Application information

STG4158

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Application information

Power-off and over-voltage protection

The STG4158 has two operation modes:

1.

Normal operation mode

2.

Isolation mode

In the normal operation mode, the switch functions as a normal SPDT, with the SEL pin that

selects the switch to be either ON or OFF. Either S1 or S2 is connected to common channel

D.

In the isolation mode, all the switches are OFF. S1 or S2 are isolated from common channel

D. The S1, S2, D port

s have a 1 MΩ impedence to ground.

The operation modes are made possible by special detection circuitry that detects the

voltage level at D, S1 and S2 supplies. Depending on these voltage levels, the device goes

into isolation mode or normal operation mode accordingly.

The isolation mode is a feature of the device that is useful during fault conditions that occur

in the application environment.

Table 9.

Voltage conditions

(voltage at common

port D, S1 or S2)

Voltage condition

Mode

Floating

0 – 4.5 V

All switches OFF

S1,S2 and D are isolated from each other

Isolation

0–0.5 V

0–4.5 V

All switches OFF

S1, S2, D are isolated from each other

Isolation

All switches OFF

S1,S2 and D are isolated from each other

Isolation

1.65 –

4.5 V

Either S1 or S2 is connected to D, depending on SEL

input

Normal