CALCULATION OF THECLAMPING VOLTAGE
USEOFTHEDYNAMICRESISTANCE
TheESDAfamilyhasbeen designed to clamp fast
spikes like ESD. Generally the PCB designers
need to calculate easily the clamping voltageV
CL
This is why we give the dynamic resistance in
addition to the classical parameters. The voltage
across the protection cell can be calculated with
thefollowingformula:
V
CL=VBR
+RdI
PP
WhereIppisthepeakcurrentthroughtheESDAcell.
DYNAMICRESISTANCEMEASUREMENT
Theshortdurationof the ESDhasled us toprefer
amoreadaptedtestwave,asbelowdefined,tothe
classical8/20µs and 10/1000µssurges.
I
Ipp
ESDA6V1S3 / ESDA6V2S6
As the value of the dynamic resistance remains
stable for a surge duration lower than 20µs, the
.
2.5µsrectangularsurgeis welladapted.Inaddition
bothrise and fall times are optimized to avoid any
parasiticphenomenonduring the measurementof
Rd.
2µs
tp = 2.5µs
2.5µsdurationmeasurementwave.
t
3/7
ESDA6V1S3 / ESDA6V2S6
Fig. 1
junctiontemperature.
: Peak power dissipation versus initial
Fig. 2 :
Peak pulse power versus exponential
pulseduration(Tj initial = 25 °C).
Ppp[Tj initial]/Pp[Tjinitial=25°C]
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0255075100125150
Tj initial(°C)
Fig. 3 : Clamping voltage versus peak pulse
current(Tj initial =25 °C).
Rectangularwaveformtp= 2.5 µs.
Ipp(A)
50.0
10.0
tp=2.5µs
Ppp(W)
2000
1000
100
10
110100
tp(µs)
Fig. 4: Capacitance versus reverse applied
voltage(typicalvalues).
2 - Protectionof symmetricalsignals.
Note: Capacitancevaluebetween any I/Opinand
Groundis dividedby2.
D1
D2
Dn
0to5V
0to5V
0to5V
A1
A2
A16
+/- 2.5 V
+/- 2. 5 V
+/- 2.5 V
ImplementingitsASD
TM
technology,SGS-Thomson
hasdevelopedamonolithicTRANSILdiodearray,
which is a reliable protection against electrostatic
overloads for computer I/O ports, modems, GSM
handsetsand accessoriesor othersimilar systems
with data outputs. The ESDAxxSx integrates 18
TRANSILdiodesin acompactpackagethat canbe
easily mounted close to the circuitry to be
protected,eliminatingtheassemblycosts
associated with the use of discrete diodes, and
alsoincreasingsystemreliability.
EachTRANSILhas abreakdownvoltage between
6.2V (minimum) and 7.2V (maximum). When the
inputvoltageis lower than the breakdown voltage,
the diodes present a high impedance to ground.
For short overvoltage pulses, the fast-acting
diodesprovide analmostinstantaneousresponse,
clampingthe voltageto a safe level.
Informationfurnished is believedto beaccurate andreliable. However, STMicroelectronics assumesno responsibilityfor the consequences of
use ofsuch informationnor forany infringementof patentsor otherrights ofthirdparties which mayresult fromits use. No license isgranted by
implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to
change withoutnotice. This publicationsupersedes and replaces all informationpreviouslysupplied.
STMicroelectronics products are not authorized for use as critical components in lifesupport devices or systems without express written approval of STMicroelectronics.
0.18g.
The ST logo is a registered trademarkof STMicroelectronics
1998STMicroelectronics - Printed in Italy - Allrightsreserved.
STMicroelectronics GROUP OF COMPANIES
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