Datasheet

MAX1191
Ultra-Low-Power, 7.5Msps, Dual 8-Bit ADC
______________________________________________________________________________________ 21
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.
MAX4250
3V
2
4
2
1.248V
3
5
10Hz
LOWPASS
FILTER
1
15Ω
1
REFIN
V
DD
MAX1191
N = 1
24
GND
1.023V
NOTE: ONE FRONT-END REFERENCE
CIRCUIT PROVIDES ±15mA OF OUTPUT
DRIVE AND SUPPORTS OVER 1000 MAX1191s.
3
0.1µF
0.1µF
3V
1µF
1%
20kΩ
1%
90.9kΩ
0.1µF
2.2µF
0.1µF
REFP
27
0.33µF
REFN
26
0.33µF
COM
25
0.33µF
REFIN
V
DD
MAX1191
N = 1000
24
GND
0.1µF
REFP
27
0.33µF
REFN
26
0.33µF
COM
25
0.33µF
MAX6061
Figure 10. External Buffered (MAX4250) Reference Drive Using a MAX6062 Bandgap Reference