LMP90077MHENOPB National Semiconductor, LMP90077MHENOPB Datasheet - Page 29

• Manufacturer Part Number: LMP90077MHENOPB
• Description: IC AFE 16BIT 214.6SPS 28-TSSOP
• Manufacturer: National Semiconductor
• Series: -r

Specifications of LMP90077MHENOPB

• Number Of Bits: 16
• Number Of Channels: 2 Differential, 4 Single-Ended
• Power (watts): -
• Voltage - Supply, Analog: 2.85 V ~ 5.5 V
• Voltage - Supply, Digital: 2.7 V ~ 5.5 V
• Package / Case: 28-TSSOP (0.173", 4.40mm Width)
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: LMP90077MHENOPBTR

4.
5.
System Calibration Gain Coefficient Determination mode
1.
2.
3.
4.
5.
6.
7.
Post-calibration Scaling
LMP900xx allows scaling (multiplication and shifting) for the
System Calibrated result. This eases downstream process-
ing, if any. Multiplication is done using the System Calibration
Scaling Coefficient in the CHx_SCAL_SCALING register and
shifting is done using the System Calibration Bits Selector in
the CHx_SCAL_BITS_SELECTOR register.
The System Calibration Bits Selector value should ideally be
the logarithm (to the base 2) of the System Calibration Scaling
Coefficient value.
There are four distinct sets of System Calibration Scaling and
System Calibration Bits Selector Registers for use with CH0-
CH3. CH4-CH6 reuse the registers of CH0-CH2, respectively.
A data-flow diagram of these coefficients can be seen in
ure 15
the conversion, the CHx_SCAL_OFFSET register is
filled-in with the System Calibration Offset coefficient.
The System Calibration Offset Coefficient Determination
mode is automatically exited.
The computed calibration coefficient is accurate only to
the effective resolution of the device and will probably
contain some noise. The noise factor can be minimized
by computing over many times, averaging (externally)
and putting the resultant value back into the register.
Alternatively, select the output data rate to be 26.83 sps
or 1.67 sps.
Repeat the System Calibration Offset Coefficient
Determination to calibrate the System offset for the
channel.
Apply the system reference-scale condition to the
channel CH0/CH1/CH2/CH3.
In the CHx_SCAL_GAIN register, program the expected
(desired) system-calibrated output code for this condition
in 16-bit unsigned format.
Enter the System Calibration Gain Coefficient
Determination mode by programming 0x3 in the
SCALCN register.
LMP900xx starts a fresh conversion at the selected
output data rate for the channel. At the end of the
conversion, the CHx_SCAL_GAIN is filled-in (or
overwritten) with the System Calibration Gain coefficient.
The System Calibration Gain Coefficient Determination
mode is automatically exited.
The computed calibration coefficient is accurate only to
the effective resolution of the device and will probably
contain some noise. The noise factor can be minimized
by computing over many times, averaging (externally)
and putting the resultant value back into the register.
Alternatively, select the output data rate to be 26.83 sps
or 1.67 sps.
Fig-
29
16.3 CHANNELS SCAN MODE
There are four scan modes. These scan modes are selected
using the CH_SCAN: CH_SCAN_SEL bit. The first scanned
channel is FIRST_CH, and the last scanned channel is
LAST_CH; they are both located in the CH_SCAN register.
The CH_SCAN register is double buffered. That is, user in-
puts are stored in a slave buffer until the start of the next
conversion during which time they are transferred to the mas-
ter buffer. Once the slave buffer is written, subsequent up-
dates are disregarded until a transfer to the master buffer
happens. Hence, it may be appropriate to check the
CH_SCAN_NRDY bit before programming the CH_SCAN
register.
ScanMode0: Single-Channel Continuous Conversion
LMP900xx continuously converts the selected FIRST_CH.
Do not operate in this scan mode if gain
P900xx is running in background calibration modes Bg-
calMode1 or BgcalMode2. If this is the case, then it is more
suitable to operate the device in ScanMode2 instead.
ScanMode1: Multiple-Channels Single Scan
LMP900xx converts one or more channels starting from
FIRST_CH to LAST_CH, and then enters the stand-by state.
ScanMode2: Multiple-Channels Continuous Scan
LMP900xx continuously converts one or more channels start-
ing from FIRST_CH to LAST_CH, and then it repeats this
process.
ScanMode3: Multiple-Channels Continuous Scan with
Burnout Currents
This mode is the same as ScanMode2 except that the burnout
current is provided in a serially scanned fashion (injected in a
channel after it has undergone a conversion). Thus it avoids
burnout current injection from interfering with the conversion
result for the channel.
The sensor diagnostic burnout currents are available for all
four scan modes. The burnout current is further gated by the
BURNOUT_EN bit for each channel. ScanMode3 is the only
mode that scans multiple channels while injecting burnout
currents without interfering with the signal. This is described
in details in
FIGURE 15. Post-calibration Scaling Data-Flow Diagram
Section 16.4.2 Burnout
Currents.
≥
16 and the LM-
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