L9963T datasheet(11/45 Pages) STMICROELECTRONICS

11 / 45 page

Figure 5. DIS pin structure

DIS

GND

CUT_DIG_IN

GND

V3V3_STBY

TO OPEN DRAIN OUTPUT

IN_PU

3.2.1.4

ISOFREQ

ISOFREQ pin is a digital input used to switch ISOline bit rate:

•

ISOFREQ = 1 selects fast operation: bit time is TBIT_LENGTH_FAST

•

ISOFREQ = 0 selects slow operation: bit time is TBIT_LENGTH_SLOW

ISOFREQ sampling depends on device state and configuration:

Table 9. ISOFREQ sampling strategy

L9963T

state

L9963T

configuration

ISOFREQ sampling

Note

Normal

state

Slave (NSLAVE =

The ISOFREQ pin is latched upon NCS assertion. Therefore, it

must be stable at least TISOFREQ_DEGLITCH + TISOFREQ_SETUP

before NCS assertion. Moreover, ISOFREQ must be kept stable

TISOFREQ_HOLD after NCS assertion in order to fulfil hold time

constraints.

The new bit rate setting is immediately applied to the RX

interface, while it is applied to the TX interface after the SPI

frame has been completely transmitted over the isolated SPI

interface. This allows Managing ISOFREQ And TXAMP Pins

For Communicating With L9963

In case several SPI

frames are being pushed

into the TX queue, the

setting applied once the

TX interface is in idle

depends on the last one

latched (no pipelining

supported).

Master (NSLAVE =

The ISOFREQ setting is simply resynchronized (TISOFREQ_SETUP

and TISOFREQ_HOLD requirements still apply) and deglitched

(TISOFREQ_DEGLITCH filter still present), but it is not latched upon

NCS assertion.

Stand-by

state

Slave/Master

(NSLAVE = X)

The new ISOFREQ setting is latched during the wake

up sequence. Hence, the ISOFREQ pin shall be stable

TISOFREQ_SETUP before the DIS high → low transition is applied

and shall not change during TWAKEUP.

Reset

state

Slave/Master

(NSLAVE = X)

The initial ISOFREQ setting is latched during the first power up

sequence. Hence, the ISOFREQ pin shall be stable before VDD

is applied and shall not change duringTFIRST_POWERUP.

The new bit rate of L9963T must be compatible with the one of all other units communicating on the same bus.

L9963T

Pin configuration

DS13590 - Rev 4

page 11/45

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