BMC150 datasheet(20/141 Pages) ETC2

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Datasheet

eCompass BMC150

Page 20

Confidential

BST-BMC150-DS000-03 | Revision 0.4 | February 2013

Bosch Sensortec

third parties. BOSCH and the symbol are registered trademarks of Robert Bosch GmbH, Germany.

Note: Specifications within this document are subject to change without notice. Not intended for publication.

Figure 3 shows the timing diagram for low-power modes 1 and 2 when EDT is selected.

Figure 3: Timing Diagram for low-power mode ½, EDT

When (0x12) sleeptimer_en is set to ‘1’, the equidistant-sampling mode (EST) is selected. The

use of the EST mode is recommended when the FIFO is used since it ensures that equidistant

samples are sampled into the FIFO regardless of whether the active phase is extended by

active interrupt engines or interface activity. In EST mode the sleep time tSLEEP,a is defined as

shown in Figure 4. The FIFO sampling time tSAMPLE,a is the sum of the sleep time tSLEEP,a and the

sensor data sampling time tSSMP,a. Since interrupt engines can extend the active phase to

exceed the sleep time tSLEEP,a, equidistant sampling is only guaranteed if the bandwidth has

been chosen such that 1/(2 * bw) = n * tSLEEP,a where n is an integer. If this condition is infringed,

equidistant sampling is not possible. Once the sleep time has elapsed the device will store the

next available sample in the FIFO. This set-up condition is not recommended as it may result in

timing jitter.

Figure 4: Timing Diagram for low-power mode ½, EST

State

Sleep phase

Active phase

SLEEP

ACTIVE

State

Sleep phase

Active phase

SLEEP

SAMPLE

Sampled into FIFO

SSMP

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