
MAX1202/MAX1203
5V, 8-Channel, Serial, 12-Bit ADCs
with 3V Digital Interface
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21
Figure 16. Bipolar Transfer Function, ±4.096V/2 = Full Scale
Figure 15. Unipolar Transfer Function, 4.096V = Full Scale
(“star” ground point) at GND. Connect all other analog
grounds to this ground. No other digital system ground
should be connected to this single-point analog
ground. The ground return to the power supply for this
ground should be low impedance and as short as pos-
sible for noise-free operation.
High-frequency noise in the power supplies can affect
the ADC’s high-speed comparator. Bypass these sup-
plies to the single-point analog ground with 0.1F and
4.7F
bypass
capacitors
close
to
the
MAX1202/MAX1203. Minimize capacitor lead lengths
for best supply-noise rejection. If the +5V power supply
is very noisy, a 10
resistor can be connected as a
lowpass filter, as shown in Figure 18.
OUTPUT CODE
FULL-SCALE
TRANSITION
11 . . . 111
11 . . . 110
11 . . . 101
00 . . . 011
00 . . . 010
00 . . . 001
00 . . . 000
12
3
0
FS
FS - 3/2LSB
+4.096V
+ 4.096V
4096
FS =
1LSB =
INPUT VOLTAGE (LSBs)
011 . . . 111
OUTPUT CODE
011 . . . 110
000 . . . 010
000 . . . 001
000 . . . 000
111 . . . 111
111 . . . 110
111 . . . 101
100 . . . 001
100 . . . 000
-FS
0V
INPUT VOLTAGE (LSBs)
+FS - 1LSB
FS = +2.048V
1LSB =
+4.096V
4096
+5V
510k
100k
24k
0.01F
12
REFADJ
MAX1202
Figure 17. MAX1202 Reference-Adjust Circuit