AD7949 Analog Devices, AD7949 Datasheet - Page 14

• Manufacturer Part Number: AD7949
• Description: 14-Bit, 8-Channel, 250 kSPS PulSAR ADC
• Manufacturer: Analog Devices

Specifications of AD7949

• Resolution (bits): 14bit
• # Chan: 8
• Sample Rate: 250kSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni,SE-Uni
• Adc Architecture: SAR
• Pkg Type: CSP

AD7949
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 = V
paired differentially with INx− = V
twos complement.
The ideal transfer characteristic for the AD7949 is shown in
Figure 24 and for both unipolar and bipolar ranges with the
internal 4.096 V reference.
Table 7. Output Codes and Ideal Input Voltages
Description
FSR − 1 LSB
Midscale + 1 LSB
Midscale
Midscale − 1 LSB
−FSR + 1 LSB
−FSR
1
2
3
4
With COM or INx− = 0 V or all INx referenced to GND.
With COM or INx− = V
This is also the code for an overranged analog input ((INx+) − (INx−), or COM, above V
This is also the code for an underranged analog input ((INx+) − (INx−), or COM, below GND).
REF
/2.
Unipolar Analog Input
V
4.095750 V
2.048250 V
2.048000 V
2.047750 V
250 μV
0 V
REF
= 4.096 V
REF
/2), the data outputs are
1
Digital Output Code
(Straight Binary Hex)
0x3FFF
0x2001
0x2000
0x1FFF
0x0001
0x0000
REF
3
4
/2 or
Rev. C | Page 14 of 32
REF
− GND).
COMPLEMENT
TWOS
011...111
011...110
011...101
100...010
100...001
100...000
Bipolar Analog Input
V
2.047750 V
250 μV
0 V
−250 μV
−2.047750 V
−2.048 V
REF
= 4.096 V
STRAIGHT
111...111
111...110
111...101
000...010
000...001
000...000
BINARY
Figure 24. ADC Ideal Transfer Function
–FSR + 0.5LSB
–FSR
–FSR + 1LSB
2
ANALOG INPUT
Digital Output Code
(Twos Complement Hex)
0x1FFF
0x0001
0x0000
0x3FFF
0x2001
0x2000
+FSR – 1.5LSB
3
4
Data Sheet
+FSR – 1LSB