MAX11253 Datasheet, PDF (35/51 Pages) Maxim Integrated Products – Longer Battery Life for Portable Applications

MAX11253
16-Bit, 6-Channel, 64ksps, 6.2nV/√Hz PGA,
Delta-Sigma ADC with SPI Interface
SINC5 FILTER, NORMAL MODE
REJECTION DATA RATE 64000.0sps
0
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FREQUENCY (Hz)
x 10⁴
Figure 19. Digital Filter Frequency Response for 64ksps
Continuous Data Rate and 12.8ksps Single-Cycle Data Rate
MODULATOR ANALOG OVERRANGE
The modulator analog overrange is used to signal the user
that the input analog voltage has exceeded preset limits
defined by the modulator operating range. These limits
are approximately 120% of the applied reference voltage.
When analog overrange is detected the STAT:AOR bit is
set to ‘1’ after DATA is updated. The AOR bit will always
correspond to the current value in the DATA register. See
Table 7.
SINC Filter
The digital filter is a mode-configurable digital filter and
decimator that processes the data stream from the fourth
order delta-sigma modulator and implements a fifth order
SINC function with an averaging function to produce a
24-bit wide data stream.
The SINC filter allows the MAX11253 to achieve very
high SNR. The bandwidth of the fifth order SINC filter
is approximately twenty percent of the data rate. See
Figures 19 and 20 for the filter response of 64ksps and
4ksps, respectively. See Figure 21 for the bandwidth of
the individual signal stages.
Applications Information
Connecting an External 1.8V Supply to DVDD
for Digital I/O and Digital Core
The voltage range of the DVDD I/O supply is specified
from 2.0V to 3.6V if the internal LDO is used to power the
digital core. If a lower I/O supply voltage is desired, the
SINC5 FILTER, NORMAL MODE REJECTION
SINGLE CYCLE DATA RATE 4000.0sps
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0123456
FREQUENCY (Hz)
x 10⁴
Figure 20. Digital Filter Frequency Response for 4ksps Single-
Cycle Data Rate
internal LDO can be disabled, and DVDD and CAPREG
can be connected together as shown in Figure 22. In this
mode of operation, DVDD can vary from 1.7V to 2.0V. The
internal LDO must be disabled by setting CTRL2:LDOEN to ‘0’.
Split Supplies
The MAX11253 supports unipolar and split analog power
supplies for input range flexibility. Using a split analog
supply enables sampling below ground reference. The
true bipolar input range is up to ±1.8V. See Figure 3 for
analog input voltage range for both unipolar and split
supplies.
Sensor Fault Detection
The MAX11253 includes a 1µA current source and a
1µA current sink. The source pulls current from AVDD to
AIN_P and sink from AIN_N to AVSS. The currents are
enabled by register bit CTRL3:CSSEN. These currents
are used to detect damaged sensors in either open or
shorted state. The current sources and sinks are func-
tional over the normal input operating voltage range, as
specified.
These currents are used to test sensors for functional
operation before taking measurements on that input
channel. With the source and sink enabled, the currents
flow into the external sensor circuit and measurement
of the input voltage is used to diagnose sensor faults. A
full-scale reading could indicate a sensor is open circuit
or overloaded or that the ADC’s reference is absent. If a
zero-scale is read back, this may indicate the sensor is
short-circuited.
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