L9954TR datasheet(27/37 Pages) STMICROELECTRONICS

27 / 37 page

L9954 / L9954XP

Functional description of the SPI

Doc ID 14279 Rev 4

27/37

Table 19.

SPI - input data and status registers 1

Bit

Input register 1 (write)

Status register 1 (read)

Name

Comment

Name

Comment

Enable bit

If Enable bit is set the device

will be switched in active

mode. If Enable Bit is cleared

device goes into standby mode

and all bits are cleared. After

power-on reset device starts in

standby mode.

Always 1

A broken VCC-or SPI-

connection of the L9954

can be detected by the

microcontroller, because

all 24 bits low or high is

not a valid frame.

OUT6 OC

Recovery

Enable

In case of an over-current

event the over-current status

bit (Status Register 0) is set

and the output is switched off.

If the over-current Recovery

Enable bit is set the output will

be automatically reactivated

after a delay time resulting in a

PWM modulated current with a

programmable duty cycle (Bit

21 of Input Data Register 0).

Depending on occurrence of

Overcurrent Event and internal

clock phase it is possible that

one recovery cycle is executed

even if this bit is set to zero.

VS overvoltage

In case of an overvoltage

or undervoltage event

the corresponding bit is

set and the outputs are

deactivated. If Vs voltage

recovers to normal

operating conditions

outputs are reactivated

automatically.

x (don’t care)

VS undervoltage

OUT5 OC

Recovery

Enable

Thermal shutdown

In case of a thermal

shutdown all outputs are

switched off. The

microcontroller has to

clear the TSD bit by

setting the Reset Bit to

reactivate the outputs.

OUT4 OC

Recovery

Enable

Temperature

warning

The TW bit can be used

for thermal management

by the microcontroller to

avoid a thermal

shutdown. The

microcontroller has to

clear the TW bit.

x (don’t care)

Not ready bit

After switching the

device from standby

mode to active mode an

internal timer is started to

allow chargepump to

settle before the outputs

can be activated. This bit

is only present during

start up time.

Since this bit is

controlled by internal

clock it can be used for

synchronizing testing

events(e.g. measuring

filter times).

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