Datasheet
Bridge Application
The MAX1300/MAX1301 convert 1kHz signals more
accurately than a similar sigma-delta converter that might
be considered in bridge applications. The input impedance
of the MAX1300, in combination with the current-limiting
resistors, can affect the gain of the MAX1300. In many
applications this error is acceptable, but for applications
that cannot tolerate this error, the MAX1300 inputs can be
buffered (Figure 20). Connect the bridge to a low-offset
differential amplifier and then the true-differential inputs of
the MAX1300/MAX1301. Larger excitation voltages take
advantage of more of the (±3 x V
REF
)/4 differential input
voltage range. Select an input voltage range that matches
the amplifier output. Be aware of the amplifier offset and
offset-drift errors when selecting an appropriate amplifier.
Dynamically Adjusting the Input Range
Software control of each channel’s analog input range
and the unipolar endpoint overlap specification make it
possible for the user to change the input range for a chan-
nel dynamically and improve performance in some appli-
cations. Changing the input range results in a small LSB
step-size over a wider output voltage range. For example,
by switching between a (-3 x V
REF
)/2 to 0V range and a 0
to (+3 x V
REF
)/2 range, an LSB is
REF REF
( 3 V )/2 V
65,536 4.096
+× ×
×
but the input voltage range effectively spans from (-3 x
V
REF
)/2 to (+3 x V
REF
)/2 (FSR = 3 x V
REF
).
Layout, Grounding, and Bypassing
Careful PC board layout is essential for best system
performance. Boards should have separate analog and
digital ground planes and ensure that digital and analog
signals are separated from each other. Do not run analog
and digital (especially clock) lines parallel to one another,
or digital lines underneath the device package.
Figure 1 shows the recommended system ground con-
nections. Establish an analog ground point at AGND1
and a digital ground point at DGND. Connect all analog
grounds to the star analog ground. Connect the digital
grounds to the star digital ground. Connect the digital
ground plane to the analog ground plane at one point.
For lowest noise operation, make the ground return to the
star ground’s power-supply low impedance and as short
as possible.
High-frequency noise in the AVDD1 power supply
degrades the ADC’s high-speed comparator performance.
Bypass AVDD1 to AGND1 with a 0.1μF ceramic surface-
mount capacitor. Make bypass capacitor connections as
short as possible.
Parameter Denitions
Integral Nonlinearity (INL)
INL is the deviation of the values on an actual transfer
function from a straight line. This straight line is 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 MAX1300/MAX1301 INL is measured
using the endpoint method.
Figure 18. External Reference Operation
REF
REFCAP
AGND1
4.096V
BANDGAP
REFERENCE
5kΩ
1x
SAR
ADC
REF
4.096V
1.0µF
V
RCTH
MAX1300
MAX1301
AV
DD1
MAX6341
V+
1.0µF
OUT
GND
IN
MAX1300/MAX1301 8- and 4-Channel, ±3 x V
REF
Multirange Inputs,
Serial 16-Bit ADCs
www.maximintegrated.com
Maxim Integrated
│
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