OVERTEMPERATURE PROTECTION (OVT)

If the chip temperature exceeds

a central position in the chip) the chip deactivates

itself.

The following actions are taken:

• all the output stages are switched off;

• the signal DIAG is activated (active low).

Normal operation is resumed as soon as (typically

after some seconds) the chip temperature moni-

tored goes back below

The different thresholds with hysteretic behavior

assure that no intermittent conditions can be gen-

erated.

UNDERVOLTAGE PROTECTION (UV)

The supply voltage is expected to range from

9.5V to 35V, even if its reference value is consid-

ered to be 24V.

In this range the device operates correctly.

Below 9.5V the overall system has to be consid-

ered not reliable.

Consequently the supply voltage is monitored

continuously and a signal, called UV, is internally

generated and used.

The signal is “on” as long as the supply voltage

does not reach the upper internal threshold of the

signal disappears

Once the UV signal has been removed, the sup-

ply voltage must decrease below the lower

again.

mittent operation of the device at low supply volt-

ages that may have a superimposed ripple

around the average value.

The UV signal switches off the outputs, but has

no effect on the creation of the reference voltages

for the internal comparators, nor on the continu-

ous operation of the charge-pump circuits.

DIAGNOSTIC LOGIC

The situations that are monitored and signalled

with the DIAG output pin are:

• current limit (OVC) in action; there are 4 indi-

vidual current limiting circuits, one per each

output; they limit the current that can be sunk

from each output, to a typical value of

800mA, equal for all of them;

• under voltage (UV);

• over temperature protection (OVT).

The diagnostic signal is transmitted via an open

drain output (for ease of wired-or connection of

several such signals) and a low level represents

the presence of at least one of the monitored con-

ditions, mentioned above.

SHORT CIRCUIT OPERATION

In order to allow normal operation of the other in-

puts when one channel is in short cirtuit, an inno-

vative non dissipative over current protection (pat-

ent pending) is implemented in the device.

OUTPUT

CURRENT

Time

DIAG

(active low)

Time

Short Circuit

Short Circuit

Isc

Iout

D94IN105

Figure 2: Short Circuit Operation Waveforms

L6376

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