AN92584 Datasheet, PDF (17/42 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
3.3.1
Note For advertising/connection intervals where the aperture is more than that supported by the instrument, a
different method is required to measure the average current. For example, the Keysight 34410A multimeter has a
maximum one-second aperture. Measuring the average current for intervals greater than one second requires a
different approach. For these cases, set the integration method on the instrument to Number of Power Line Cycles
(NPLC) and set the NPLC number to 100. Enable the “stats” option in the “math” menu. This will run an averaging
filter on the current samples measured. After allowing a few samples (approximately 100x interval time), the value
settles to a stable value, which is the average current.
Average Current in Advertising and Connection States
Table 8 and Table 9 list the average currents measured for different values of advertising and connection intervals
using the example projects. The remote device used is another BLE Pioneer Kit. You can also use the kit USB dongle
with the CySmart PC tool for connection-related measurements. The currents measured will be higher, however, due
to the higher WCO clock inaccuracy of the dongle WCO crystal.
Table 8. Advertising Interval Versus Average current
Advertising Interval (ms)
100
120
150
180
200
250
300
400
500
1000
4000
Current (µA)
261.8
219.5
175.6
147.0
132.3
106.4
88.8
66.5
53.3
26.6
7.5
Table 9. Connection Interval Versus Average Current
Connection Interval (ms)
10
20
30
40
50
60
70
80
90
100
200
300
400
500
Average Current (µA)
1501.3
783.6
522.7
389.0
313.4
264.2
224.9
197.3
175.4
157.2
80.3
53.9
41.0
33.2
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Document No. 001-92584 Rev. *A
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