__________Applications Information

Power-Supply Considerations

The MAX4524/MAX4525’s construction is typical of

most CMOS analog switches. They have two supply

pins: V+ and GND. V+ and GND are used to drive the

internal CMOS switches and set the limits of the analog

voltage on any switch. Reverse ESD-protection diodes

are internally connected between each analog signal

pin and both V+ and GND. If any analog signal

exceeds V+ or GND, 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 GND.

Virtually all the analog leakage current comes from the

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

nal pin are identical, and therefore fairly well balanced,

they are reverse-biased differently. Each is biased by

either V+ or GND and the analog signal. This means

that leakage will vary as the signal varies. The differ-

ence in the two diode leakages to the V+ and GND

pins constitutes 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 ter-

minal. This is why both sides of a given switch can

show leakage currents of either the same or opposite

polarity.

Low-Voltage, Single-Supply

Multiplexer and Switch

_______________________________________________________________________________________

7

______________________________________________Test Circuits/Timing Diagrams

50%

V+

0V

0V

90%

90%

50%

V+

0V

0V

90%

90%

V+

GND

V+

ADDB

ADDA

INH

NO0

NO1–NO2

NO3

COM

V+

MAX4524

300

Ω

50

Ω

35pF

V+

GND

V+

ADD

INH

NO

NC

COM

V+

MAX4525

300

Ω

50

Ω

35pF

REPEAT TEST FOR EACH SECTION.

Figure 1. Address Transition Time