An

Input

and

Asynchronous RESET,

both

TTL/CMOS compatible with wide voltage range

and high noise immunity (thanks to a built in hys-

teresis) are available.

OVER TEMPERATURE PROTECTION (OVT)

An on-chip Over Temperature Protection providse

an excellent protection of the device in extreme

conditions. Whenever the temperature - meas-

ured on a central portion of the chip- exceeds

Tmax=150 C (typical value) the device is shut off,

and the DIAG output goes LOW.

Normal operation is resumed as the chip tem-

perature (normally after few seconds) falls below

Tmax-Thys= 130 C (typical value). The hysteresis

avoid thats an intermittent behaviour take place.

UNDER VOLTAGE PROTECTION (UV)

The supply voltage is expected to range from 8 to

35 V. In this range the device operates correctly.

Below 8 V the overall system has to be consid-

ered not reliable. To avoid any misfunctioning the

supply voltage is continuously monitored to pro-

vide an under voltage protection. As Vs falls be-

low Vsth-Vshys (typically 7.5 V, see

fig.1) the

output power MOS is switched off and DIAG out-

put goes LOW. Normal operation is resumed as

soon as Vs exceeds Vsth. The hysteretic behav-

iour prevents intermittent operation at low supply

voltage.

OVER CURRENT OPERATION

In order to implement a short circuit protection the

output power MOS is driven in linear mode to limit

the output current to the Isc value. This Isc limit is

externally settable by means of an external 1/4 W

resistor connected from Rsc pin and GND. The

value of the resistor must be chosen according to

the following formula:

Isc (A) = 5/Rsc (kohm)

with

5 < Rsc < 30 (kohm)

For

Rsc < 5 (kohm)

Isc is limited to Isc=1.1 A (typical value).

This condition (current limited to the Isc value)

lasts for a Ton time interval, that can be set by

means of a capacitor (Cdon) connected to the ON

DELAY pin according to the following formula:

Ton = 1.28 msec/pF

for

50pF<Cdon< 2nF

After the Ton interval has expired the output

power MOS is switched off for the Toff time inter-

val with:

Toff = 64*Ton.

OUTPUT

CURRENT

Time

DIAG

(active low)

Time

Short Circuit

Short Circuit

Isc

Iout

D94IN105

Figure 3: Short Circuit Operation Waveforms

L6377

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