MODES OF OPERATION
The sensor has three power modes: Off Mode, Standby Mode, and Active Mode to offer the customer different power
consumption options. The sensor is only capable of running in one of these modes at a time.
The Off Mode offers the lowest power consumption, approximately 0.4 µA and can only be reached by powering down the
analog supply. See
In this mode, there is no analog supply and all I
2
C activity is ignored.
The Standby Mode is ideal for battery operated products. When Standby Mode is active the device outputs are turned off
providing a significant reduction in operating current. When the device is in Standby Mode the current will be reduced to
approximately 3 µA. Standby Mode is entered as soon as both analog and digital power supplies are up. In this mode, the device
can read and write to the registers with I
2
C, but no new measurements can be taken. The mode of the device is controlled through
the MODE (0x07) control register by accessing the mode bit in the Mode register.
During the Active Mode, continuous measurement on all three axes is enabled. In addition, the user can choose to enable:
Shake Detection, Tap Detection, Orientation Detection, and/or Auto-Wake/Sleep Feature and in this mode the digital analysis for
any of these functions is done. The user can configure the samples per second to any of the following: 1 sample/second,
2 samples/second, 4 samples/second, 8 samples/second, 16 samples/second, 32 samples/second, 64 samples/second, and
120 samples/second, for the Auto-Sleep state. If the user is configuring the Auto-Wake feature, the selectable ranges are:
1 sample/second, 8 samples/second, 16 samples/seconds and 32 samples/second. Depending on the samples per second
selected the power consumption will vary.
Table 5. Modes Of Operation
Measurement and
Power Mode
Power Down
Mode
I²C Bus
DVDD is down, so I
2
C bus
cannot
be
used for other devices (MMA7660FC
clamps I
2
C bus to DVVD pin)
DVDD AVDD
Off
Off
Off
On
Function
MMA7660FC is powered down in both supplies. I
2
C activity is
unavailable on bus.
MMA7660FC is powered down in digital supply but not analog
supply. I
2
C activity is unavailable on bus. AVDD power cycling
requires 50 msec.
Off Mode
MMA7660FC will not respond, but I
2
C
bus can be used for other devices
(MMA7660FC does not load I
2
C bus)
MMA7660FC will respond to I
2
C bus
On
Off
MMA7660FC is powered down in analog supply but not digital
supply. I
2
C activity is ignored.
On
On
MMA7660FC is powered up in both supplies, so registers can be
accessed normally to set MMA7660FC to Active Mode when
desired. MMA7660FC's sensor measurement system is idle.
MMA7660FC is able to operate sensor measurement system at
user programmable samples per second and run all of the digital
analysis functions. Tap detection operates in Active Mode and
Auto-Sleep, but not Auto-Wake.
Standby Mode
Active Mode
Auto-Sleep
Auto-Wake
MMA7660FC will respond to I
2
C bus
On
On
Figure 5. State Machine of Modes
MMA7660FC
Sensors
Freescale Semiconductor
10
FREESCALE [ FREESCALE SEMICONDUCTOR, INC ]
