VNQ830

Application information

Doc ID 7390 Rev 5

19/28

where -IGND is the DC reverse ground pin current and can be found in the absolute

maximum rating section of the device datasheet.

Power dissipation in RGND (when VCC < 0 during reverse battery situations) is:

PD = (-VCC)

2/ R

GND

This resistor can be shared amongst several different HSDs. Please note that the value of

this resistor should be calculated with formula (1) where IS(on)max becomes the sum of the

maximum on-state currents of the different devices.

Please note that, if the microprocessor ground is not shared by the device ground, then the

RGND will produce a shift (IS(on)max * RGND) in the input thresholds and the status output

values. This shift will vary depending on how many devices are ON in the case of several

high side drivers sharing the same RGND .

If the calculated power dissipation requires the use of a large resistor, or several devices

have to share the same resistor, then ST suggests using solution 2 below.

3.1.2

Solution 2: a diode (DGND) in the ground line

A resistor (RGND = 1 kΩ) should be inserted in parallel to DGND if the device will be driving

an inductive load. This small signal diode can be safely shared amongst several different

HSD. Also in this case, the presence of the ground network will produce a shift (

≈600 mV) in

the input threshold and the status output values if the microprocessor ground is not common

with the device ground. This shift will not vary if more than one HSD shares the same

diode/resistor network. Series resistor in INPUT and STATUS lines are also required to

prevent that, during battery voltage transient, the current exceeds the Absolute Maximum

Rating. Safest configuration for unused INPUT and STATUS pin is to leave them

unconnected.

3.2

Load dump protection

Dld is necessary (voltage transient suppressor) if the load dump peak voltage exceeds the

VCC maximum DC rating. The same applies if the device is subject to transients on the VCC

line that are greater than those shown in the ISO T/R 7637/1 table.

3.3

MCU I/O protection

If a ground protection network is used and negative transients are present on the VCC line,

the control pins will be pulled negative. ST suggests to insert a resistor (Rprot) in line to

prevent the microcontroller I/O pins from latching up.

The value of these resistors is a compromise between the leakage current of microcontroller

and the current required by the HSD I/Os (Input levels compatibility) with the latch-up limit

microcontroller I/Os:

-VCCpeak / Ilatchup ≤ Rprot ≤ (VOHμC - VIH - VGND) / IIHmax

Obsolete

Product(s)

- Obsolete

Product(s)