VNF9D5F datasheet(13/108 Pages) STMICROELECTRONICS

13 / 108 page

Figure 6. Normal mode, short circuit - Programmable Blanking Window (PBW) < tD_RESTART

OT_FAULT

OTDIFF_DIAG

Iout

OT_DIAG

Latch Off delay→ fixed time window

Power Limitation

ILIMH

TPBW < TLOFF

Channel is latched off due to PBW function

Latch Off

PBW delay → time window related to parameter in CHLOFFTCR register

counter is active

3.3

Power limitation (PL)

If the difference between junction temperature and case temperature (ΔT = TJ - TC) rises above the power

limitation threshold ΔTPLIM, a power limitation event is detected.

The corresponding bit in the OUTSRx register - Channel Feedback Status bit (CHFBSR) - is set. The channel is

switched OFF and therefore the power limitation bit (TSD/PL, bit 4) in the Global Status Byte and the Global Error

Flag are set.

In normal mode, each output channel can be either set in latched OFF or time limited auto-restart operation in

case of a power limitation event.

•

In latched off operation: the output remains switched OFF until the difference between junction temperature

and case temperature (ΔT = TJ - TC) decreases below ΔTPLIMR. In order to restart the channel, the MCU

shall reset the latch-off event by refreshing the programmed value in the dedicated register

(CHLOFFTCR0). The action will clear the corresponding CHLOFFSR bit in the Output Status Register

OUTSRx and bit 4 (TSD/PL) in the Global Status Byte.

•

In time limited auto-restart: during the programmed time, the output is switched off as described and

switches on again automatically when the difference between junction temperature and case temperature

(ΔT = TJ - TC) decreases below ΔTPLIMR. In order to allow asynchronous diagnostic, the status bit is

latched during OFF-state of the channel and it is automatically cleared when the difference between

junction temperature and case temperature (ΔT = TJ - TC) decreases below ΔTPLIMRS. After the

programmed time has elapsed, the output remains switched OFF and acts as in latch-off mode.

•

In Fail Safe mode the channel works in auto-restart mode.

•

To improve the performances vs load compatibility test, ΔTJ value is set at 80°C for VCC < 17.5 V, whilst it

is set at 55 °C for VCC > 17.5 V.

•

In capacitive charge mode (CCM) ΔTJ value is set at 35°C.

3.4

Overload protection–Output current limitation (ILIMH)

In case of soft overload leading a channel to any output current level (including current limitation) with an output

voltage above the current sense shut down threshold, the programmed I²t curve will be still verified by the

implemented algorithm.

VNF9D5F

Protections

DS13946 - Rev 8

page 13/108

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