L9678P datasheet(21/203 Pages) STMICROELECTRONICS

21 / 203 page

DocID029274 Rev 3

21/203

L9678P, L9678P-S

Start-up power control

202

4.2.1

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 WAKEUP > WU_mon the IC will move

to Sleep mode.

4.2.2

Sleep mode

During the Sleep mode the VINT3V3 and CVDD internal regulators are turned on and the IC

is ready for full activation of all the other supplies. As soon as battery voltage is over a

minimum threshold, all the other supplies are turned on and the IC enters the Active mode.

4.2.3

Active mode

This is the normal operating mode for the system.

All power supplies are enabled and the energy reserve boost converter starts to increase

the voltage at ERBOOST. Likewise, the VDD5 regulator is turned on. Once the VDD5 has

reached a good value, the VDD3V3 regulator starts up. Once the VDD3V3 regulator is in

regulation, RESET is released allowing the system microcontroller and other components to

begin their power-on sequence. Among these, also the ER charge current generator can be

enabled by the microcontroller via a dedicated SPI command.

The active mode can be left when either WAKEUP pin or VIN voltage drop down. For the

very first 9 ms after having entered the active mode, the WAKEUP pin low would

immediately cause the IC to switch back to sleep mode. After that time, WAKEUP pin low

must be first confirmed by a MCUSPI_SLEEP command prior to cause the system to switch

to passive mode. Passive mode is also entered in case of VIN voltage low.

4.2.4

Passive mode

In this state, the energy reserve charge current is disabled and the ERBOOST boost

converter is disabled only if the SYS_CFG(KEEP_ERBST_ON)=0. When in passive mode

the device automatically activates both the COVRACT output pin and the integrated ER

switch to allow VIN to be connected to the ER capacitor. In this time, VIN is supposed to be

increased up to almost VER level and the system operation relies on energy from the ER

capacitor. Two scenarios are possible: high or low battery. If VIN < VINGOOD, the device

moved from RUN state in ACTIVE mode to the ER state. Here, the ER capacitor is depleted

while supplying all the regulators until the POR on internal regulator occurs. The threshold

to decide the ER switch activation is based on VIN, because VIN is the supply voltage rail

for all regulators. If the device has still a good battery level, it entered the POWERMODE

SHUTDOWN thanks to WAKEUP pin and MCU command to switch off. In this case, the

VER node will be discharged down to approximately VIN level, which then will be supplied

out of the battery line. System will continue to run up to a dedicated SPI command which will

lead the device to enter the POWEROFF state.

The wake-up pin is filtered to suppress undesired state changes resulting from transients or

glitches. Typical conditions are shown in the chart below and summarized by state.

L9678P 数据表(PDF) 21 Page - STMicroelectronics

L9678P 数据表(HTML) 21 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载