Sensors

Freescale Semiconductor, Inc.

10

MMA7660FC

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

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

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.

Figure 5. State Machine of Modes

Table 5. Modes Of Operation

Measurement and

Power Mode

I²C Bus

DVDD AVDD

Function

Power Down

Mode

used for other devices (MMA7660FC

Off

Off

unavailable on bus.

Off

On

MMA7660FC is powered down in digital supply but not analog

requires 50 msec.

Off Mode

bus can be used for other devices

On

Off

MMA7660FC is powered down in analog supply but not digital

Standby Mode

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.

Active Mode

Auto-Sleep

Auto-Wake

On

On

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.