L99LD20 datasheet(16/61 Pages) STMICROELECTRONICS

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Functional description

L99LD20

16/61

DS11366 Rev 3

3.1.2

Pre-standby mode

The device enters Pre-standby mode under the following conditions:

•

upon the two following consecutive SPI frames setting:

–

UNLOCK = 1

–

(EN, GOSTBY) = (0, 1)

The Pre-standby mode characteristics are:

•

V3V3 > VPOR

•

Bucks disabled

•

SPI active

The device leaves automatically Pre-standby mode entering standby:

•

if CSN High and DIN Low for a time t > tSTDBY

3.1.3

Reset mode

The device enters Reset mode under the following conditions:

•

By default, once the device leaves Standby mode;

•

If device state is Active mode, when one of the following events occur:

–VSPI under voltage;

–

Watchdog failure

–

One SPI frame setting (EN,GOSTBY) = (0,0)

–

Two consecutive SPI frames setting

UNLOCK = 1

(EN,GOSTBY) = (1,1)

The Reset mode characteristics are:

•

V3V3 > VPOR

•

All the control and status registers set to their default values

•

SPI inactive

The device leaves automatically Reset mode and enters Limp home after 400 ns (typical).

3.1.4

Limp home

The device enters Limp Home automatically 400 ns after Reset mode.

Limp home characteristics are:

•

Direct Input access enabled

•

Buck1 according DIN

•

Buck2 OFF

•

SPI active:

–

All SPI write operations must be allowed without any effects on the device

behavior.

When the device leaves this mode, it can enter Standby or Active mode.

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