MCP6S21 datasheet(26/43 Pages) MICROCHIP

26 / 43 page

MCP6S21/2/6/8

DS21117A-page 26

 2003 Microchip Technology Inc.

6.4

Typical Applications

6.4.1

GAIN RANGING

Figure 6-3 shows a circuit that measures the current IX.

It 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 6-3:

Wide Dynamic Range

Current Measurement Circuit.

6.4.2

SHIFTED GAIN RANGE PGA

Figure 6-4 shows a circuit using an MCP6021 at a gain

of +10 in front of an MCP6S21. This changes the over-

all gain range to +10 V/V to +320 V/V (from +1 V/V to

+32 V/V).

FIGURE 6-4:

PGA with Modified Gain

Range.

It is also easy to shift the gain range to lower gains (see

Figure 6-6). The MCP6021 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).

FIGURE 6-5:

PGA with lower gain range.

6.4.3

EXTENDED GAIN RANGE PGA

Figure 6-6 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 mul-

tiplexing capability, while the second PGA only needs

one input. These devices can be daisy chained

(Section 5.3, “Daisy Chain Configuration”).

FIGURE 6-6:

PGA with Extended Gain

Range.

6.4.4

MULTIPLE SENSOR AMPLIFIER

The multiple channel PGAs (except the MCP6S21)

allow the user to select which sensor appears on the

output (see Figure 6-7). These devices can also

change the gain to optimize performance for each

sensor.

FIGURE 6-7:

PGA with Multiple Sensor

Inputs.

MCP6S2X

VOUT

VIN

MCP6021

MCP6S21

VOUT

10.0 k

Ω

1.11 k

Ω

VIN

MCP6021

MCP6S21

VOUT

10.0 k

Ω

1.11 k

Ω

VIN

VOUT

MCP6S28

MCP6S21

Sensor # 0

Sensor # 1

Sensor # 5

MCP6S26

VOUT

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