VN800S datasheet(7/22 Pages) STMICROELECTRONICS

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VN800S / VN800PT

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/R

GND

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 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 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.

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

µC I/Os.

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

Calculation example:

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

Ω ≤ R

prot ≤ 65kΩ.

Recommended Rprot value is 10kΩ.

APPLICATION SCHEMATIC

VCC

INPUTn

GND

STATUSn

OUTPUTn

Volt.

Reg

BUS

ASIC

24VDC

VCC

DGND

VGND

RGND

Rprot

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