Datasheet

ground should be low impedance and as short as pos-
sible for noise-free operation.
High-frequency noise in the V
DD
power supply may
affect the high-speed comparator in the ADC. Bypass
the supply to the star ground with 0.1µF and 4.7µF
capacitors close to pin 20 of the MAX1245. Minimize
capacitor lead lengths for best supply-noise rejection. If
the +2.5V power supply is very noisy, a 10Ω resistor
can be connected as a lowpass filter (Figure 16).
MAX1245
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
______________________________________________________________________________________ 17
OUTPUT CODE
FULL-SCALE
TRANSITION
11 . . . 111
11 . . . 110
11 . . . 101
00 . . . 011
00 . . . 010
00 . . . 001
00 . . . 000
123
0
(COM)
FS
FS - 3/2LSB
FS = VREF + COM
ZS = COM
INPUT VOLTAGE (LSBs)
1LSB =
VREF
4096
011 . . . 111
011 . . . 110
000 . . . 010
000 . . . 001
000 . . . 000
111 . . . 111
111 . . . 110
111 . . . 101
100 . . . 001
100 . . . 000
- FS
COM
INPUT VOLTAGE (LSBs)
OUTPUT CODE
ZS = COM
+FS - 1LSB
( VREF/2)
+ COM
FS
=
VREF
2
-FS = + COM
-VREF
2
1LSB =
VREF
4096
≤
Figure 14. Unipolar Transfer Function, Full Scale (FS) = VREF
+ COM, Zero Scale (ZS) = COM
Figure 15. Bipolar Transfer Function, Full Scale (FS) = VREF /
2 + COM, Zero Scale (ZS) = COM
+2.5V
+2.5V
GND
SUPPLIES
DGND+2.5VDGNDCOM
AGNDV
DD
DIGITAL
CIRCUITRY
MAX1245
R* = 10Ω
* OPTIONAL
Figure 16. Power-Supply Grounding Connection