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MAX11209 View Datasheet(PDF) - Maxim Integrated

Part NameDescriptionManufacturer
MAX11209 18-Bit, Single-Channel, Ultra-Low-Power, DeltaSigma ADCs with Programmable Gain and GPIO MaximIC
Maxim Integrated MaximIC
MAX11209 Datasheet PDF : 27 Pages
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MAX11209/MAX11211
18-Bit, Single-Channel, Ultra-Low-Power, Delta-
Sigma ADCs with Programmable Gain and GPIO
2.048MHz oscillator. The 2.4576MHz oscillator provides
maximum 60Hz rejection, and the 2.048MHz oscillator
provides maximum 50Hz rejection. See Figures 1 and
2. For optimal simultaneous 50Hz and 60Hz rejection,
apply a 2.25275MHz external clock at CLK.
Reference
The devices provide differential inputs REFP and REFN
for an external reference voltage. Connect the external
reference directly across the REFP and REFN to obtain
the differential reference voltage. The common-mode
voltage range for VREFP and VREFN is between 0 and
VAVDD.
The devices accept reference inputs in buffered or
unbuffered mode. The value of the REFBUF bit in the
CTRL1 register determines whether the reference buffer
is enabled or disabled. See Table 12.
Buffers
The devices include reference and signal input buffers
capable of reducing the average input current from
2.1FA/V on the reference inputs and from 1.4FA/V on
the analog inputs to a constant 30nA current on the
reference inputs and 20nA current on the analog inputs.
The reference and signal input buffers can be selected
individually by programming the CTRL1 register bits
REFBUF and SIGBUF. When enabled, the reference and
input signal buffers require an additional 20FA from the
AVDD supply pin.
Power-On Reset (POR)
The devices utilize power-on reset (POR) supply-mon-
itoring circuitry on both the digital supply (DVDD) and
the analog supply (AVDD). The POR circuitry ensures
proper device default conditions after either a digital or
analog power sequencing event. The digital POR trig-
ger threshold is approximately 1.2V and has 100mV of
hysteresis. The analog POR trigger threshold is approxi-
mately 1.25V and has 100mV of hysteresis. Both POR
circuits have lowpass filters that prevent high-frequency
supply glitches from triggering the POR.
Calibration
The devices provide two sets of calibration registers
which offer the user several options for calibrating
their system. The calibration register value defaults
are all zero, which require a user to either perform
a calibration or program the register through the SPI
interface to use them. The on-chip calibration reg-
isters are enabled or disabled by programming the
NOSYSG, NOSYSO, NOSCG, and NOSCO bits in the
CTRL3 register. The default values for these calibra-
tion control bits are 1, which disables the use of the
internal calibration registers.
The devices power up with the internal calibration regis-
ters disabled, and therefore a full-scale input produces
a result of 60% of the full-scale digital range. To use the
full-scale digital range a calibration must be performed.
The first level of calibration is the self-calibration where
the part performs the required connections to zero and
full-scale internally. This level of calibration is typically
sufficient for 1FV of offset accuracy and 2ppm of full-
scale accuracy. The self-calibration routine does not
include the source resistance effects from the signal
source driving the input pins, which can change the off-
set and gain of the system.
A second level of calibration is available where the user
can calibrate a system zero scale and system full scale
by presenting a zero-scale signal or a full-scale signal
to the input pins and initiating a system zero scale or
system gain calibration command.
A third level of calibration allows for the user to write to
the internal calibration registers through the SPI interface
to achieve any digital offset or scaling the user requires
with the following restrictions. The range of digital offset
correction is QVREF/4. The range of digital gain correc-
tion is from 0.5 to 1.5. The resolution of offset correction
is 0.5 LSB.
The calibration operations are controlled with the CAL1
and CAL0 bits in the command byte. The user requests
a self-calibration by setting the CAL1 bit to 0 and CAL0
bit to 1. A self-calibration requires 200ms to complete,
and both the SCOC and SCGC registers contain the
values that correct the chip output for zero scale and full
scale. The user requests a system zero-scale calibration
by setting the CAL1 bit to 1 and the CAL0 bit to 0 and
presents a system zero-level signal to the input pins. The
SOC register contains the values that correct the chip
zero scale. The system zero calibration requires 100ms
to complete, and the SOC register contains values that
correct the chip zero scale. The user requests a system
full-scale calibration by setting the CAL1 bit to 1 and the
CAL0 bit to 1 and presents a system full-scale signal
level to the input pins. The system full-scale calibration
requires 100ms to complete, and the SGC register con-
tains values that correct for the chip full-scale value. See
Tables 3a and 3b for an example of a self-calibration
sequence and a system calibration sequence.
10  
Maxim Integrated
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