AN92584 Datasheet, PDF (31/42 Pages) Ramtron International Corporation – Designing for Low Power and Estimating Battery Life for BLE Applications

Designing for Low Power and Estimating Battery Life for BLE Applications
 Active state: The Active state denotes that all the scanning and processing activities are carried out at the
highest required rate. Typically, the trackpad scan is done every 10 ms in the Active state. Therefore, most of the
current consumption of the system originates in the Active state. The firmware will remain in the Active state as
long as user activities are happening.
 Idle state: When using the trackpad, users may keep the trackpad idle for several seconds between touch
activities. The Idle state saves power when the trackpad in not being used for an idle period. This state is entered
if no touch activity is detected for a specified timeout in the Active state. In this state, the trackpad is scanned at
a rate lower than needed for a smooth mouse movement, but sufficient to detect the start of a touch activity
without an observable delay. The BLE connection uses slave latency to reduce the use of the radio, while
maintaining readiness to send the data without latency when a user activity is detected. The system and BLESS
are in the Deep-Sleep mode for most of the time.
 Low-Power state: The system is expected to stay in the low-power state for most of the time. The application
enters this state from the Idle state if a user activity is not detected during the Idle state for additional time. In this
state, a BLE connection is sustained with no application data exchange. The application may also increase the
slave latency to reduce the use of the radio while sustaining the connection. The trackpad still needs to be
scanned to detect user activity. To detect a touch activity, a high resolution of the touch is not needed. Therefore,
only the alternate rows of the trackpad are scanned. The system is in the Deep-Sleep mode for most of the time.
 Shutdown state: When the battery voltage drops below the operable voltage, the system stops all the activities
and shuts down. This is done by putting the system in the Hibernate or Stop mode.
It should be noted that in each of these states, the system undergoes power mode transitions among the Deep-
Sleep, Sleep, and Active modes for optimizing power, based on the device activity. Only the durations for which the
device remains in the Active or Deep-Sleep mode are different in different states.
4.6 Implementing System Design Recommendations
4.6.1
RF Transmit Power
RF transmit power can be reduced to conserve power. To configure the RF transmit power in your project, open the
Configure BLE window from the BLE Component instance, as shown in Figure 19.
1. Go to the GAP Settings tab.
2. Configure the TX power level (dBm) to the desired setting from the list.
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Document No. 001-92584 Rev. *A
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