INPUT SECTION

The input section is an high impedance differen-

tial stage with high common and differential mode

range. There’s built-in offset of +1.4V (typical

value) and an hysteresis of 400mV (maximum

value), to ensure high noise immunity.

DIAGNOSTIC LOGIC

The operating conditions of the device are perma-

nently monitored and the following occurences

are signalled via the DIAG1/DIAG2 open-drain

output pins:

-Short Circuit versus ground.

A current limiting circuit fixes at Isc = 3.2A

(typical value) the maximum current that can

be sourced from the OUTPUT pin (for more

details see short circuit operation section).

- Short Circuit versus Vs.

- Under Voltage(UV)

- Over Temperature (OVT)

- Open Load, if the output current is less than

3mA (typical value).

- Output DMOS Open

according to the diagnostic Truth Table:

SHORT CIRCUIT OPERATION

in order to minimise the power dissipation when

the output is shorted to grounded, an innovative,

non dissipative short cicuit protection (patent

pending) is implemented, avoiding, thus the inter-

vention of the thermal protection in most cases.

Whenever the output is shorted to ground, or,

generally speaking, an over current is sinked by

the load, the output devices is driven in linear

mode, sourcing the Isc current (typically 3.2A) for

DELAY pin and GND. Whether the short circuit

status is not affected, acting as a Programmable

Diagnostic Delay.

This function allow the device to drive a capaci-

tive load or a filament lamp (that exhibits a very

low resistance during the initial heading phase)

without the intervention of the diagnostic.

the output DMOS is switched OFF and the DIAG2

condition is still present, the output DMOS is

turned ON (and the DIAG2 goes high - see fig4)

again, or, whether not, the normal condition op-

eration is resumed.

µs

tween 50pF and 2nF to have:

If the ON-DELAY pin is grounded the non dissipa-

tive short circuit protection is disabled, and the Isc

current is delivered until the Overtemperature

Protection shuts the device off. The behaviour of

the DIAG2 output is, in this situation, showed in

the Diagnostic Truth Table.

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 stage is switched off;

the signal DIAG2 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.

Protection will thus shut off the output whenever

the supply voltage falls below the mask fixed by

The hysteresis (see fig. 2) ensures a non intermit-

tent behavior at low supply voltage with a super-

imposed ripple.

The Under Voltage status is signalled via the

DIAG1 and DIAG2 outputs (see the Diagnostic

Truth Table) .

DEMAGNETIZATION OF INDUCTIVE LOADS

An internal zener diode, limiting the voltage

across the Power MOS to between 50 and 60V

inductive loads without external clamping devices.

The maximum energy that can be absorbed from

an inductive load is specified as 1J (at Tj = 85

°C)

(see figure 2)

L6370

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