out the range. Thus, every input code width (quantum) must
have a finite width. If an input quantum has a value of zero
(a differential linearity error of –1LSB), a missing code will
occur.
DISCUSSION OF
SPECIFICATIONS
LINEARITY ERROR
ADC574AKP, KN, KH and TH grades are guaranteed to
have no missing codes to 12-bit resolution over their re-
spective specification temperature ranges.
Linearity error is defined as the deviation of actual code
transition values from the ideal transition values. Ideal
transition values lie on a line drawn through zero (or minus
full scale for bipolar operation) and plus full scale. The zero
value is located at an analog input value 1/2LSB before the
first code transition (000H to 001H). The full-scale value is
located at an analog value 3/2LSB beyond the last code
transition (FFEH to FFFH) (see Figure 1).
UNIPOLAR OFFSET ERROR
An ADC574A connected for unipolar operation has an
analog input range of 0V to plus full scale. The first output
code transition should occur at an analog input value 1/2
LSB above 0V. Unipolar offset error is defined as the
deviation of the actual transition value from the ideal value.
The unipolar offset temperature coefficient specifies the
change of this transition value versus a change in ambient
temperature.
Full-Scale
Calibration
FFFH
Error
Rotates
FFEH
The
Line
FFDH
802H
801H
800H
7FFH
7FEH
BIPOLAR OFFSET ERROR
A/D converter specifications have historically defined bipo-
lar offset as the first transition value above the minus full-
scale value. The ADC574A specification, however, follows
the terminology defined for the 574 converter several years
ago. Thus, bipolar offset is located near the midscale value
of 0V (bipolar zero) at the output code transition 7FFH to
800H.
Offset
Error
Shifts
The Line
002H
001H
000H
(Bipolar
Offset
Transaction)
Midscale
(Bipolar
Zero)
Bipolar offset error for the ADC574A is defined as the
deviation of the actual transition value from the ideal
transition value located 1/2LSB below 0V. The bipolar
offset temperature coefficient specifies the maximum change
of the code transition value versus a change in ambient
temperature.
3/2LSB
+Full-Scale Scale
Calibration
+Full
1/2LSB
Zero
(–Full Scale)
Zero
1/2LSB
(–Full-Scale
Calibration
Transition)
Transition
Analog Input
FIGURE 1. ADC574A Transfer Characteristics Terminology.
FULL SCALE CALIBRATION ERROR
The last output transition (FFEH to FFFH) occurs for an
analog input value 3/2LSB below the nominal full-scale
value. The full-scale calibration error is the deviation of the
actual analog value at the last transition point from the ideal
value. The full-scale calibration temperature coefficient
specifies the maximum change of the code transition value
versus a change in ambient temperature.
Thus, for a converter connected for biopolar operation and
with a full-scale range (or span) of 20V (±10V), the zero
value of –10V is 2.44mV below the first code transition
(000H to 001H at –9.99756V) and the plus full-scale value of
+10V is 7.32mV above the last code transition (FFEH to
FFFH at +9.99268) (see Table I).
NO MISSING CODES
(DIFFERENTIAL LINEARITY ERROR)
POWER SUPPLY SENSITIVITY
A specification which guarantees no missing codes requires
that every code combination to appear in a monotonically-
increasing sequence as the analog input is increased through-
Electrical specifications for the ADC574A assume the
application of the rated power supply voltages of +5V and
±12V or ±15V. The major effect of power supply voltage
BINARY (BIN) OUTPUT
INPUT VOLTAGE RANGE AND LSB VALUES
Analog Input Voltage Range
Defined as:
±10V
±5V
0 to +10V
0 to +20V
One Least Significant Bit (LSB)
FSR
2n
20V
2n
10V
2n
10V
2n
20V
2n
n = 8
n =12
78.13mV
4.88mV
39.06mV
2.44mV
39.06mV
2.44mV
78.13mV
4.88mV
Output Transition Values
FFEH to FFFH
7FFH to 800H
+Full-Scale Calibration
Midscale Calibration (Bipolar Offset)
+10V – 3/2LSB
0 – 1/2LSB
+5 – 3/2LSB
0 – 1/2LSB
+10V – 3/2LSB
+5V – 1/2LSB
+10V – 3/2LSB
±10V – 1/2LSB
TABLE I. Input Voltages, Transition Values, and LSB Values.
5
®
ADC574A
BB [ BURR-BROWN CORPORATION ]
