MAX1245 Maxim, MAX1245 Datasheet - Page 17

• Manufacturer Part Number: MAX1245
• Description: +2.375V / Low-Power / 8-Channel / Serial 12-Bit ADC
• Manufacturer: Maxim

ground should be low impedance and as short as pos-
sible for noise-free operation.
High-frequency noise in the V
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).
Figure 14. Unipolar Transfer Function, Full Scale (FS) = VREF
+ COM, Zero Scale (ZS) = COM
11 . . . 111
11 . . . 110
00 . . . 011
00 . . . 010
11 . . . 101
00 . . . 001
00 . . . 000
OUTPUT CODE
(COM)
0
1
2
______________________________________________________________________________________
3
INPUT VOLTAGE (LSBs)
TRANSITION
FULL-SCALE
DD
power supply may
FS - 3/2LSB
+2.375V, Low-Power, 8-Channel,
FS = VREF + COM
ZS = COM
1LSB =
FS
VREF
4096
Figure 15. Bipolar Transfer Function, Full Scale (FS) = VREF /
2 + COM, Zero Scale (ZS) = COM
Figure 16. Power-Supply Grounding Connection
R* = 10
011 . . . 111
011 . . . 110
000 . . . 010
000 . . . 001
000 . . . 000
111 . . . 111
111 . . . 110
111 . . . 101
100 . . . 001
100 . . . 000
* OPTIONAL
OUTPUT CODE
+2.5V
V
DD
Serial 12-Bit ADC
- FS
AGND
-FS =
MAX1245
1LSB =
FS =
ZS = COM
-VREF
VREF
2
2
VREF
4096
INPUT VOLTAGE (LSBs)
+ COM
SUPPLIES
+ COM
COM
( VREF/2)
COM
DGND
+2.5V
+2.5V
CIRCUITRY
DIGITAL
+FS - 1LSB
DGND
GND
17