Rainbow Electronics MAX1449 - Manual (Page 14)

MAX1449
10-Bit, 105Msps, Single +3.3V, Low-Power
ADC with Internal Reference
14 ______________________________________________________________________________________
the use of a split ground plane arranged to match the
physical location of the analog ground (GND) and the
digital output driver ground (OGND) on the ADC's
package. The two ground planes should be joined at a
single point, such that the noisy digital ground currents
do not interfere with the analog ground plane. The ideal
location of this connection can be determined experi-
mentally at a point along the gap between the two
ground planes, which produces optimum results. Make
this connection with a low-value, surface-mount resistor
(1
Ω to 5Ω), a ferrite bead or a direct short. Alternatively,
all ground pins could share the same ground plane, if
the ground plane is sufficiently isolated from any noisy
digital systems ground plane (e.g., downstream output
buffer or DSP ground plane). Route high-speed digital
signal traces away from sensitive analog traces. Keep
all signal lines short and free of 90° turns.
Static Parameter Definitions
Integral Nonlinearity (INL)
Integral nonlinearity is the deviation of the values on an
actual transfer function from a straight line. This straight
line can be either a best straight-line fit or a line drawn
between the endpoints of the transfer function, once
offset and gain errors have been nullified. The static lin-
earity parameters for the MAX1449 are measured using
the best straight-line fit method.
INPUT
300 Ω
-5V
+5V
0.1 µF
0.1 µF
0.1 µF
C
IN
22pF
C IN
22pF
R ISO
50 Ω
R ISO
50 Ω
-5V
600 Ω
300 Ω
300 Ω
IN+
IN-
LOWPASS FILTER
COM
600 Ω
+5V
-5V
0.1 µF
600 Ω
300 Ω
600 Ω
300 Ω
0.1 µF
0.1 µF
0.1 µF
+5V
0.1 µF
300 Ω
MAX4108
MAX1449
MAX4108
MAX4108
LOWPASS FILTER
Figure 7. Typical Application Circuit Using the Internal Reference