MCP6S92 datasheet(29/40 Pages) MICROCHIP

29 / 40 page

 2004 Microchip Technology Inc.

DS21908A-page 29

MCP6S91/2/3

6.4

Typical Applications

6.4.1

GAIN RANGING

Figure 6-5 shows a circuit that measures the current IX.

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:

Wide Dynamic Range

Current Measurement Circuit.

6.4.2

SHIFTED GAIN RANGE PGA

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:

PGA with Higher Gain

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).

FIGURE 6-7:

PGA with Lower Gain

Range.

6.4.3

EXTENDED GAIN RANGE PGA

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:

PGA with Extended Gain

Range.

6.4.4

MULTIPLE SENSOR AMPLIFIER

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:

PGA with Multiple Sensor

Inputs.

VOUT

MCP6S9X

VIN

VOUT

MCP6291

MCP6S91

1.11 k

Ω

10.0 k

Ω

VIN

MCP6291

1.11 k

Ω

10.0 k

Ω

VOUT

MCP6S91

VIN

VOUT

MCP6S92

MCP6S91

Sensor # 0

VOUT

MCP6S93

Sensor # 1

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