1769205x2, 176881212, 176861512

FISM

– Fixed Isolated SMT Module

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Würth Elektronik eiSos GmbH & Co. KG

– Data Sheet Rev. 1.0

©July 2018

9/37

INTENDED USE

– Typical Application

Load

L

N

AC

“Reinforced Isolation“

uC

Bulk

Power Supply Unit (PSU)

Power Module (isolated)

Primary Circuit

Secondary Circuit (SELV Circuit)

Bridge

Rectifier

“Functional Isolation“

+

-

+

-

DC Bus

SELV

+VIN

-VIN

-VOUT

+VOUT

Module

2

1

4

5

+VIN

-VIN

-VOUT

+VOUT

standard. That requires that the power module is supplied by a SELV (safe extra low voltage) circuit which provides

protection against electric shock. There are no HAZARDOUS voltages present in CLASS III Equipment.

A SELV circuit is a secondary circuit

that is designed to be protected from excessive voltages (≥42 Vac or ≥ 60Vdc) during

normal operating conditions and single fault conditions. A reinforced isolation is required at the boundary between the

primary and the secondary circuit.

A circuit which has no direct connection to the primary circuit and derives its power from a transformer, converter or

equivalently isolated device, or a battery, is defined as a secondary circuit.

In accordance to the safety standard UL60950-1, functional isolation (insulation) is defined as:

“1.2.9.1 Functional Insulation: insulation that is necessary only for the correct functioning of the equipment

NOTE: Functional Insulation by definition does not protect against electric shock. It may, however, reduce the likelihood of

ignition and fire.”

“1.2.9.5 Reinforced Insulation: single insulation system that provides a degree of protection against electric shock equivalent

to Double Insulation under the conditions specified in this standard.

NOTE: The Term “insulation system” does not imply that the insulation has to be in one homogeneous piece. It may

comprise several layers that cannot be tested as Basic Insulation and Supplementary Insulation

ISOLATION VOLTAGE

To verify the integrity of an isolation a test voltage is applied for a specified time across a component that is designed to

provide electrical isolation. This test is known as a ‘Hi Pot Test’, ‘Flash Tested’, ‘Withstand Voltage’, ‘Proof Voltage’,

‘Dielectric Withstand Voltage’ & ‘Isolation Test Voltage’.

All isolated power modules are all 100% production tested at their stated isolation voltage. This is 2kVDC for 1 second.

The isolation test voltage indicated in this datasheet is for voltage transient immunity only. It does not allow this part to be

used within a safety isolation system.

The part will function properly with several hundreds of volts applied continuously across the isolation barrier, however

surrounding components must be individually analyzed to ensure proper insulation. Isolation measures are taken to prevent

any user-accessible circuitry from causing harm.