User's Manual

Table Of Contents

Battery Life Calculation

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3.2 Battery Life Calculation

For battery life calculations, it is highly recommended that the customer reviews CC2541 Battery Life

Calculation, SWRA347.

It is impossible to use a single metric to compare the power consumption of a BLE device to another

device. For example, a device gets rated by its peak current. While the peak current plays a part in the

total power consumption, a device running the BLE stack only consumes current at the peak level during

transmission. Even in very high throughput systems, a BLE device is only transmitting for a small

percentage of the total time that the device is connected (see Figure 3-4).

Figure 3-4. Current Consumption

In addition to transmitting, there are other factors to consider when calculating battery life. A BLE device

can go through several other states, such as receiving, sleeping, and waking-up from sleep. Even if the

current consumption of a device in each different state is known, there is not enough information to

determine the total power consumed by the device. Each layer of the BLE stack requires a certain amount

of processing to remain connected and to comply with the specifications of the protocol. The MCU takes

time to perform this processing, and during this time, current is consumed by the device. In addition, some

power might be consumed while the device switches between states (see Figure 3-5). All of this must be

considered in order to get an accurate measurement of the total current consumed.

Figure 3-5. Current Consumption-Active vs Sleep Modes

Hardware Description SNOA922–April 2013

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