MAX1191 Datasheet, PDF (21/27 Pages) Maxim Integrated Products – Ultra-Low-Power, 7.5Msps, Dual 8-Bit ADC

Ultra-Low-Power, 7.5Msps, Dual 8-Bit ADC
3V
0.1µF
1.248V
1
2
MAX6061
3
10Hz
LOWPASS
FILTER
1%
20kΩ
1µF
1%
90.9kΩ
3V
NOTE: ONE FRONT-END REFERENCE
3
5
CIRCUIT PROVIDES ±15mA OF OUTPUT
DRIVE AND SUPPORTS OVER 1000 MAX1191s.
4
MAX4250
2
0.1µF
1 ^15Ω
24 _REFIN ^VDD
0.1µF
0.33µF
0.33µF
27 _{REFP N = 1}
MAX1191
26 _REFN
25 _COM
0.33µF
GND
1.023V
24 _REFIN ^VDD
0.1µF
0.33µF
0.33µF
27 _{REFP N = 1000}
MAX1191
26 _REFN
25 _COM
0.33µF
GND
0.1µF
2.2µF
Figure 10. External Buffered (MAX4250) Reference Drive Using a MAX6062 Bandgap Reference
Figure 10 shows the MAX6061 precision bandgap ref-
erence used as a common reference for multiple con-
verters. The 1.248V output of the MAX6061 is divided
down to 1.023V as it passes through a one-pole, 10Hz,
lowpass filter to the MAX4250. The MAX4250 buffers
the 1.023V reference before its output is applied to the
MAX1191. The MAX4250 provides a low offset voltage
(for high gain accuracy) and a low noise level.
Unbuffered External Reference Drives
Multiple ADCs
The unbuffered external reference mode allows for pre-
cise control over the MAX1191 reference and allows
multiple converters to use a common reference.
Connecting REFIN to GND disables the internal refer-
ence, allowing REFP, REFN, and COM to be driven
directly by a set of external reference sources.
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