MAX12559 Datasheet, PDF (23/30 Pages) Maxim Integrated Products – Dual, 96Msps, 14-Bit, IF/Baseband ADC

Dual, 96Msps, 14-Bit, IF/Baseband ADC
0.1μF
V_IN
1
6
T1
N.C. ⁵
2 _N.C.
3
4
MINI-CIRCUITS
ADT1-1WT
0Ω*
75Ω
1
6
T2
0.5%
N.C. ⁵
2 _N.C.
75Ω
3
4
0.5%
MINI-CIRCUITS
ADT1-1WT
C_IN
110Ω
0.5%
R_IN
0.1μF
110Ω
0.5%
0Ω*
C_IN
*0Ω RESISTORS CAN BE REPLACED WITH
LOW-VALUE RESISTORS TO LIMIT THE INPUT BANDWIDTH. _RIN
IN_P
MAX12559
COM_
IN_N
Figure 10. Transformer-Coupled Input Drive for Input Frequencies Beyond Nyquist
Unbuffered External Reference Drives
Multiple ADCs
The unbuffered external reference mode allows for pre-
cise control over the MAX12559 reference and allows
multiple converters to use a common reference.
Connecting REFIN to GND disables the internal refer-
ence, allowing REF_P, REF_N, and COM_ to be driven
directly by a set of external reference sources.
Figure 13 uses a MAX6029 precision 3.000V bandgap
reference as a common reference for multiple convert-
ers. A seven-component resistive divider chain follows
the MAX6029 voltage reference. The 0.47µF capacitor
along this chain creates a 10Hz LP filter. Three
MAX4230 amplifiers buffer taps along this resistor
chain providing 2.413V, 1.647V, and 0.880V to the
MAX12559 REF_P, REF_N, and COM_ reference inputs.
The feedback around the MAX4230 op amps provides
additional 10Hz LP filtering. Reference voltages 2.413V
and 0.880V set the full-scale analog input range for the
converter to ±1.022V (±[V_{REF_P} - V_{REF_N}] x 2/3).
Note that one single power supply for all active circuit
components removes any concern regarding power-
supply sequencing when powering up or down.
Table 4. Component Selection to
Enhance the Frequency-Range-Specific
AC Performance
INPUT
FREQUENCY
RANGE
< 10MHz
10MHz to 125MHz
> 125MHz
C_IN
COMPONENT
VALUES
12pF to 22pF
12pF
5.6pF
R_IN
COMPONENT
VALUES
0Ω
50Ω
0Ω
V_IN
0.1μF _0Ω
MAX4108
100Ω
24.9Ω
5.6pF
100Ω
24.9Ω
0.1μF
5.6pF
IN_P
MAX12559
COM_
IN_N
Figure 11. Single-Ended, AC-Coupled Input Drive
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