Designing for Low Power and Estimating Battery Life for BLE Applications

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Document No. 001-92584 Rev. *A

22

Table 12. Connection Calculator Input Parameters

Based on the inputs, the sheet updates the average current in the blue cell.

4

BLE Applications

4.1

BLE System Power

A typical BLE application involves sending the sensor data from a BLE Peripheral device (such as a heart-rate

monitor) to a BLE Central device (such as a smartphone). The system-level architecture of a Peripheral device for

such applications has three major functional blocks, as shown in Figure 11: sensing, data and event processing, and

BLE connectivity. Each block contributes to the average current of the overall system.

4 . 1 . 1

S e n s i n g B l o c k

The sensing block comprises a sensor and transducer hardware that converts the sensor information into an analog

electrical signal, followed by a signal-conditioning circuit that is used for filtering and amplification of the analog

signal. The conditioned analog signal is converted into digital data for processing by an analog-to-digital converter

(ADC). The key factors that determine the current consumption in the sensing operation are the following:



Signal conditioning and analog-to-digital conversion: The signal-conditioning circuit and the ADC consume

significant current during the sensing operation.



Sampling rate: The sampling rate is the minimum rate at which the sensor data must be captured by the ADC to

have enough samples for accurate processing of the sensor data.



Scan rate: The scan rate is the rate at which a sensor must be polled to detect an activity. This allows the system

to be in low-power states if there is no activity.

Figure 11. System Block Diagram

Signal

Conditioning

ADC

CPU

Flash for

Data logging

+ processing

BLE

Connectivity

Sensor &

Transducer

Sensing

Table A - Input Parameters

Connection Settings (From BLE Component Configuration)

Value

Units

GAP Role

Peripheral

Connection Interval

1000

ms

Slave Latency

0

Number of bytes to be sent

0

System Settings

CPU clock (IMO) frequency

16

MHz

WCO clock accuracy

000_TO_020_PPM

ppm

Remote Device clock accuracy

000_TO_020_PPM

ppm

Transmit Power

0

dbm

Estimate Average Current Consumption

17.49

uA