LLCC68 datasheet(52/106 Pages) SEMTECH

52 / 106 page

LLCC68

Data Sheet

Rev. 1.0

DS.LLCC68.W.APP

July 2019

52 of 106

Semtech

www.semtech.com

In case of POR or when the device is recovering from Sleep mode in cold start mode, the image calibration is performed as

part of the initial calibration process and for optimal image rejection in the band 902 - 928 MHz. However at this stage the

internal state machine has no information whether an XTAL or a TCXO is fitted. When the 32 MHz clock is coming from a

TCXO, the calibration will fail and the user should request a complete calibration after calling the function

SetDIO3AsTcxoCtrl(...).

By default, the image calibration is made in the band 902 - 928 MHz. Nevertheless, it is possible to request the device to

perform a new image calibration at other frequencies.

Note:

Contact your Semtech representative for the other optimal calibration settings outside of the given frequency bands.

9.3 Sleep Mode

In this mode, most of the radio internal blocks are powered down or in low power mode and optionally the RC64k clock

and the timer are running. The chip may enter this mode from STDBY_RC and can leave the SLEEP mode if one of the

following events occurs:

•

NSS pin goes low in any case

•

RTC timer generates an End-Of-Count (corresponding to Listen mode)

When the radio is in Sleep mode, the BUSY pin is held high.

9.4 Standby (STDBY) Mode

In standby mode the host should configure the chip before going to RX or TX modes. By default in this state, the system is

clocked by the 13 MHz RC oscillator to reduce power consumption (in all other modes except SLEEP the XTAL is turned ON).

However if the application is time critical, the XOSC block can be turned or left ON.

XOSC or RC13M selection in standby mode is determined by mode parameter in the command SetStandby(...).

The mode where only RC13M is used is called STDBY_RC and the one with XOSC ON is called STDBY_XOSC.

If DC-DC is to be used, the selection should be made while the circuit is in STDBY_RC mode by using the

SetRegulatorMode(...) command, then the DC-DC will automatically switch ON when entering STDBY_XOSC mode. The

DC-DC will be clocked by the RC13M. The LDO will remain active with a target voltage 50 mV lower than the DC-DC one.

Table 9-2: Image Calibration Over the ISM Bands

Frequency Band [MHz]

Freq1

Freq2

430 - 440

0x6B

0x6F

470 - 510

0x75

0x81

779 - 787

0xC1

0xC5

863 - 870

0xD7

0xDB

902 - 928

0xE1 (default)

0xE9 (default)

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