MAX1448 Datasheet, PDF (16/21 Pages) Maxim Integrated Products – 10-Bit, 80Msps, Single 3.0V, Low-Power ADC with Internal Reference

10-Bit, 80Msps, Single 3.0V, Low-Power
ADC with Internal Reference
3.3V
0.1µF
3.3V
0.1µF
2.048V
1
MAX6062
3
16.2kΩ
2
1µF
10Hz LOWPASS
FILTER
0.1µF
3
5
MAX4250
4
2
162Ω
1
100µF
10Hz LOWPASS
FILTER
0.1µF
N.C. 29 _REFOUT
31 _REFIN
32 _{REFP MAX1448}
1 _REFN ^{N = 1}
2 _COM
0.1µF 0.1µF
0.1µF
0.1µF
0.1µF
N.C. 29 _REFOUT
31 _REFIN
32 _{REFP MAX1448}
1
N = 1000
REFN
2 _COM
0.1µF 0.1µF
2.2µF
10V
NOTE: ONE FRONT-END REFERENCE CIRCUIT DESIGN MAY BE USED WITH UP TO 1000 ADCs.
Figure 10. Buffered External Reference Drives Up to 1000 ADCs
Buffered External Reference
Drives Multiple ADCs
Multiple-converter systems based on the MAX1448 are
well suited for use with a common reference voltage.
The REFIN pin of those converters can be connected
directly to an external reference source. A precision
bandgap reference like the MAX6062 generates an
external DC level of 2.048V (Figure 10), and exhibits a
noise voltage density of 150nV/√Hz. Its output passes
through a 1-pole lowpass filter (with 10Hz cutoff fre-
quency) to the MAX4250, which buffers the reference
before its output is applied to a second 10Hz lowpass
filter. The MAX4250 provides a low offset voltage (for
high-gain accuracy) and a low noise level. The passive
10Hz filter following the buffer attenuates noise pro-
duced in the voltage reference and buffer stages. This
filtered noise density, which decreases for higher fre-
quencies, meets the noise levels specified for precision
ADC operation.
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