AN92584 Datasheet, PDF (22/42 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
Table 12. Connection Calculator Input Parameters
Table A - Input Parameters
Connection Settings (From BLE Component Configuration)
GAP Role
Connection Interval
Slave Latency
Number of bytes to be sent
System Settings
CPU clock (IMO) frequency
WCO clock accuracy
Remote Device clock accuracy
Transmit Power
Estimate Average Current Consumption
Value
Peripheral
1000
0
0
16
000_TO_020_PPM
000_TO_020_PPM
0
17.49
Based on the inputs, the sheet updates the average current in the blue cell.
Units
ms
MHz
ppm
ppm
dbm
uA
4 BLE Applications
4.1
4.1.1
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.
Sensing Block
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
Sensing
Flash for
Data logging
+ processing
Sensor &
Transducer
Signal
Conditioning
ADC
CPU
BLE
Connectivity
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Document No. 001-92584 Rev. *A
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