L99LD20 datasheet(17/61 Pages) STMICROELECTRONICS

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DS11366 Rev 3

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L99LD20

Functional description

If the microcontroller sends to the device the following SPI frames sequence:

•

The first SPI frame sets UNLOCK bit = 1

(see bit <1> on Table 13: CR#1: Control Register 1)

•

The second consecutive SPI frame sets GOSTBY bit = 1 and EN bit = 0

(see bit <3> and bit <2> on Table 14: CR#2: Control Register 2)

The device enters Standby mode.

If the microcontroller sends to the device the sequence of the following SPI frames:

•

The first SPI frame sets UNLOCK bit = 1;

(see bit <1> on Table 13: CR#1: Control Register 1)

•

The second consecutive SPI frame sets GOSTBY bit = 0 and EN bit = 1.

(see bit <3> and bit <2> on Table 14: CR#2: Control Register 2)

The device enters Active mode.

In Limp Home, after setting bit 27 on GSB (FE1, functional error bit), an auto restart procedure

is implemented: every tAUTORESTART, functional error bit eventually set is automatically cleared.

3.1.5

Active mode

The device enters the Active mode if the microcontroller sends the following SPI frames

sequence:

•

In a first SPI frame set the UNLOCK bit to 1

(see bit <1> on Table 13: CR#1: Control Register 1)

•

In a second frame, set EN bit to 1 and GOSTBY bit to “0”

(see bit <2> and bit <3> on Table 14: CR#2: Control Register 2)

Table 2. Operating modes

Operating

mode

Entering conditions

Leaving condition

Characteristics

Standby

mode

– By default, once powered on (VS present);

– SPI active and micro sending following

consecutive frames:

UNLOCK = 1

(EN,GOSTBY) = (0,1)

DIN = High for tWAKEUP

and/or

CSN = Low for tWAKEUP

– V3V3 < VPOR;

–VS and VSPI low

consumption;

– SPI inactive

Pre-standby

mode

– Under the following conditions:

Two following consecutive SPI frames setting:

UNLOCK = 1

(EN,GOSTBY) = (0,1)

CSN High and DIN Low

for a time t > tSTDBY

– V3V3 > VPOR

– Bucks disabled

– SPI active

Reset mode

– By default, when device leaves Standby mode

– Under following condition, when device is in

Active mode:

VSPI Under voltage

WD failure;

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

Two consecutive SPI frames setting:

UNLOCK = 1

(EN,GOSTBY) = (1,1)

Automatic transition after

400 ns

– All registers reset to

default values

– V3V3>VPOR

– SPI inactive

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