Designing for Low Power and Estimating Battery Life for BLE Applications

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Document No. 001-92584 Rev. *A

21

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

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

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.

Table A - Input Parameters

Advertisement Settings (From BLE Component Configuration)

Value

Units

Advertisement Type

Unconnectable Advertising

Advertisement Interval

1000

ms

Advertisement payload

14

bytes

System Settings

CPU clock (IMO) frequency

16

MHz

Transmit Power

0

dbm

Estimate Average Current Consumption

27.67

uA

Table B - Battery Life Estimator

hours of usage per day

24

hours

Battery Capacity

2200

mAh

Estimate Battery Life

3313

days