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AS1747, AS1748, AS1749, AS1750

Datasheet - D e t a i l e d D e s c r i p t i o n

8 Detailed Description

The AS1747– AS1750 are operating from a +1.8V to +5.5V supply and feature a negative signal capability that allows

signals below ground to pass through without distortion. A break-before-make switching and a low on-resistance are

also included in this analog dual SPDT switches. The device is fully specified for a 3.0V application.

A headphone or mute detection is included in the AS1748 and AS1750. This function is realized with a comparator

between precharged points the AS1749 and AS1750 have an internal shunt switch. This shunt switch automatically

discharges any capacitance at the NO and NC connection points.

9 Application Information

Digital Control Inputs

The logic inputs of the AS1747– AS1750 accept up to +5.5V independent of the supply voltage. Due to this a mixing of

the logic levels in a system is possible. For example, with a +3.3V supply, IN_ can be driven low to GND and high to

+5.5V. For a +1.8V supply voltage, the logic levels are 0.5V (low) and 1.4V (high); for a +5V supply voltage, the logic

levels are 0.8V (low) and 2.0V (high).

Analog Signal Levels

The change of the on-resistance of the AS1747– AS1750 is very little for analog input signals over the whole supply

voltage range. The switches are bi-directional, so the NO_, NC_, and COM_ pins can be either inputs or outputs.

Comparator (AS1748

1

/AS1750)

To implement a mute and headphone function, a comparator is included in the AS1748 and AS1750. The negative ter-

The output of the comparator (CMPO) is logic high when the negative terminal (CMP-) is below the threshold. CMPO is

phone detection.

Shunt Switch (AS1749

1

/AS1750)

Due to the switching between audio sources, audible click-and-pop sounds occur. To reduce this sounds a 100

Ω shunt

switch is implemented in the AS1749 and AS1750. This shunt switch automatically discharges any capacitance at the

NC_ or NO_ terminals when they are unconnected to COM_.

Audible clicks and pops are caused when a step DC voltage is switched into the speaker. By automatically discharging

the side that is not connected, any residual DC voltage is removed, thereby reducing the clicks and pops.

Power-Supply Sequencing and Overvoltage Protection

Caution:

Stresses beyond the listed absolute maximum ratings in Table 3 on page 4 may cause permanent damage

to the device. Exposure to absolute maximum rating conditions for extended periods may affect device

reliability.

signals, especially if the analog signal is not current-limited.

1. on request