__________Applications Information

Power-Supply Considerations

Overview

The MAX4051/MAX4052/MAX4053 and MAX4051A/

MAX4052A/MAX4053A construction is typical of most

CMOS analog switches. They have three supply pins:

V+, V-, and GND. V+ and V- are used to drive the inter-

nal CMOS switches and set the limits of the analog volt-

age on any switch. Reverse ESD-protection diodes are

internally connected between each analog signal pin

and both V+ and V-. If any analog signal exceeds V+ or

V-, one of these diodes will conduct. During normal

operation, these (and other) reverse-biased ESD diodes

leak, forming the only current drawn from V+ or V-.

Virtually all the analog leakage current comes from the

ESD diodes. Although the ESD diodes on a given signal

pin are identical, and therefore fairly well balanced,

they are reverse biased differently. Each is biased by

either V+ or V- and the analog signal. This means their

leakages will vary as the signal varies. The

difference in

the two diode leakages to the V+ and V- pins consti-

tutes the analog signal path leakage current. All analog

leakage current flows between each pin and one of the

supply terminals, not to the other switch terminal. This is

why both sides of a given switch can show leakage cur-

rents of either the same or opposite polarity.

There is no connection between the analog signal

paths and GND.

Low-Voltage, CMOS Analog

Multiplexers/Switches

______________________________________________________________________________________

11

X

1

Table 1. Truth Table/Switch Programming

X

X

All switches open

All switches open

All switches open

0

0

COM–NO0

COMB–NO0B,

COMC–NO0C

COMA–NCA,

COMB–NCB,

COMC–NCC

0

0

0

1

COM–NO1

COMB–NO1B,

COMC–NO1C

COMA–NOA,

COMB–NCB,

COMC–NCC

0

0

1

1

COM–NO3

COMB–NO3B,

COMC–NO3C

COMA–NOA,

COMB–NOB,

COMC–NCC

1

0

COM–NO2

COMB–NO2B,

COMC–NO2C

COMA–NCA,

COMB–NOB,

COMC–NCC

0

0

0

0

0

1

COM–NO5

COMB–NO1B,

COMC–NO1C

COMA–NOA,

COMB–NCB,

COMC–NOC

0

0

COM–NO4

COMB–NO0B,

COMC–NO0C

COMA–NCA,

COMB–NCB,

COMC–NOC

1

0

1

0

1

1

COM–NO7

COMB–NO3B,

COMC–NO3C

COMA–NOA,

COMB–NOB,

COMC–NOC

1

0

COM–NO6

COMB–NO2B,

COMC–NO2C

COMA–NCA,

COMB–NOB,

COMC–NOC

1

0

1

0

X = Don’t care

* ADDC not present on MAX4052.

Note: NO and COM pins are identical and interchangeable. Either may be considered an input or output; signals pass equally well

in either direction.

ON SWITCHES

ADDRESS BITS

ADDB

ADDA

MAX4051/

MAX4051A

MAX4052/

MAX4052A

MAX4053/

MAX4053A

ADDC*

INH