IMU-3000 INVENSENSE, IMU-3000 Datasheet - Page 19

• Manufacturer Part Number: IMU-3000
• Description: GYRO, TRI-AXIS, PROG +/-2000 DEG/S
• Manufacturer: INVENSENSE

Specifications of IMU-3000

• No. Of Axes: 3
• Sensor Case Style: QFN
• No. Of Pins: 24
• Supply Voltage Range: 2.1V To 3.6V
• Operating Temperature Range: -40°C To +85°C
• Interface: I2C, Serial
• Interface Type: I2C, Serial
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

6
6.1
The IMU-3000 has a flexible clocking scheme, allowing for a variety of internal or external clock sources for
the internal synchronous circuitry. This synchronous circuitry includes the signal conditioning and ADCs, the
DMP, and various control circuits and registers. An on-chip PLL provides flexibility in the allowable inputs for
generating this clock.
Which source to select for generating the internal synchronous clock depends on the availability of external
sources and the requirements for power consumption and clock accuracy. Most likely, these requirements
will vary by mode of operation. For example, in one mode, where the biggest concern is power consumption,
one may wish to operate the Digital Motion Processor of the IMU-3000 to process accelerometer data, while
keeping the gyros off. In this case, the internal relaxation oscillator is a good clock choice. However, in
another mode, where the gyros are active, selecting the gyros as the clock source provides for a more-
accurate clock source.
Clock accuracy is important, since timing errors directly affect the distance and angle calculations performed
by the Digital Motion Processor (or by extension, by any processor).
There are also start-up conditions to consider. When the IMU-3000 first starts up, the device operates off of
its internal clock, until programmed to operate from another source. This allows the user, for example, to
wait for the MEMS oscillators to stabilize before they are selected as the clock source.
6.2
In addition, the IMU-3000 provides a clock output, which allows the device to operate synchronously with an
external digital 3-axis accelerometer. Operating synchronously provides for higher-quality sensor fusion
data, since the sampling instant for the sensor data can be set to be coincident for all sensors.
6.3
The sensor data registers contain the latest gyro and temperature data. They are read-only registers, and
are accessed via the Serial Interface. Data from these registers may be read anytime, however, the interrupt
function may be used to determine when new data is available.
6.4
The IMU-3000 contains a 512-byte FIFO register that is accessible via the Serial Interface. The FIFO
configuration register determines what data goes into it, with possible choices being gyro data,
accelerometer data, temperature readings, and auxiliary ADC readings. A FIFO counter keeps track of how
many bytes of valid data are contained in the FIFO. The FIFO register supports burst reads. The interrupt
function may be used to determine when new data is available.
6.5
Interrupt functionality is configured via the Interrupt Configuration register.
include the INT pin configuration, the interrupt latching and clearing method, and triggers for the interrupt.
Items that can trigger an interrupt are (1) Clock generator locked to new reference oscillator (used when
switching clock sources); (2) Digital Motion Processor Done (programmable function); (3) new data is
available to be read (from the FIFO and Data registers); and (4) the IMU-3000 did not receive an
acknowledge from the accelerometer on the Secondary I
Interrupt Status register.
Allowable internal sources for generating the internal clock are:
•
•
Allowable external clocking sources are:
•
•
Clocking
Internal Clock Generation
Clock Output
Sensor Data Registers
FIFO
Interrupts
An internal relaxation oscillator
Any of the X, Y, or Z gyros (MEMS oscillators with a variation of ±1% over temperature range)
32.768kHz square wave
19.2MHz square wave
IMU-3000 Product Specification
19 of 56
2
C bus. The interrupt status can be read from the
Document Number: PS-IMU-3000A-00-01.1
Revision: 1.1
Release Date: 08/19/2010
Items that are configurable