MCP3421DM-WS View Datasheet(PDF) - Microchip Technology

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MCP3421DM-WS

MCP3421 Weight Scale Demo Board User’s Guide

Microchip Technology 

MCP3421 Weight Scale Demo Board User’s Guide

1.2 ANALOG INPUT CONFIGURATION OPTIONS

The MCP3421 Weight Scale Demo Board has an MCP6V07 auto-zeroed op amp, to

investigate different signal conditioning configuration.

As shown in Figure 1-2, the user can configure the input signal chain with the following

three options, combining the jumpers:

a) Bypassing the MCP6V07: the MCP3421 input pins are directly connected to the

sensor output. In this case, the PGA of the MCP3421 is set to a gain of 8. The

jumpers must be set as follows: J4 and J5 are on the left position. J10 and J13

are ON, while J8, J9, J11 and J12 are OFF (see Figure 1-3a).

b) Extra gain is added by the low-noise, auto-zeroed op amp MCP6V07, before the

ADC. The added gain is 50x, and the ADC’s PGA is 2x. For this option the jump-

ers must be set as follows: J4 and J5 are on the right position; J9, J11 and J12

are ON, while J8, J10 and J13 are OFF (see Figure 1-3b).

c) PGA = 1x, but uses the MCP6V07 to add high gain. Extra gain is added by the

low-noise, auto-zeroed op amp MCP6V07, before the ADC. The added gain is

250x, and the ADC’s PGA is 1x. For this option the jumpers must be set as fol-

lows: J4 and J5 are on the right position; J8, J11 and J12 are ON, while J9, J10

and J13 are OFF (see Figure 1-3c).

d) Table 1-1 shows the jumper positions and their results.

FIGURE 1-2:

Signal Conditioning and ADC on the MCP3421 Weight Scale Demo Board.

DS51918A-page 10

 2010 Microchip Technology Inc.

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