider shifts the gain range
down to +0.1 V/V to +3.2 V/V (from +1 V/V to +32 V/V).
 2004 Microchip Technology Inc.
V
IN
I
Typical Applications
X
1.11 k
MCP6291
GAIN RANGING
SHIFTED GAIN RANGE PGA
10.0 k
R
S
Wide Dynamic Range
PGA with Higher Gain
MCP6S9X
MCP6S91
V
OUT
V
OUT
X
.
FIGURE 6-7:
Range.
6.4.3
Figure 6-8 gives a +1 V/V to +1024 V/V gain range,
which is much greater than the range for a single PGA
(+1 V/V to +32 V/V). The first PGA provides input
multiplexing capability, while the second PGA only
needs one input. These devices can be daisy-chained
(Section 5.3 “Daisy-Chain Configuration”).
FIGURE 6-8:
Range.
6.4.4
The multiple-channel PGAs (MCP6S92 and MCP6S93)
allow the user to select which sensor appears on the
output (see Figure 6-9). These devices can also change
the gain to optimize performance for each sensor.
FIGURE 6-9:
Inputs.
V
V
IN
IN
Sensor # 0
Sensor # 1
MCP6291
EXTENDED GAIN RANGE PGA
MULTIPLE SENSOR AMPLIFIER
MCP6S92
1.11 k
MCP6S91/2/3
PGA with Lower Gain
PGA with Extended Gain
PGA with Multiple Sensor
MCP6S93
10.0 k
MCP6S91
MCP6S91
DS21908A-page 29
V
OUT
V
V
OUT
OUT