LLCC68 datasheet(31/111 Pages) SEMTECH

31 / 111 page

LLCC68

Data Sheet

Rev. 1.1

DS.LLCC68.W.APP

Dec 2024

31 of 111

Semtech

LLCC68

www.semtech.com

5. Power Distribution

5.1 Selecting DC-DC Converter or LDO Regulation

Two forms of voltage regulation (DC-DC buck converter or linear LDO regulator) are available depending upon the design priorities of the

application. The linear LDO regulator is always present in all modes but the transceiver uses DC-DC when selected. Alternatively a high

efficiency DC to DC buck converter can be enabled in FS, Rx and Tx modes.

The DC-DC can be driven by two clock sources:

• in STDBY_XOSC: RC13M supplies the clock and the frequency is RC13M / 4 so the switching frequency of the DC-DC converter is

3.25MHz

• in FS, RX, TX: the PLL supplies the clock and the frequency is ~5MHz; every time command SetRFFrequency(...) is called the

divider ratio is recalculated so that the switching frequency is as close as possible to the 5MHz target.

Unless specified, all specifications of the transceiver are given with the DC-DC regulator enabled. For applications where cost and size are

constrained, LDO-only operation is possible which negates the need for the 47nH inductor before pin 1 and the 15µH inductor between pins

7 and 9, conferring the benefits of a reduced bill of materials and reduced board space. The following table illustrates the power regulation

options for different modes and user settings.

The user can specify the use of DC-DC by using the command SetRegulatorMode(...). This operation must be carried out in STDBY_RC

mode only.

When the DC-DC is enabled, the LDO remains ON and its target voltage is set 50mV below the DC-DC voltage to ensure voltage stability for

high current peaks. If the DC-DC voltage drops to this level due to high current peak, the LDO covers for the current need at the expense of

the energy consumption of the radio which is increased.

However, to avoid consuming too much energy, the user is free to configure the Over Current Protection (OCP) register manually. At Reset,

the OCP is configured to limit the current at 140mA.

The OCP value is given on 6 bits, therefore the max OCP is 63 * 2.5mA = 157.5mA. It is configurable in steps of 2.5mA and the default value

is re-configured automatically each time the function SetPaConfig(...) is called. To adjust the OCP value, it is necessary to change the

Table 5-1: Regulation Type versus Circuit Mode

Circuit Mode

Sleep

STDBY_RC

STDBY_XOSC

Regulator Type = 0

LDO

Regulator Type = 1

LDO

DC-DC + LDO

Table 5-2: OCP Configuration

OCP default

Maximum Current

0x08E7

0x38

157.5mA

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