MAX1196 Datasheet, PDF (19/23 Pages) Maxim Integrated Products – Dual 8-Bit, 40Msps, 3V, Low-Power ADC with Internal Reference and Multiplexed Parallel Outputs

Dual 8-Bit, 40Msps, 3V, Low-Power ADC with
Internal Reference and Multiplexed Parallel Outputs
3.3V
0.1µF
1
MAX6066
2 ^21.5kΩ
3
1µF
3.3V
0.1µF
MAX4254 POWER-SUPPLY
BYPASSING. PLACE CAPACITOR
AS CLOSE AS POSSIBLE TO
THE OP AMP.
2.0V
3
2
21.5kΩ
1.5V
5
6
21.5kΩ
1.0V
10
21.5kΩ
9
21.5kΩ
3.3V
4
1/4 MAX4252
1
2.0V AT 8mA
47kΩ
11
10µF
330µF
6V
6V
1.47kΩ
3.3V
4
1/4 MAX4252
7
1.5V AT 0mA
47kΩ
11
10µF
6V
330µF
6V
1.47kΩ
3.3V
4
1/4 MAX4252
8
1.0V AT -8mA
47kΩ
11
10µF
6V
330µF
6V
1.47kΩ
NOTE: ONE FRONT-END REFERENCE CIRCUIT DESIGN CAN BE USED WITH UP TO 32 ADCs.
N.C.
29 _REFOUT
31 _REFIN
32 _REFP
1 _{REFN N = 1}
MAX1196
2 _COM
0.1µF 0.1µF 0.1µF
0.1µF
N.C.
29 _REFOUT
31
REFIN
32
REFP
N = 32
1 _{REFN MAX1196}
2 _COM
0.1µF 0.1µF 0.1µF
2.2µF
10V
Figure 9. External Unbuffered Reference Drive With MAX4252 and MAX6066
Typical QAM Demodulation Application
A frequently used modulation technique in digital com-
munications applications is quadrature amplitude mod-
ulation (QAM). Typically found in spread- spectrum-
based systems, a QAM signal represents a carrier fre-
quency modulated in both amplitude and phase. At the
transmitter, modulating the baseband signal with quad-
rature outputs, a local oscillator followed by subse-
quent up-conversion can generate the QAM signal. The
result is an in-phase (I) and a quadrature (Q) carrier
component, where the Q component is 90 degrees
phase-shifted with respect to the in-phase component.
At the receiver, the QAM signal is divided down into its
I and Q components, essentially representing the mod-
ulation process reversed. Figure 10 displays the
demodulation process performed in the analog domain,
using the dual matched 3V, 8-bit ADC MAX1196, and
the MAX2451 quadrature demodulator to recover and
digitize the I and Q baseband signals. Before being
digitized by the MAX1196, the mixed-down signal com-
ponents can be filtered by matched analog filters, such
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