Datasheet

MAX1192
Ultra-Low-Power, 22Msps, Dual 8-Bit ADC
______________________________________________________________________________________ 23
Figure
11 shows the MAX6066 precision bandgap ref-
erence used as a common reference for multiple con-
verters. The 2.500V output of the MAX6066 is followed
by a 10Hz lowpass filter and precision voltage-divider.
The MAX4254 buffers the taps of this divider to provide
the 1.75V, 1.5V, and 1.25V sources to drive REFP,
REFN, and COM. The MAX4254 provides a low offset
voltage and low noise level. The individual voltage fol-
lowers are connected to 10Hz lowpass filters, which fil-
ter both the reference-voltage and amplifier noise to a
level of 3nV/√Hz. The 1.75V and 1.25V reference volt-
ages set the differential full-scale range of the associat-
ed ADCs at ±0.5V.
The common power supply for all active components
removes any concern regarding power-supply
sequencing when powering up or down.
With the outputs of the MAX4252 matching better than
0.1%, the buffers and subsequent lowpass filters sup-
port as many as 160 MAX1192s.
MAX4254
1/4
47Ω
3V
2
2
2.500V
3
1
1
REFP
V
DD
MAX1192
N = 1
27
GND
NOTE: ONE FRONT-END
REFERENCE CIRCUIT
SUPPORTS UP TO 160 MAX1192s
3
0.1μF
10μF
6V
1μF
1%
30.1kΩ
1%
10.0kΩ
0.1μF
2.2μF
330μF
6V
0.33μF
26
24
0.33μF
REFN
REFIN
REFIN
25
0.33μF
COM
MAX6066
1.748V
1%
10.0kΩ
1%
49.9kΩ
REFP
V
DD
MAX1192
N = 160
27
GND
0.33μF
26
24
0.33μF
REFN
25
0.33μF
COM
1.47kΩ
MAX4254
47Ω
6
5
7
10μF
6V
330μF
6V
1.498V
1.47kΩ
47Ω
9
10
8
10μF
6V
330μF
6V
1.248V
MAX4254
1.47kΩ
1MΩ
MAX4254
13
12
14
11
4
0.1μF
UNCOMMITTED
1MΩ
3V
1/4
1/4
1/4
Figure 11. External Unbuffered Reference Driving 160 ADCs with MAX4254 and MAX6066