MAX1215(2005) 查看數據表（PDF） - Maxim Integrated
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MAX1215 Datasheet PDF : 20 Pages
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1.8V, 12-Bit, 250Msps ADC for
Broadband Applications
To further enhance THD and SFDR performance at high
input frequencies (>100MHz), a second transformer
(Figure 8) should be placed in series with the single-
ended-to-differential conversion transformer. This trans-
former reduces the increase of even-order harmonics at
high frequencies.
Single-Ended, AC-Coupled Analog Inputs
Although not recommended, the MAX1215 can be used
in single-ended mode (Figure 9). Analog signals can be
AC-coupled to the positive input INP through a 0.1µF
capacitor and terminated with a 49.9Ω resistor to AGND.
The negative input should be reverse terminated with
24.9Ω resistors and AC-grounded with a 0.1µF capacitor.
Grounding, Bypassing, and
Board Layout Considerations
The MAX1215 requires board layout design techniques
suitable for high-speed data converters. This ADC pro-
vides separate analog and digital power supplies. The
analog and digital supply voltage pins accept 1.7V to
1.9V input voltage ranges. Although both supply types
can be combined and supplied from one source, it is
recommended to use separate sources to cut down on
performance degradation caused by digital switching
currents, which can couple into the analog supply net-
work. Isolate analog and digital supplies (AVCC and
OVCC) where they enter the PC board with separate
networks of ferrite beads and capacitors to their corre-
sponding grounds (AGND, OGND).
SINGLE-ENDED
INPUT TERMINAL 0.1µF
ADT1-1WT
ADT1-1WT
25Ω
25Ω
0.1µF
10Ω INP
INN
10Ω
AVCC OVCC
MAX1215
D0P/N–D11P/N
12
AGND OGND
Figure 8. Analog Input Configuration with Back-to-Back Transformers and Secondary-Side Termination
SINGLE-ENDED
INPUT TERMINAL
0.1µF
INP
50Ω
0.1µF
INN
25Ω
Figure 9. Single-Ended AC-Coupled Analog Input Configuration
AVCC OVCC
MAX1215
D0P/N–D11P/N
12
AGND OGND
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