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Revision 1.41

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AS1751/AS1752/AS1753

9 Application Information

Power Supply Sequencing

Proper power-supply sequencing is critical for proper switch operation. The power supplies should be started up in the

following sequence:

1. V+

2. NOx, NCx, COMx

Note:

Do not exceed the absolute maximum ratings (see page 2).

Overvoltage Protection

ON-resistance increases slightly at lower supply voltages.

Figure 12. Overvoltage Protection using 2 External Blocking Diodes

Adding diode D2 to the circuit shown in Figure 12 causes the logic threshold to be shifted relative to GND. Diodes D1

and D2 also protect against overvoltage conditions.

For example, in the circuit shown in Figure 12, if the supply voltage goes below the absolute maximum rating, and if a

fault voltage up to the absolute maximum rating is applied to an analog signal pin, no damage will result.

Power Supply Bypass

Power supply connections to the devices must maintain a low impedance to ground. This can be done using a bypass

capacitor, which will also improve noise margin and prevent switching noise propagation from the V+ supply to other

components.

A 0.1µF bypass capacitor, connected from V+ to GND (see Figure 18 on page 11), is adequate for most applications.

Logic Inputs

Driving INx Rail-to-Rail will help minimize power consumption.

Layout Considerations

High-speed switches require proper layout and design procedures for optimum performance.

!

Short, wide traces should be used to reduce stray inductance and capacitance.

!

Bypass capacitors should be as close to the device as possible.

!

Large ground planes should be used wherever possible.

AS1751/AS1752/AS1753

GND

COMx

D2

D1

V+

V+

NOx