VNF1248F datasheet(26/79 Pages) STMICROELECTRONICS

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DIN input management

The device allows external FET control directly by hardware, through a dedicated input pin (DIN), in addition to

software control by the SPI interface. Through this pin, it is possible to turn-on/turn-off directly the power switch,

providing an alternative to application host management, as requested by safety requirements and by application

use cases in which the device could operate without the SPI interface being active. Clearly, DIN control is

superseded by faults occurrence.

On top of this functionality, DIN input is also used as an additional device wake up source from standby state and

as enable for capacitive charging mode functionality, if properly driven.

To fulfill different application requirements, DIN management can be configured by dedicated programmable

6.1

Standby state

As mentioned, a pulse on the DIN input, with duration > tDIN_WAKEUP, triggers the device wake-up (apart from the

FS_MODE = "01" configuration, where the DIN wake-up feature is disabled), allowing to move to the fail-safe

state with all relevant circuits enabled to allow external FET driving. No other DIN functions are available in this

state.

6.2

Unlocked state

In this state, DIN behavior is defined by the following control register fields:

•

DIN_CTRL_EN (CR#1): this bit enables the use of DIN input for output control; access to this control field

is managed by unlock sequence;

–

DIN_CTRL_EN = ‘0’ → DIN input not effective, output directly controlled only by OUTCTL bit

–

DIN_CTRL_EN = ‘1’ → DIN input control enabled

•

DIN_CTRL_OPT (CR#1): this bit defines the functional combination of DIN input with the correspondent

SPI-driven control bit (OUTCTL, CR#1); access to this control field is managed by the unlock sequence;

–

DIN_CTRL_OPT = ‘0’ → to turn ON external FET regardless of OUTCTL bit status; so-called OR

mode behavior, for example useful for quasi-synch turn-on in case of application with multiple

controllers and power switches sharing the same load

–

DIN_CTRL_OPT = ‘1’ → to turn OFF external FET regardless of OUTCTL bit status; so-called AND

mode behavior, for example useful for quasi-synch turn-off in case of application with multiple

controllers sharing the same load)

The table below shows possible combinations of DIN input with SPI-driven controls, depending on DIN control bit

configuration, and their effects on device outputs (power switch and diagnostic output) and internal blocks

(bypass switch); in case of bypass saturation detection (BYPASS_SAT fault), the power switch is automatically

turned on and bypass switched off, regardless of DIN/OUTCTL/BYPASSCTL status, to ensure proper driving of

load.

Table 24. Unlocked state - DIN control behavior

BYPASS_SAT

bit

DIN_CTRL_EN

bit

DIN_CTRL_OPT

bit

DIN

input

OUTCTL

bit

BYPASSCTL

bit

OUTPUT

BYPASS

Off

0/1

Off/On

Off

0/1

Off/On

VNF1248F

DIN input management

DS14109 - Rev 7

page 26/79

VNF1248F Datasheet(PDF) 26 Page - STMicroelectronics

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