Datasheet

MAX1303
4-Channel, ±V
REF
Multirange Inputs,
Serial 16-Bit ADC
______________________________________________________________________________________ 25
REF
REFCAP
AGND1
4.096V
BANDGAP
REFERENCE
5kΩ
1x
SAR
ADC
REF
4.096V
1.0µF
V
RCTH
MAX1303
AVDD1
MAX6341
V+
1.0µF
OUT
GND
IN
Figure 17. External Reference Operation
Applications Information
Noise Reduction
Additional samples can be taken and averaged (over-
sampling) to remove the effect of transition noise on
conversion results. The square root of the number of
samples determines the improvement in performance.
For example, with 2/3 LSB
RMS
(4 LSB
P-P
) transition
noise, 16 (4
2
= 16) samples must be taken to reduce
the noise to 1 LSB
P-P
.
Interface with 4–20mA Signals
Figure 18 illustrates a simple interface between the
MAX1303 and a 4–20mA signal. 4–20mA signaling can
be used as a binary switch (4mA represents a logic-low
signal, 20mA represents a logic-high signal), or for pre-
cision communication where currents between 4mA
and 20mA represent intermediate analog data. For
binary switch applications, connect the 4–20mA signal
to the MAX1303 with a resistor to ground. For example,
a 200Ω resistor converts the 4–20mA signal to a 0.8V to
4V signal. Adjust the resistor value so the parallel com-
bination of the resistor and the MAX1303 source
impedance is 200Ω. In this application, select the sin-
gle-ended 0V to V
REF
range (R[2:0] = 011, Table 6).
For applications that require precision measurements
of continuous analog currents between 4mA and 20mA,
use a buffer to prevent the MAX1303 input from divert-
ing current from the 4–20mA signal.
MAX1303
CH0
REF
µP
CH1
LOW-OFFSET
DIFFERENTIAL
AMPLIFIER
BRIDGE
Figure 18. Bridge Application