AD7682 데이터 시트보기 (PDF) - Analog Devices

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AD7682

16-Bit, 4-Channel/8-Channel, 250 kSPS PulSAR ADC

Analog Devices 

AD7682/AD7689

TRANSFER FUNCTIONS

With the inputs configured for unipolar range (single ended,

COM with ground sense, or paired differentially with INx− as

ground sense), the data output is straight binary.

With the inputs configured for bipolar range (COM = VREF/2 or

paired differentially with INx− = VREF/2), the data outputs are

twos complement.

The ideal transfer characteristic for the AD7682/AD7689 is

shown in Figure 25 and for both unipolar and bipolar ranges

with the internal 4.096 V reference.

TWOS

STRAIGHT

COMPLEMENT BINARY

011...111

011...110

011...101

111...111

111...110

111...101

100...010

100...001

100...000

000...010

000...001

000...000

–FSR

–FSR + 1LSB

–FSR + 0.5LSB

+FSR – 1LSB

+FSR – 1.5LSB

ANALOG INPUT

Figure 25. ADC Ideal Transfer Function

Table 7. Output Codes and Ideal Input Voltages

Description

Unipolar Analog Input1

VREF = 4.096 V

Digital Output Code

(Straight Binary Hex)

FSR − 1 LSB

4.095938 V

0xFFFF

Midscale + 1 LSB 2.048063 V

0x8001

Midscale

2.048 V

0x8000

Midscale − 1 LSB 2.047938 V

0x7FFF

−FSR + 1 LSB

62.5 μV

0x0001

−FSR

0V

0x0000

1 With COM or INx− = 0 V or all INx referenced to GND.

2 With COM or INx− = VREF /2.

3 This is also the code for an overranged analog input ((INx+) − (INx−), or COM, above VREF − VGND).

4 This is also the code for an underranged analog input ((INx+) − (INx−), or COM, below VGND).

Bipolar Analog Input2

VREF = 4.096 V

2.047938 V

62.5 μV

0V

−62.5 μV

−2.047938 V

−2.048 V

Digital Output Code

(Twos Complement Hex)

0x7FFF

0x0001

0x00004

0xFFFF3

0x8001

0x8000

Rev. 0 | Page 16 of 28

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