AD9225 Analog Devices, AD9225 Datasheet - Page 11

• Manufacturer Part Number: AD9225
• Description: 12-Bit , 25 MSPS Monolithic A/D Converter
• Manufacturer: Analog Devices

Specifications of AD9225

• Resolution (bits): 12bit
• # Chan: 1
• Sample Rate: 25MSPS
• Interface: Par
• Analog Input Type: Diff-Uni,SE-Uni
• Ain Range: (2Vref) p-p,2 V p-p,4 V p-p,Uni (Vref) x 2,Uni 2.0V,Uni 4.0V
• Adc Architecture: Pipelined
• Pkg Type: SOIC,SOP

Rev. C
Input
Connection
Single-Ended
Single-Ended
Differential
(via Transformer)
or Amplifier
*VINA and VINB can be interchanged if signal inversion is required.
Reference
Operating Mode
Internal
Internal
Internal
External
(Nondynamic)
External
(Dynamic)
Coupling Span (V) VINA*
DC
AC
AC/DC
Input Span (VINA–VINB)
(V p-p)
2
4
2 £ SPAN £ 4 and
SPAN = 2
2 £ SPAN £ 4
2 £ SPAN £ 4
Input
2
2 ¥ VREF 0 to
4
2 ¥ VREF 2.0 – VREF
2 or
2 ¥ VREF 0 to 2 ¥ VREF
4
2 ¥ VREF 2.0 – VREF
2
2 ¥ VREF 2.0 – VREF/2
4.0
VREF
Table I. Analog Input Configuration Summary
Table II. Reference Configuration Summary
0 to 2
2 ¥ VREF
0 to 4
to
2.0 + VREF
0 to 1 or
0.5 to 4.5
to
2.0 + VREF
2 to 3
to
2.0 + VREF/2
1.5 to 3.5
Input Range (V)
Required VREF (V)
1
2
1 £ VREF £ 2.0 and
VREF = (1 + R1/R2)
1 £ VREF £ 2.0
CAPT and CAPB
Externally Driven
1
1 or VREF
3 to 2
VINB*
VREF
2.0
2.0
2.0
2.0
2.0 + VREF/2 12, 13
to
2.0 – VREF/2
3.5 to 1.5
–11–
Figure
No.
8, 9
8, 9
8, 9
21
10, 11
11
10
12, 13
12, 13
Connect
SENSE
SENSE
R1
R2
SENSE
VREF
SENSE
VREF
External Reference
External Reference
Comments
Best for stepped input response applications;
requires ± 5 V op amp.
Same as above but with improved noise
performance due to increase in dynamic
range. Headroom/settling time requirements
of ± 5 V op amp should be evaluated.
Optimum noise performance, excellent THD
performance, often requires low distortion op
amp with VCC > +5 V due to its headroom
issues.
Optimum THD performance with VREF = 1.
Single-supply operation (i.e., +5 V) for many
op amps.
Optimum noise performance, excellent THD
performance; ability to use ± 5 V op amp.
Flexible input range, optimum THD perfor-
mance with VREF = 1. Ability to use either
+5 V or ± 5 V op amp.
Optimum full-scale THD and SFDR perfor-
mance well beyond the ADC’s Nyquist
frequency. Preferred mode for under-
sampling applications.
Same as above with the exception that full-
scale THD and SFDR performance can be
traded off for better noise performance.
Optimum noise performance.
External Reference
To
VREF
REFCOM
VREF and SENSE
SENSE and REFCOM
AVDD
AVDD
AVSS
CAPT
CAPB
AD9225