The MKW2x IEEE 802.15.4 series devices have a unique feature for that saves power during the receive sequence of the transceiver. The feature is called Low Power Preamble Search (LPPS). When the LPPS feature is enabled, the demodulator section of the receiver is duty cycled during part of the preamble search phase of packet reception. During the LPPS phase of the preamble, the receiver looks for one symbol 0 match. Once this criterion for LPPS is met the receiver goes into normal preamble search followed by packet processing. The hardware sequence manager handles the timing and is not adjustable by the user. During LPPS mode, the receiver current consumption is reduced approximately 4mA. In addition, there is no added cost of using the LPPS feature since no extra components are required. In fact, enabling LPPS mode all the time has little system design impact and the current savings is 20%.
LPPS Flow and timing diagram:
The following figures show the MKW2x LPPS flow diagram and timing associated with the feature. Although not adjustable by the user, it figures show the hardware sequence of the feature.
Figure 1: LPPS Flow Diagram
Figure 2: LPPS Timing
More infomation about the LPPS feature can be found in the MKW2x device reference manual located at : KW2x |Kinetis KW2x 2.4 GHz RF MCUs|Freescale