si8405 Silicon Laboratories, si8405 Datasheet - Page 17

• Manufacturer Part Number: si8405
• Description: Bidirectional I 2c Isolators With Unidirectional Digital Channels
• Manufacturer: Silicon Laboratories

4. Layout Recommendations
Dielectric isolation is a set of specifications produced by safety regulatory agencies from around the world, which
describes the physical construction of electrical equipment that derives power from high-voltage power systems,
such as 100–240 V
specifications places a very high voltage between the input power pins of a product and the user circuits and the
user-touchable surfaces of the product. For the IEC relating to products deriving their power from the 220–240 V
power grids, the test voltage is 2500 V
There are two terms described in the safety specifications:


Figure 13 illustrates the accepted method of providing the proper creepage distance along the surface. For a
120 V
application, this distance is 6.4 mm, and a wide-body SOIC package must be used. There must be no copper
traces within this 3.2 or 6.4 mm exclusion area, and the surface should have a conformal coating, such as solder
resist. The digital isolator chip must straddle this exclusion area.
4.1. Supply Bypass
The Si84xx families require a 1 µF bypass capacitor between AVDD and AGND and BVDD and BGND. The
capacitor should be placed as close as possible to the package. See "6.Errata and Design Migration Guidelines"
on page 22 for more details.
Creepage—the distance along the insulating surface an arc may travel.
Clearance—the shortest distance through air that an arc may travel.
AC
application, this distance is 3.2 mm, and the narrow-body SOIC package can be used. For a 220–240 V
AC
systems or industrial power. The dielectric test (or HIPOT test) given in the safety
AC
Figure 13. Creepage Distance
(or 3750 V
Preliminary Rev. 0.1
IEC Specified
DC
Creepage
Distance
, the peak equivalent voltage).
Si840x
AC
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