AN1441

Application information

Doc ID 8422 Rev 2

9/13

2

Application information

The ST890 application circuit needs few external components.

2.1

Power supply filtering

A 1 µF capacitor to GND can be placed at the input to reduce the drop voltage during

switching and short-circuit events. On the OUT pin to GND, a 100 nF capacitor filters the

output signal. For example, Figure 10 and 11 show the output voltage in a switching

condition, with a load-sinked current of 500 mA. In order to improve the performance of the

ST890, the filter capacitors should be placed near the pins.

2.2

PCB rules

Regarding the PCB (printed circuit board), some rules should be followed: the IN and OUT

pins should be connected using a large metal area to reduce the wire resistance and to

reduce the drop voltage between IN and OUT. The SET, FAULT and ON pins are not critical.

2.3

PCB thermal dissipation

Figure 12.

ST890 demonstration board (not to scale)

A ground plane is useful when improving the power dissipation of the ST890 device. In

normal conditions the package used for the ST890 device, the SO-8, can dissipate the

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the junction temperature. This temperature, which continually increases until the thermal

AM00169v1