MAX4781 データシートの表示（PDF） - Maxim Integrated

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MAX4781

High-Speed, Low-Voltage, 0.7Ω CMOS Analog Switches/Multiplexers

Maxim Integrated 

High-Speed, Low-Voltage, 0.7Ω CMOS Analog

Switches/Multiplexers

Applications Information

Power-Supply Considerations

Overview

The MAX4781/MAX4782/MAX4783 construction is typical

of most CMOS analog switches. There are two supply

inputs: VCC and GND. VCC and GND drive the internal

CMOS switches and set the limits of the analog voltage

on any switch. Internal reverse ESD-protection diodes are

connected between each analog signal input and both

VCC and GND. If any analog signal exceeds VCC or

GND, one of these diodes conducts. During normal oper-

ation, these and other reverse-biased ESD diodes leak,

forming the only current drawn from VCC or GND.

Virtually all the analog leakage current comes from the

ESD diodes. Although the ESD diodes on a given sig-

nal input are identical and therefore fairly well bal-

anced, they are reverse-biased differently. Each diode

is biased by either VCC or GND and the analog signal.

Their leakages vary as the signal varies. The difference

in the two diodes’ leakages to VCC and GND consti-

tutes the analog-signal-path leakage current. All analog

leakage current flows between each input and one of

the supply terminals, not to the other switch terminal.

Both sides of a given switch can show leakage currents

of either the same or opposite polarity.

VCC and GND power the internal logic and set the input

logic limits. Logic inputs have ESD-protection diodes

to ground.

Power Supply

The MAX4781/MAX4782/MAX4783 operate from a sin-

gle supply between +1.6V and +3.6V. Switch on-resis-

tance increases as the supply voltage is lowered.

High-Frequency Performance

In 50Ω systems, signal response is reasonably flat up

to 50MHz (see the Typical Operating Characteristics).

Above 20MHz, the on-response has several minor

peaks that are highly layout dependent. In the off state,

the switch acts like a capacitor and passes higher fre-

quencies with less attenuation. At 10MHz, off-isolation

is approximately -50dB in 50Ω systems, becoming

worse (approximately 20dB per decade) as frequency

increases. Higher circuit impedance also degrades off-

isolation. Adjacent channel attenuation is approximate-

ly 3dB above that of a bare IC socket and is entirely

because of capacitive coupling.

Pin Nomenclature

The MAX4781/MAX4782/MAX4783 are pin compatible

with the industry-standard 74HC4051/74HC4052/

74HC4053 and the MAX4617/MAX4618/MAX4619. In

single-supply applications, they function identically and

have identical logic diagrams, although these parts dif-

fer electrically. The pin designations and logic dia-

grams in this data sheet conform to the original 1972

specifications published by RCA for the CD4051/

CD4052/CD4053. These designations differ from the

standard Maxim switch and mux designations found on

other Maxim data sheets such as the MAX4051/

MAX4052/MAX4053. Designers who are more comfort-

able with Maxim’s standard designations are advised

that the pin designations and logic diagrams on the

MAX4051/MAX4052/MAX4053 data sheet can be

applied to the MAX4781/MAX4782/MAX4783.

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