LLCC68 datasheet(67/106 Pages) SEMTECH

67 / 106 page

LLCC68

Data Sheet

Rev. 1.0

DS.LLCC68.W.APP

July 2019

67 of 106

Semtech

www.semtech.com

The SLEEP mode duration is defined by:

Sleep Duration = sleepPeriod * 15.625 µs

The RX mode duration is defined by

Rx Duration = rxPeriod * 15.625 µs

The following figure highlights operations being performed while in RxDutyCycle mode. It can be observed that the radio

will spend around 1 ms to save the context and go into SLEEP mode and then re-initialize the radio, lock the PLL and go into

RX. The delay is not accurate and may vary depending on the time needed for the XTAL to start, the PLL to lock, etc.

Figure 13-2: RX Duty Cycle Energy Profile

Upon preamble detection, the radio is set to look for a Sync Word (in GFSK) or a header (in LoRa®) and the timer is restarted

with a new value which is computed as 2 * rxPeriod + sleepPeriod. This is to ensure that the radio does not spend an

indefinite amount of time waiting in Rx for a packet which may never arrive (false preamble detection).

This implies a strong relationship between the time-on-air of the packet to be received, and the amount of time the radio

spends in RX and in SLEEP mode. If a long preamble is used on the TX side, care must be taken that the formula below is

respected:

Tpreamble + Theader ≤ 2 * rxPeriod + sleepPeriod

time

Radio Current

rxPeriod

sleepPeriod

500 us

Radio in SLEEP mode

Radio in RX mode

Radio in STDBY_RC

500 us

Radio in RX mode

LLCC68 데이터시트(PDF) 67 Page - Semtech Corporation