STCC02-ED5

10/13

Some basic rules can be applied to improve the STCC02 immunity in its application:

(1)

- The STCC02 is placed as close as possible of the MCU;

(2)

- The supply capacitors would increase the system immunity by being placed closed to the blocks they

feed;

(3)

- Wide supply copper plane should be avoided to reduce sensitivity to radiated interferences.

More specifically with the STCC02 circuit,

- A decoupling capacitor can be put on the STCC02 pins SYN and the MCU reset pin;

(4)

- Depending of the PCB layout quality, others capacitors may be put on sensitive pins such as the output

The power door switch is a well-identified electrical noise source for the electronic board. Its effect should

be reduced as much as possible. For instance, its power wires should be twisted together and split from

signal reward track should be linked to reduce EMI on the signal DS.

(5)

Standards such IEC61000-4-X evaluate the electro-

magnetic compatibility of appliance systems. To test

the immunity level of the STCC02 to the IEC61000-4-

4 (transient bursts), a board representative of usual

control unit for microwave oven has been developed,

as shown on top of page 11. One characteristics of

the IEC61000-4-4 test, is that no measurement

equipment can be connected to the tested system, as

it would corrupt the test results. That is why this board

includes a remote monitoring circuit based on optic

fibers. Thus, without any electrical link with an oscillo-

scope, it is possible to monitor the VDD voltage as

well as the RESET or the ZVS outputs of the

STCC02, during the IEC61000-4-4 test. This optical

link detects parasitic commutations of outputs as

short as 60ns.

With this board, and the burst generator coupled to the mains as specified in the IEC61000-4-4 standard

(see the above principle diagram), the STCC02 has been tested successfully at 4kV.

DOOR

SWITCH

RELAY

COIL

DS

Relay

Drive

5v REG

Reset

RST \

RST \

COM

MCU

STCC02

1

1

4

3

3

5

4

2

tr : 5 ns

tp : 50 ns

MAINS

0.5 kV to 4 kV

BURST COUPLE