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 0.1µF and

4.7µF

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

Ω 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

0.01µF

12

REFADJ

MAX1202

Figure 17. MAX1202 Reference-Adjust Circuit