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AN2208

2 VN808 reference design board

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VN808 reference design board

This is a practical example how the VN808 high-side driver (HSD) can be used in applications

for an industrial environment.

2.1

Circuit description

In order to protect the high-side driver (HSD) from the harsh industrial conditions of power

supply lines, usually optocouplers and Transil diodes are used to separate the application

control circuits from the power supply. Figure 11 shows a complete schematic diagram of the

VN808 reference design board.

The VN808 reference design board uses multi-channel TLP281-4 and TLP181 optocouplers.

The TLP281-4 and TLP181 are small and thin couplers, suitable for surface-mounted

assemblies that consist of a photo transistor optically coupled to a gallium-arsenide infrared

emitting diode. The isolation voltage for this type of optocoupler is 2500 VRMS.

The clamping function of Transil diodes protect the HSD against transient overvoltages. The

reference design board is assembled with uni-directional SM15TXXA Transil diodes because

they protect the HSD against both positive and negative surge pulses. For more information

about SM15TXXA Transil diodes from STMicroelectronics, please refer to the SM15T36A

Datasheet available at www.st.com.

Refer to Section A.2: Recommended VN808 PCB Layout on page 43 for more information

about designing boards to improve EMC immunity and performance in industrial environments.

2.2

Surge suppression

When designing your application, VCC and ground lines should lay on top of each other,

minimizing the closed loop area and increasing the ability of the application to reject

Figure 4.

VN808 reference design board

AN2208 数据表(PDF) 9 Page - STMicroelectronics