EVAL-AD7689EDZ Datasheet, PDF (17/32 Pages) Analog Devices – 16-Bit, 4-Channel/8-Channel, 250 kSPS PulSAR ADC

Data Sheet
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
AD7682/AD7689
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 8. 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
0xFFFF³
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
0x0000⁴
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 − GND).}
4 _{This is also the code for an underranged analog input ((INx+) − (INx−), or COM, below GND).}
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)
0x7FFF³
0x0001
0x0000
0xFFFF
0x8001
0x8000⁴
Rev. D | Page 17 of 32