Datasheet

• External-Acquisition-Mode Control Byte
• Internal-Clock-Mode Control Byte
• Reset Byte
• Partial Power-Down-Mode Control Byte
This prevents the MAX1300/MAX1301 from inadvertently
exiting full power-down mode because of a CS glitch in a
noisy digital environment.
Power-On Reset
The MAX1300/MAX1301 power up in normal operation
configured for external clock mode with all circuitry active
(Tables 7 and 8). Each analog input channel (CH0–CH7) is
set for single-ended conversions with a ±3 x V
REF
bipolar
input range (Table 6).
Allow the power supplies to stabilize after power-up. Do not
initiate any conversions until the power supplies have sta-
bilized. Additionally, allow 10ms for the internal reference to
stabilize when C
REF
= 1.0μF and C
REFCAP
= 0.1μF. Larger
reference capacitors require longer stabilization times.
Internal or External Reference
The MAX1300/MAX1301 operate with either an internal
or external reference. The reference voltage impacts the
ADC’s FSR (Figures 12, 13, and 14). An external refer-
ence is recommended if more accuracy is required than
the internal reference provides, and/or multiple converters
require the same reference voltage.
Internal Reference
The MAX1300/MAX1301 contain an internal 4.096V
bandgap reference. This bandgap reference is connected
to REFCAP through a nominal 5kΩ resistor (Figure 17).
The voltage at REFCAP is buffered creating 4.096V at
REF. When using the internal reference, bypass REFCAP
with a 0.1μF or greater capacitor to AGND1 and bypass
REF with a 1.0μF or greater capacitor to AGND1.
External Reference
For external reference operation, disable the internal
reference and reference buffer by connecting REFCAP
to AVDD1. With AVDD1 connected to REFCAP, REF
becomes a high-impedance input and accepts an external
reference voltage. The MAX1300/MAX1301 can accept
an external reference voltage of 4.096V or less. However,
to meet all of the electrical characteristic specifications,
V
REF
must be > 38V. The MAX1300/ MAX1301 external
reference current varies depending on the applied refer-
ence voltage and the operating mode (see the External
Reference Input Current vs. External Reference Input
Voltage in the Typical Operating Characteristics).
Applications Information
Noise Reduction
Additional samples can be taken and averaged (oversam-
pling) to remove the effect of transition noise on conver-
sion results. The square root of the number of samples
determines the improvement in performance. For example,
with 2/3LSB
RMS
(4LSB
P-P
) transition noise, 16 (4
2
= 16)
samples must be taken to reduce the noise to 1LSB
P-P
.
Interface with 0 to 10V Signals
In industrial control applications, 0 to 10V signaling is
common. For 0 to 10V applications, configure the selected
MAX1300/MAX1301 input channel for the single-ended 0
to 3 x V
REF
input range (R[2:0] = 110, Table 6). The 0 to 3
x V
REF
range accommodates 0 to 10V where the signals
saturate at approximately 3 x V
REF
if out of range.
Interface with 4–20mA Signals
Figure 19 illustrates a simple interface between the
MAX1300/MAX1301 and a 4–20mA signal. 4–20mA sig-
naling can be used as a binary switch (4mA represents
a logic-low signal, 20mA represents a logic-high signal),
or for precision communication where currents between
4mA and 20mA represent intermediate analog data. For
binary switch applications, connect the 4–20mA signal
to the MAX1300/MAX1301 with a resistor to ground. For
example, a 250Ω resistor converts the 4–20mA signal to
a 1V to 5V signal. Adjust the resistor value so the parallel
combination of the resistor and the MAX1300/MAX1301
source impedance is 250Ω. In this application, select the
single-ended 0 to (3 x V
REF
)/2 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 MAX1300/MAX1301 input from
diverting current from the 4–20mA signal.
Figure 17. Internal Reference Operation
REF
REFCAP
AGND1
4.096V
BANDGAP
REFERENCE
5kΩ
1x
SAR
ADC
REF
4.096V
1.0µF
0.1µF
V
RCTH
MAX1300
MAX1301
MAX1300/MAX1301 8- and 4-Channel, ±3 x V
REF
Multirange Inputs,
Serial 16-Bit ADCs
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