L9679ETR datasheet(12/127 Pages) STMICROELECTRONICS

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5.2.1

Power-off mode

During the Power-off mode all supplies are disabled keeping the system in a quiescent state with very low current

draw from battery. As soon as VSAT>VSAT_ON the IC will move to Awake Mode.

5.2.2

Awake mode

During the Awake mode the VINT3V3 and CVDD internal regulators are turned on and once internal POR is

released and RESET_N pin is pulled high, the IC is ready for full activation of all the functionalities.

5.2.3

Active mode

When POR has been released and if VSAT stays above VSAT_ON threshold at least for TVSATFILT the device

enters Active mode.

In this state the internal regulators are not immediately switched off in case VSAT goes below VSAT_OFF

threshold. It’s necessary that VSAT stays below VSAT_OFF for at least TVSATFILT to disable internal

regulators.This filter time is present to avoid that glitch on VSAT supply can switch off the device. Anyway it must

be considered that, if VSAT goes down and output voltage of internal regulators cannot be sustained, the POR

signal will be asserted and the device is immediately switched off.

5.2.4

Power-up and power-down sequences

The typical behaviour of the IC during normal power-up and power-down is shown in Figure 4. Normal power-up

sequence and Figure 5. Normal power-down sequence.

It’s not required that the following sequence is applied. VSAT is the main supply of the device. VSYNC and VCC

supplies can be provided before or after VSAT and are necessary to guarantee the full functionality of the device.

L9679E

Start-up and power control

DS12485 - Rev 8

page 12/127

L9679ETR Datasheet(PDF) 12 Page - STMicroelectronics