Datasheet
AD7776/AD7777/AD7778
–11–
REV. A
RTN is tied to REFOUT, then the analog input range becomes
0 V to 2 V. The fixed 2 V analog input voltage span of the ADC
can range from 1 V to 3 V (RTN = 0 V) to 0 V to 2 V (RTN =
2 V), i.e., with proper biasing, an input signal range from 0.3 V
to 2.3 V can be covered. Both the relative accuracy and differen-
tial nonlinearity performance remain essentially unchanged in
this mode, while the SNR and THD performance are typically
2 dB to 3 dB worse than standard.
Changing the Analog Input Voltage Range
By biasing the RTN pin above AGND, it is possible to change
the analog input voltage range from its V
BIAS
± V
SWING
format to
a more traditional 0 V to V
REF
range. The new input range can
be described as
VtoV REFIN
OFFSET OFFSET
+
()
where 0 V ≤ V
OFFSET
≤
1 V. To produce this range, the RTN pin
must be biased to (REFIN – 2 V
OFFSET
). For instance, if
OUTLINE DIMENSIONS
24-Lead Standard Small Outline Package [SOIC]
Wide Body
(RW-24)
Dimensions shown in millimeters and (inches)
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
COMPLIANT TO JEDEC STANDARDS MS-013AD
0.32 (0.0126)
0.23 (0.0091)
8ⴗ
0ⴗ
0.75 (0.0295)
0.25 (0.0098)
ⴛ 45ⴗ
1.27 (0.0500)
0.40 (0.0157)
SEATING
PLANE
0.30 (0.0118)
0.10 (0.0039)
0.51 (0.020)
0.33 (0.013)
2.65 (0.1043)
2.35 (0.0925)
1.27 (0.0500)
BSC
24 13
12
1
10.65 (0.4193)
10.00 (0.3937)
7.60 (0.2992)
7.40 (0.2913)
15.60 (0.6142)
15.20 (0.5984)
COPLANARITY
0.10
28-Lead Standard Small Outline Package [SOIC]
Wide Body
(RW-28)
Dimensions shown in millimeters and (inches)
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
COMPLIANT TO JEDEC STANDARDS MS-013AE
0.32 (0.0126)
0.23 (0.0091)
8ⴗ
0ⴗ
0.75 (0.0295)
0.25 (0.0098)
ⴛ 45ⴗ
1.27 (0.0500)
0.40 (0.0157)
SEATING
PLANE
0.30 (0.0118)
0.10 (0.0039)
0.51 (0.0201)
0.33 (0.0130)
2.65 (0.1043)
2.35 (0.0925)
1.27 (0.0500)
BSC
28 15
14
1
18.10 (0.7126)
17.70 (0.6969)
10.65 (0.4193)
10.00 (0.3937)
7.60 (0.2992)
7.40 (0.2913)
COPLANARITY
0.10