VN820 datasheet(18/43 Pages) STMICROELECTRONICS

18 / 43 page

Application information

VN820

18/43

Doc ID 7370 Rev. 6

Application information

Figure 24.

Application schematic

3.1

GND protection network against reverse battery

3.1.1

Solution 1: resistor in the ground line (RGND only)

This can be used with any type of load.

The following is an indication on how to size the RGND resistor.

RGND ≤ 600 mV / (IS(on)max)

RGND ≥ (- VCC) / (- IGND)

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 leads to a large resistor or several devices have to share

the same resistor then ST suggests to utilize Solution 2 (see below).

VCC

GND

OUTPUT

DGND

RGND

Dld

μC

+5V

Rprot

VGND

STATUS

INPUT

+5V

Rprot

Obsolete

Product(s)

- Obsolete

Product(s)

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