10.4.2. Safety. Silicon Laboratories Si2493, Si2404, Si2415, Si2434, Si2494, Si2439, Si2457, Si2443

AN93

10.4.2. Safety

Designs using the ISOmodem pass all overcurrent and overvoltage tests for UL1950 3rd Edition with the addition

of a 1.25 A Fuse or PTC, as shown in Figure 50. In a cost-optimized design, compliance to UL1950 does not

always require overvoltage tests. In the design cycle, it is important to plan ahead and know which overvoltage tests will apply. System-level elements in the construction, such as fire enclosure or spacing requirements, need to be considered during the design stages. Consult with a testing agency during product design to determine which tests will apply.

1000

 @ 100 MHz, 200 mA

C8

FB1

1.25 A

TIP

Fuse/PTC

RV1

1000

 @ 100 MHz, 200 mA

FB2

RING

C9

Figure 50. Circuits that Pass All UL1950 Overvoltage Tests

10.4.3. Surges

Use the reference design described in "4. Hardware Design Reference" on page 46 with through-hole Y1

capacitors for C1, C2, C8, and C9. Use spacing between the capacitor leads, between any line-side (high voltage) component or trace and system side (low voltage) component or trace greater than 8 mm. Also, the spacing between any line-side component or trace (or through-hole lead extending through the PCB) and the chassis (or anything connected to the chassis or low voltage circuitry) must be greater than 8 mm or protected with insulating material capable of withstanding a voltage greater than 8 kV. Additionally, slots cut through the PCB are recommended between the leads of C1, C2, C8, and C9 for increased creepage. The PCB and components should be clean and free of contamination, such as solder flux or other residue. The design engineer must verify the spacing indicated above meets or exceeds any specifications with which they wish to comply. The ISOmodem, used with the components and techniques described above, offers the highest reliability and lowest cost of any available solution. The use of supplemental surge-suppression components is not recommended.

Rev. 1.41

267