FDC2114 datasheet(18/61 Pages) TI1

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Conversion result

Output_gain = 0x3

Output_gain = 0x2

Output_gain = 0x1

Output_gain = 0x0

(default)

MSB

LSB

Data available in DATA_MSB_CHx.DATA_CHx [11:0]

FDC2212, FDC2214, FDC2112, FDC2114

SNOSCZ5A – JUNE 2015 – REVISED JUNE 2015

www.ti.com

Figure 15. Conversion Data Output Gain

For systems in which the sensor signal variation is less than 25% of the full-scale range, the FDC can report

conversion results with higher resolution by setting the Output Gain. The Output Gain is applied to all device

channels. An output gain can be used to apply a 2-bit, 3-bit, or 4-bit shift to the output code for all channels,

allowing access to the 4 LSBs of the original 16-bit result. The MSBs of the sample are shifted out when a gain is

applied. Do not use the output gain if the MSBs of any active channel are toggling, as the MSBs for that channel

will be lost when gain is applied.

Example: If the conversion result for a channel is 0x07A3, with OUTPUT_GAIN=0x0, the reported output code is

0x07A. If OUTPUT_GAIN is set to 0x3 in the same condition, then the reported output code is 0x7A3. The

original 4 MSBs (0x0) are no longer accessible.

Table 7. Output Gain Register (FDC2112 and FDC2114 only)

EFFECTIVE

CHANNEL(1)

FIELD [ BIT(S) ]

VALUES

OUTPUT RANGE

RESOLUTION (BITS)

00 (default): Gain =1 (0 bits

100% full scale

shift)

01: Gain = 4 (2 bits left

25% full scale

shift)

RESET_DEV, addr

OUTPUT_GAIN [

All

0x1C

10:9 ]

10: Gain = 8 (3 bits left

12.5% full scale

shift)

11 : Gain = 16 (4 bits left

6.25% full scale

shift)

(1)

Channels 2 and 3 are available for FDC2114 only.

An offset value may be subtracted from each DATA value to compensate for a frequency offset or maximize the

dynamic range of the sample data. The offset values should be < fSENSORx_MIN / fREFx. Otherwise, the offset might

be so large that it masks the LSBs which are changing.

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