VN920SP-E datasheet(9/18 Pages) STMICROELECTRONICS

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VN920SP-E

Figure 8. Application Schematic

GND

PROTECTION

NETWORK

AGAINST

REVERSE BATTERY

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 dimension the

RGND resistor.

1) RGND ≤ 600mV / (IS(on)max).

2) 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’s datasheet.

Power Dissipation in RGND (when VCC<0: during reverse

battery situations) is:

PD= (-VCC)

2/RGND

This resistor can be shared amongst several different

HSD. 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

common with 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 the ST suggests to utilize Solution 2 (see

below).

Solution 2: A diode (DGND) in the ground line.

A resistor (RGND=1kΩ) 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 (j600mV) 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 line is also required to prevent

that, during battery voltage transient, the current exceeds

the Absolute Maximum Rating.

Safest configuration for unused INPUT pin is to leave it

unconnected, while unused SENSE pin has to be

connected to Ground pin.

LOAD DUMP PROTECTION

Dld is necessary (Voltage Transient Suppressor) if the

load dump peak voltage exceeds VCC max DC rating.

The same applies if the device will be subject to

transients on the VCC line that are greater than the ones

shown in the ISO T/R 7637/1 table.

µC I/Os 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

µC I/Os pins to latch-up.

The value of these resistors is a compromise between the

leakage current of

µC and the current required by the

HSD I/Os (Input levels compatibility) with the latch-up

limit of

µC I/Os.

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

Calculation example:

For VCCpeak= - 100V and Ilatchup ≥ 20mA; VOHµC ≥ 4.5V

Ω ≤ Rprot ≤ 65kΩ.

Recommended Rprot value is 10kΩ.

VCC

GND

OUTPUT

DGND

RGND

Dld

µC

+5V

Rprot

VGND

INPUT

CURRENT SENSE

RSENSE

Rprot

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