AN92584 Datasheet, PDF (21/42 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
3.4 Power Calculator
To make it easy to estimate the current consumption for your design, a power calculator based on an Excel
worksheet is provided with this application note. This tool allows you to calculate the average current consumption for
PSoC 4/PRoC BLE devices for the advertising and connection states of different system settings and BLESS
parameters. You can use this tool during the system design stage to derive the optimum set of parameters to achieve
the required low current consumption. Note that the calculator provides only an estimation of the current
consumption. The actual current measured in your system may be different depending on your system design and
how you use the various low-power modes.
The workbook has two calculators: the advertisement calculator and the connection calculator. In each calculator
sheet, the user input parameters are entered in the yellow cells provided in the Input Parameters table. The
calculated values are shown in the blue cells. The grey cells are for information purposes only. You are required to
edit only the yellow cells and not modify the other cells. The allowed range of values for each input parameter is
highlighted when you click on any input cell.
The advertisement calculator allows you to calculate the average current for different advertisement settings. The
advertisement calculator input parameters are shown in Table 10. Select the advertising type, interval, and size of the
data based on the configuration done in the BLE Component of your project. The CPU clock frequency can be 6,
12, or 16 MHz. You should also select the transmit power level configured in the BLE Component configuration.
Table 10. Advertisement Calculator Input Parameters
Table A - Input Parameters
Advertisement Settings (From BLE Component Configuration)
Value
Advertisement Type
Unconnectable Advertising
Advertisement Interval
1000
Advertisement payload
14
System Settings
CPU clock (IMO) frequency
16
Transmit Power
0
Estimate Average Current Consumption
27.67
Units
ms
bytes
MHz
dbm
uA
Based on the inputs, the sheet automatically updates the average current in the blue cell.
To estimate the battery life for an application such as iBeacon, where the device is in the Broadcaster role, select the
battery capacity and the number of hours in a day the device is active. It is assumed that for the rest of the time, the
device is in the OFF state and does not consume any power. Based on these inputs, the battery life is estimated, as
given in Table 11.
Table 11. Advertisement – Battery Life Calculation
Table B - Battery Life Estimator
hours of usage per day
Battery Capacity
Estimate Battery Life
24
2200
3313
hours
mAh
days
The connection calculator allows you to estimate the current consumption of a PSoC 4/PRoC BLE device in the
connection state in a Peripheral role. The connection calculator input parameters are shown in Table 12. Select the
connection interval and the slave latency based on the configuration done in the BLE Component of your project. The
CPU clock frequency can be 6, 12, or 16 MHz. You should also select the crystal clock accuracy of the WCO crystal
used in your design. The clock accuracy of the Central device, typically 031_TO_050_PPM, must also be entered.
The transmit power level configured in the BLE Component is also selected.
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Document No. 001-92584 Rev. *A
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