ADIS16400/ADIS16405

Rev. B | Page 13 of 20

Magnetometer Soft-Iron Correction (Scale Factor)

The soft-iron correction factor for the magnetometer provides

the opportunity to change the scale factor for each individual axis.

Table 13. XMAGN_SIF, YMAGN_SIF, ZMAGN_SIF

Bits

Description

Default = 0x0800

[15:12]

Not used.

[11:0]

Data bits. Binary, linear scale adjustment factor

between 0x0000 (0x) and 0x3FFF (2x).

Gyroscope Automatic Bias Null Calibration

Set GLOB_CMD[0] = 1 (DIN = 0xBE01) to execute this function,

which measures the gyroscope outputs and then loads the gyro-

scope offset registers with the opposite values to provide a quick

bias calibration. Then, all sensor data resets to 0, and the flash

memory updates automatically within 50 ms (see Table 14).

Gyroscope Precision Automatic Bias Null Calibration

Set GLOB_CMD[4] = 1 (DIN = 0xBE10) to execute this function,

which takes the sensor offline for 30 sec while it collects a set of

gyroscope data and calculates a more accurate bias correction

factor for each gyroscope. Once calculated, the correction factor

loads into the three gyroscope offset registers, all sensor data

resets to 0, and the flash memory updates automatically within

50 ms (see Table 14).

Restoring Factory Calibration

Set GLOB_CMD[1] = 1 (DIN = 0xBE02) to execute this function,

which resets each user calibration register (see Table 10, Table 11,

and Figure 12) to 0x0000, resets all sensor data to 0, and auto-

matically updates the flash memory within 50 ms (see Table 14).

Linear Acceleration Bias Compensation (Gyroscope)

Set MSC_CTRL[7] = 1 (DIN = 0xB486) to enable correction for

low frequency acceleration influences on gyroscope bias. Note

that the DIN sequence also preserves the factory default condi-

tion for the data ready function (see Table 19).

OPERATIONAL CONTROL

Global Commands

The GLOB_CMD register provides trigger bits for several

useful functions. Setting the assigned bit to 1 starts each operation,

which returns to the bit to 0 after completion. For example, set

GLOB_CMD[7] = 1 (DIN = 0xBE80) to execute a software reset,

which stops the sensor operation and runs the device through

its start-up sequence. This includes loading the control registers

with their respective flash memory locations prior to producing

new data. Reading the GLOB_CMD registers (DIN = 0x3E00)

starts the burst mode read sequence.

Table 14. GLOB_CMD

Bits

Description

[15:8]

Not used

[7]

Software reset command

[6:5]

Not used

[4]

Precision autonull command

[3]

Flash update command

[2]

Auxiliary DAC data latch

[1]

Factory calibration restore command

[0]

Autonull command

Internal Sample Rate

The SMPL_PRD register provides discrete sample rate settings,

using the bit assignments in Table 15 and the following equation:

When SMPL_PRD[7:0] = 0x0A, the sample rate = 149 SPS.

Table 15. SMPL_PRD

Bits

Description

Default = 0x0001

[15:8]

Not used

[7]

0 = 0.61035 ms, 1 = 18.921 ms

[6:0]

The default sample rate setting of 819.2 SPS preserves the

sensor bandwidth and provides optimal performance. For

systems that value slower sample rates, simply read the device at

a slower rate and keep the internal sample rate at 819.2 SPS. Use

the programmable filter (SENS_AVG) to reduce the bandwidth

along with the reduced read rates. The data-ready function

(MSC_CTRL) can drive an interrupt routine that uses a counter to

help assure data coherence at the reduced update rates.

Power Management

Setting SMPL_PRD ≥ 0x0A also sets the sensor in low power

mode. For systems that require the lower power dissipation, in-

system characterization helps users to quantify the associated

performance trade-offs. In addition to sensor performance, this

mode affects SPI data rates (see Table 2). Set SLP_CNT[8] = 1

(DIN = 0xBB01) to start the indefinite sleep mode, which requires

a CS assertion (high to low), reset, or power cycle to wake up.

Use SLP_CNT[7:0] to put the device in sleep mode for a given

period of time. For example, SLP_CNT[7:0] = 0x64 (DIN =

0xBA64) puts the device to sleep for 50 seconds.

Table 16. SLP_CNT

Bits

Description

[15:9]

Not used

[8]

Indefinite sleep mode, set to 1

[7:0]

Programmable sleep time bits, 0.5 sec/LSB