S2-LPS datasheet(35/73 Pages) STMICROELECTRONICS

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Operating modes

The S2-LPS is provided with a built-in main controller which controls the switching between the two main

operating modes: transmitter (TX) and receiver (RX), driven by SPI commands.

In shutdown condition (the S2-LPS can be switched on/off with the external pin SDN), no internal supply is

generated, and all stored data and configurations are lost.

From shutdown, the S2-LPS can be switched on going to READY state, where the reference clock signal is

available.

From READY state, the S2-LPS can be moved to LOCK state to generate the high precision LO signal and then

in TX or RX modes. Switching from RX to TX and vice versa can happen only by passing through the LOCK

state. This operation is managed by the main controller through a single user command (TX or RX). At the end

of the operations, the S2-LPS can return to READY state or can go to SLEEP state, having a very low power

consumption.

SLEEP state can be configured to retain the FIFOs content or not enabling very low power mode. If also no

wake-up timer is required, the S2-LPS can be moved from READY to STANDBY state, which has the lowest

possible current consumption.

Figure 12. State diagram

Three states: READY, STANDBY and LOCK may be defined as stable state.

All other states are transient, which means that, in a typical configuration, the controller remains in those states,

at most for any timeout timer duration. Also the READY and LOCK states behave as transients when they are not

directly accessed with the specific commands (for example, when LOCK is temporarily used before reaching the

TX or RX states).

Table 41. States

State code(1)

State name

Digital LDO

SPI

XTAL

RF synth.

Wake-up timer

SHUTDOWN

OFF

Off

0x02

STANDBY

Off

S2-LPS

Operating modes

DS13831 - Rev 1

page 35/73

S2-LPS 데이터시트(PDF) 35 Page - STMicroelectronics