FUNCTIONAL DESCRIPTION

The device has a common diagnostic output for

both channels which indicates open load in

on-state, open load in off-state, over temperature

From the falling edge of the input signal, the

status output, initially low

to signal a fault

condition

(overtemperature

or

open

load

on-state), will go back to a high state with a

different delay in case of overtemperature (tpovl)

and in case of open open load (tpol) respectively.

This feature allows to discriminate the nature of

the detected fault. To protect the device against

short circuit and over current condition, the

thermal protection turns the integrated Power

MOS off at a minimum junction temperature of

140

the switch is automatically turned on again. In

short circuit the protection reacts with virtually no

delay, the sensor (one for each channel) being

located inside each of the two Power MOS areas.

This positioning allows the device to operate with

one channel in automatic thermal cycling and the

other one on a normal load. An internal function

of the devices ensures the fast demagnetization

of -18V. This function allows to greatly reduces

the power dissipation according to the formula:

where f = switching frequency and

The maximum inductance which causes the chip

temperature to reach the shut-down temperature

in a specified thermal environment is a function of

according to the above formula. In this device if

exceeding 16V, both channel will switch off.

PROTECTING

THE

DEVICE

AGAINST

REVERSE

BATTERY

The simplest way to protect the device against a

continuous reverse battery voltage (-26V) is to

insert a Schottky diode between pin 2 (GND) and

ground, as shown in the typical application circuit

(fig. 2).

The consequences of the voltage drop across

this diode are as follows:

– If the input is pulled to power GND, a negative

thresholds and Vstat are increased by Vf with

respect to power GND).

– The undervoltage shutdown level is increa-

sed by Vf.

If there is no need for the control unit to handle

external analog signals referred to the power

GND, the best approach is to connect the

reference potential of the control unit

to the

device ground (see application circuit in fig. 3),

which becomes the common signal GND for the

diode.

Switching Time Waveforms

VND10B

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