ADIS16250 Analog Devices, ADIS16250 Datasheet - Page 15

• Manufacturer Part Number: ADIS16250
• Description: Programmable Low Power Gyroscope
• Manufacturer: Analog Devices

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CALIBRATION
The ADIS16250 is factory-calibrated for sensitivity and bias.
It also provides several user calibration functions for
simplifying field-level corrections. The calibration factors are
stored in nonvolatile memory and are applied using the
following linear calibration equation:
There are three options for system-level calibrations of the bias
in the ADIS16250: auto null, factory calibration restore, and
manual calibration updates. The auto null and factory reset
options are described in the Global Commands section.
Optional field-level calibrations use the above equation and
require two steps: (1) characterize the behavior of the
ADIS16250 at predefined critical operating conditions, and (2)
use this characterization data to calculate and load the
appropriate adjustment factors into the GYRO_OFF (“b”).
The GYRO_SCALE (“m”) register can also be adjusted to
implement corrections in the sensitivity scale factor through the
system calibration process.
The GYRO_OFF provides a calibration range of ±37.5°/sec, and
its contents are nonvolatile. The GYRO_SCALE register
provides a calibration range of 0 to 1.9995, and its contents are
also nonvolatile.
Table 9. GYRO_OFF Register Definition
Address
0x11,
0x10
1
Table 10. GYRO_OFF Bit Descriptions
Bit
15:12
11:0
Table 11. GYRO_SCALE Register Definition
Address
0x13, 0x12
1 Scale is the weight of each LSB.
2 Equates to a scale factor of one.
Table 12. GYRO_SCALE Bit Descriptions
Bit
15:12
11:0
Scale is the weight of each LSB.
y = mx + b
where:
y = calibrated output data
x = precalibration data
m = sensitivity scale factor
b = offset scale factor
Description
Not used
Data bits
Description
Not used
Data bits
Scale
0.018315°/sec
Scale
0.0488%
1
1
Default
0x0000
Default
0x0800
2
Format
Twos
complement
Format
Binary
Access
R/W
Access
R/W
Rev. 0 | Page 15 of 20
GLOBAL COMMANDS
The ADIS16250 provides global commands for common
operations such as auto null, factory calibration restore, manual
FLASH update, auxiliary DAC latch, and software reset. Each of
these global commands has a unique control bit assigned to it in
the COMMAND register and is initiated by writing a 1 to its
assigned bit.
The auto null function does two things: it resets the contents of
the ANGL_OUT register to zero, and it adjusts the GYRO_OUT
register to zero. This automated adjustment takes two steps: (1)
read GYRO_OUT and (2) write the opposite of this value into
the GRYO_OFF register. Sensor noise influences the accuracy
of this step. For optimal calibration accuracy, set the number of
filtering taps to its maximum, wait for the appropriate number
of samples to process through the filter, and then exercise this
option.
The factory calibration restore command sets the contents of
GYRO_OFF to 0x0000 and GYRO_SCALE to 0x0800, erasing
any field-level calibration contents. The manual FLASH update
writes the contents of each nonvolatile register into FLASH
memory for storage. This process takes approximately 50 ms
and requires the power supply voltage to be within specification
for the duration of the event. It is worth noting that this
operation also automatically follows the auto null and factory
reset commands.
The DAC latch command loads the contents of AUX_DAC into
the DAC latches. Since the AUX_DAC contents must be
updated one byte at a time, this command ensures a stable DAC
output voltage during updates. Finally, the software reset
command sends the ADIS16250 digital processor into a restart
sequence, effectively doing the same thing as the RST line.
Table 13. COMMAND Register Definition
Address
0x3F, 0x3E
Table 14. COMMAND Bit Descriptions
Bit
15:8
7
6:4
3
2
1
0
Description
Not used
Software reset command
Not used
Manual FLASH update command
Auxiliary DAC data latch
Factory Calibration Restore command
Auto null command
Default
N/A
Format
N/A
ADIS16250
Access
Write only