ADIS16250

Rev. 0 | Page 15 of 20

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:

y = mx + b

where:

y = calibrated output data

x = precalibration data

m = sensitivity scale factor

b = offset scale factor

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

Default

Format

Access

0x11,

0x10

0.018315°/sec

0x0000

Twos

complement

R/W

Table 10. GYRO_OFF Bit Descriptions

Bit

Description

15:12

Not used

11:0

Data bits

Table 11. GYRO_SCALE Register Definition

Address

Format

Access

0x13, 0x12

0.0488%

0x0800

Binary

R/W

1 Scale is the weight of each LSB.

2 Equates to a scale factor of one.

Table 12. GYRO_SCALE Bit Descriptions

Bit

Description

15:12

Not used

11:0

Data bits

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

Default

Format

Access

0x3F, 0x3E

N/A

N/A

Write only

Table 14. COMMAND Bit Descriptions

Bit

Description

15:8

Not used

7

Software reset command

6:4

Not used

3

Manual FLASH update command

2

Auxiliary DAC data latch

1

Factory Calibration Restore command

0

Auto null command