VN06

Application information

13/17

3.1

Functional description

The device has a diagnostic output which indicates open load conditions in off state as well

diagnostic and output voltage level in normal operation and in fault conditions. The output

signals are processed by internal logic. The open load diagnostic output has a 5 ms filtering.

The filter gives a continuous signal for the fault condition after an initial delay of about 5 ms.

This means that a disconnection during normal operation, with a duration of less than 5 ms

does not affect the status output. Equally, any re-connection of less than 5 ms during a

disconnection duration does not affect the status output. No delay occur for the status to go

low in case of overtemperature conditions. From the falling edge of the input signal the

status output initially low in fault condition (over temperature or open load) will go back with

a delay (tpovl)in case of overtemperature condition and a delay (tpol) in case of open load.

These feature fully comply with International Standard Office (I.S.O.) requirement for

automotive High Side Driver. To protect the device against short circuit and over current

conditions, the thermal protection turns the integrated Power MOS off at a minimum junction

temperature of 140 oC. When the temperature returns to 125 oC the switch is automatically

turned on again. In short circuit the protection reacts with virtually no delay, the sensor being

located in the region of the die where the heat is generated. Driving inductive loads, an

internal function of the device ensures the fast demagnetization with a typical voltage

(Vdemag) of -18V. This function allows to greatly reduce the power dissipation according to

the formula:

Pdem = 0.5 ² Lload ² (Iload)2 ² [(VCC+Vdemag)/Vdemag] ² f where f =

switching frequency and Vdemag = demagnetization voltage Based on this formula it is

possible to know the value of inductance and/or current to avoid a thermal shutdown. The

maximum inductance which causes the chip temperature to reach the shutdown

temperature in a specific thermal environment, is infact a function of the load current for a

fixed VCC, Vdemag and f.

3.2

Protecting the device agaist load dump - test pulse 5

The device is able to withstand the test pulse No. 5 at level II (Vs = 46.5V) according to the

ISO T/R 7637/1 without any external component. This means that all functions of the device

are performed as designed after exposure to disturbance at level II. The VN03 is able to

withstand the test pulse No.5 at level III adding an external resistor of 150 ohm between pin

3.3

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 1 (GND) and ground, as shown in the typical

application circuit (Figure 9.). The consequences of the voltage drop across this diode are

as follows:

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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 node [1]

(see Figure 10.), which becomes the common signal GND for the whole control board

avoiding shift of Vih, Vil and Vstat. This solution allows the use of a standard diode.