Application information VND5004CSP30
18/28 DocID027938 Rev 3
3 Application information
Figure 22. Application schematic
3.1 MCUI/Os protection
When negative transients are present on the V
CC
line, the control pins will be pulled
negative to approximately -1.5V.
ST suggests the insertion of resistors (R
prot
) in the lines to prevent the μC I/Os pins from
latching up.
The values of these resistors provide a compromise between the leakage current of the μC,
the current required by the HSD I/Os (input levels compatibility) and the latch-up limit of the
μC I/Os.
-V
CCpeak
/I
latchup
d R
prot
d (V
OHμC
-V
IH
) / I
IHmax
Calculation example:
For V
CCpeak
= -1.5 V and I
latchup
t 20 mA; V
OHμC
t 4.5 V
75 ȍ d R
prot
d 240 kȍ.
Recommended values: R
prot
= 10 kȍC
EXT
=
10 nF
3.2 Load dump protection
D
ld
is necessary (Voltage Transient Suppressor) if the load dump peak voltage exceeds the
V
CCPK
max rating. The same applies if the device will be subject to transients on the V
CC
line that are greater than the ones shown in Table 11.
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