MAX14001 Datasheet, PDF (12/34 Pages) Maxim Integrated Products – Configurable, Isolated 10-bit ADCs for Multi-Range Binary Inputs

MAX14001/MAX14002
Configurable, Isolated 10-bit ADCs for
Multi-Range Binary Inputs
Detailed Description
The MAX14001/MAX14002 are 10-bit ADCs with
a 3.75kV_RMS isolated SPI interface. Additional features
include a programmable magnitude comparator,
programmable inrush current for cleaning relay contacts,
and programmable input bias current to optimize power
dissipation while reducing capacitively coupled input
noise. The ADC and all field-side circuits are powered
by an integrated, isolated, DC-DC converter that allows
field-side functionality to be verified even when there is
no input signal or other field-side supply. This makes the
MAX14001/MAX14002 ideally suited for high density,
multi-range, individually isolated, binary input modules.
ADC
The devices’ ADC employs a 10-bit SAR architecture
with a nominal sampling rate of 10ksps, and has an input
voltage range of 0V to +1.25V with respect to AGND. After
power-up, the ADC runs continually at the nominal sampling
rate. The 10-bit unfiltered ADC reading and filtered ADC
reading are both available via the SPI interface. Filtering
averages the most recent 2, 4, or 8 readings depending
on the value of the FT[1:0] bits in the CFG register. A binary
comparator responds within 150µs to changes in input
voltage by continually comparing the latest ADC reading
to the programmed thresholds (refer to the EC table for
response times when using the ADC filter). When the latest
ADC reading is higher than the upper threshold (THU),
the comparator’s output pin (COUT) is high and when it
is lower than the lower threshold (THL), the comparator’s
output pin (COUT) is low.
Internal/External Voltage Reference Configuration
The MAX14001/MAX14002 feature both internal
and external voltage reference capability. The 1.25V
internal reference has a maximum error of ±5% over the
entire operating temperature range. If higher accuracy is
required, an external reference may be used. The external
reference may be either series or shunt, but must not
draw more than 70µA of supply current. Series references
must be powered from V_DDF while shunt references are
powered from an internal 70µA current source that is
connected to the REFIN pin. Internal/external voltage
reference mode is selected using the SPI interface to
program the CFG register. Refer to Table 1 for the
CFG register configuration, Figure 1 for shunt reference
hardware connection, and Figure 2 for series reference
hardware connection.
EXTERNAL V REF = 1.25V
NOMINAL
FIELD SIDE
REFIN
SHUNT
VOLTAGE
REFERENCE
0.1µF
AGND
AGND
MAX14001 /
MAX14002
0.1µF
VDDF
1000 pF ^GNDF
GNDF
REGISTER
CONFIGURATION :
CFG: EXRF = 1
CFG: EXTI = 1
Figure 1. Shunt Voltage Reference Connection
FIELD SIDE
SERIES VOLTAGE
REFERENCE
IN
EXTERNAL V REF = 1.25V
NOMINAL
OUT
REFIN
GND
AGND
0.1µF
AGND
MAX14001/
MAX14002
0.1µF
VDDF
1000pF ^GNDF
GNDF
REGISTER
CONFIGURATION :
CFG: EXRF = 1
CFG: EXTI = 0
Figure 2. Series Voltage Reference Connection
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