In this way, the temperature of the device is kept

enough low to prevent the intervention of the ther-

mal protection (in most of the cases) and so to

avoid the shut down of the whole device.

If a short circuit condition is present on one out-

put, the current limiting circuit puts that channel in

DELAY pin).

After that period, if the short circuit condition is

still present the output is turned off for another

pin).

When also this period is expired:

• if the short circuit condition is still present the

quence starts again;

• if the short circuit condition is not present

anymore the normal operation of the output

is resumed.

pendent and can be set from 64

µs to 15 ms, us-

ing external capacitors ranging from 50 pF to

15 nF (1.28

µs/pF).

If the OFF DELAY pin is tied to ground (i.e. the

The diagnostic output (DIAG) is active when the

output is switched off, while it is not active when

in that period a short circuit condition is present.

Typical waveforms for short circuit operation are

shown in figure 2.

If both the ON DELAY and the OFF DELAY pins

are grounded the non dissipative over current

protection is inhibited and the outputs in short cir-

cuit remain on until the thermal shutdown switch

off the whole device. In this case the short circuit

condition is not signalled by the DIAG pin (that

continues to signal the under voltage and over

temperature conditions).

PROGRAMMABLE DIAGNOSTIC DELAY

The current limiting circuits can be requested to

perform even in absence of a real fault condition,

for a short period, if the load is of capacitive na-

ture or if it is a filament lamp (that exhibits a very

low resistance during the initial heating phase).

To avoid the forwarding of misleading — i.e. short

diagnostic pulses in coincidence with the inter-

vention of the current limiting circuits when oper-

ating on capacitive loads — the activation of the

diagnostic can be delayed with respect to the in-

tervention of one of the current limiting circuits.

This delay can be defined by an external capaci-

and ground.

RESET INPUT

An external reset input R (pin 18) is provided to

simultaneously switch off all the outputs: this sig-

nal (active low) is in effect an asynchronous reset

that keeps the outputs low independently from the

input signals.

For example, this reset input can be used by the

CPU to keep the outputs low after a fault condi-

tion (signaled by the DIAG pin).

DEMAGNETIZATION OF INDUCTIVE LOADS

The device has four internal clamping diodes able

to demagnetize inductive loads.

The limitation is the peak power dissipation of the

packages, so — if the loads are big or if there is

the possibility to demagnetize more loads con-

temporarly — it is necessary to use external de-

magnetization circuits.

In figures 4 and 5 are shown two topologies for

the demagnetization versus ground and versus

The breakdown voltage of the external device

Vi

Vs

Vout

100mV

D94IN131

1.25V

100mV

Figure 3: Input Comparator Hysteresis

L6376

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