AN92584 Datasheet, PDF (5/42 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
The WCO clock source must be ON to use the DEEPSLEEP mode to maintain the BLE link timing during the
DEEPSLEEP mode. The WCO may be turned OFF if BLE is not used or the BLESS DEEPSLEEP power mode is not
used.
The system can be in the Sleep or Active power modes during the BLESS SLEEP and ACTIVE power modes. It can
be put into the Deep-Sleep mode only when the BLESS is in the DEEPSLEEP mode and the BLESS link layer and
modem logic are not using the ECO clock. To ensure that invalid combinations of the system and BLESS modes are
not entered, the application should check the BLESS internal state first and then put the system into the appropriate
low-power mode.
2.4 Recommendations for Low Power
The user application should manage the system clocks, system power modes, and BLESS power modes to
implement a low-power design in PSoC 4/PRoC BLE devices.
The recommendations for implementing low-power designs (see Figure 2) are as follows:
 The BLESS should be put into the DEEPSLEEP mode between BLE events. The system should be put into the
Deep-Sleep mode during this time if there is no pending application processing.
 The system should be put into the Sleep mode when the BLESS is in the ACTIVE or SLEEP modes if no
application processing is required. The system can also be put into the Sleep mode when the BLESS is in the
CYBLE_BLESS_STATE_ECO_STABLE state.
 If the system is in the Sleep mode while the BLESS is in the ACTIVE or SLEEP modes, the ECO clock source
should be used for the CPU clock. This allows the IMO to be turned OFF to reduce current consumption.
 If the ECO is used in the system Sleep mode, the ECO clock should be divided down from 24 MHz to 3 MHz.
The 3-MHz frequency is enough to keep the system in the Sleep mode and switch back to the IMO clock when
the system exits the Sleep mode.
 The WCO must be selected with a low ppm variation. You should further tune it to reduce the ppm variation. A
lower ppm reduces the listening window time in the BLE Peripheral role, thus reducing the current consumed.
Refer to AN95089 – PSoC 4/PRoC BLE Crystal Oscillator Selection and Tuning Techniques for details on WCO
crystal tuning.
 If your application does not use the ILO, the ILO should be stopped to reduce current consumption.
Figure 2. Low-Power Implementation Recommendations
ECO Stable
ECO ON
Deep-Sleep
BLE Activity
BLE
Event
Active
Event Close
Deep-Sleep
Interval between BLE events
BLE
Event
Active or Sleep
Active or Deep-Sleep
Deep-Sleep
A
System Activity
Sleep
Active or Sleep
B
Deep-Sleep
A ^{Application pre-processing}
B _{Application post-processing}
ECO
WCO
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Document No. 001-92584 Rev. *A
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