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AD7292

Data Sheet

ADC TRANSFER FUNCTIONS

The output coding of the AD7292 is 10-bit straight binary for the

analog input channels. The designated code transitions occur at

successive LSB values.

To select the input range, set the appropriate bits in the VIN

RANGE1 and VIN RANGE0 subregisters of the configuration

The LSB size depends on the input range selected (see Table 9).

Table 9. Input Range and LSB Size

Input Range

LSB Size

0 V to VREF

VREF/210

0 V to 2 × VREF

2VREF/210

0 V to 4 × VREF

4VREF/210

The ideal transfer function for the AD7292 when operating

with an input range of 0 V to VREF is shown in Figure 34.

Table 10. Analog Input Range Selection

Sample with Respect to AGND

Sample with Respect to AVDD2

Subregister Bit Settings1

Single-Ended Input Range

Differential Input Range

Single-Ended Input Range

VIN RANGE1

VIN RANGE0

(VIN0 to VIN7)

(VIN0 and VIN1 Only)

(VIN0 to VIN7)

0 V to 4 × VREF

−4 × VREF to +4 × VREF

(AVDD − 4 × VREF) to AVDD

0 V to 2 × VREF

−2 × VREF to +2 × VREF

Not applicable

0 V to 2 × VREF

−2 × VREF to +2 × VREF

Not applicable

0 V to VREF

−VREF to +VREF

Not applicable

For more information, see the ADC Sampling Mode Subregister (Address 0x12) section.

The contents of the VIN RANGE0 and VIN RANGE1 subregisters are ignored when the AD7292 is configured to sample with respect to AVDD; the only input range

allowed when sampling with respect to AVDD is from (AVDD − 4 × VREF) to AVDD.

111...111

111...110

111...000

011...111

000...010

000...001

000...000

1LSB = VREF/1024

ANALOG INPUT

NOTES

1. VREF IS 1.25V.

2. INPUT RANGE IS 0V TO VREF.

+VREF – 1LSB

1LSB

Figure 34. Straight Binary Transfer Characteristic Corresponding to Single-Ended Input Range of 0 V to VREF

Table 11. Output Codes and Ideal Input Voltages (AVDD = 5 V)

Description

Analog Input Range

Digital Output

Code (Hex)

Single-Ended Mode of Operation

Differential Mode of Operation

0 V to

4 × VREF

0 V to

2 × VREF

0 V to VREF

(AVDD − 4 × VREF)

to AVDD

−4 × VREF to

+4 × VREF

−2 × VREF to

+2 × VREF

−VREF to +VREF

+FSR − 1 LSB

4.995117 V

2.497559 V

1.248779 V

4.995117 V

4.990234 V

2.495117 V

1.247559 V

0x3FF

Midscale + 1 LSB

2.504883 V

1.252441 V

0.626221 V

2.504883 V

0.009766 V

0.004883 V

0.002441 V

0x201

Midscale

2.5 V

1.25 V

0.625 V

2.5 V

0 V

0x200

Midscale − 1 LSB

2.495117 V

1.247559 V

0.623779 V

2.495117 V

−0.009766 V

−0.004883 V

−0.002441 V

0x1FF

−FSR + 1 LSB

0.004883 V

0.002441 V

0.001221 V

0.004883 V

4.995117 V

−2.495117 V

−1.247559 V

0x001

−FSR

0 V

−5 V

−2.5 V

−1.25 V

0x000

Rev. A | Page 16 of 40

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