Serially Controlled, Low-Voltage,

8-Channel SPST Switch

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15

age current flows to the supply terminals, not to the

other switch terminal. This is why both sides of a given

switch can show leakage currents of either the same or

opposite polarity.

There is no connection between the analog signal

paths and GND.

V+ and GND power the internal logic and logic-level

translators, and set both the input and output logic lim-

its. The logic-level translators convert the logic levels to

switched V+ and V- signals to drive the analog signal

gates. This drive signal is the only connection between

the logic supplies (and signals) and the analog sup-

plies. V+, and V- have ESD-protection diodes to GND.

The logic-level inputs and output have ESD protection

to V+ and to GND.

The logic-level thresholds are CMOS and TTL compati-

ble when V+ is +5V. As V+ is raised, the threshold

increases slightly. So when V+ reaches +12V, the

threshold is about 3.1V; slightly above the TTL guaran-

teed high-level minimum of 2.8V, but still compatible

with CMOS outputs.

Bipolar Supplies

The MAX395 operates with bipolar supplies between

±3.0V and ±8V. The V+ and V- supplies need not be

symmetrical, but their sum cannot exceed the absolute

maximum rating of 17V. Do not connect the MAX395

V+ to +3V and connect the logic-level pins to TTL

logic-level signals. This exceeds the absolute maxi-

mum ratings and can damage the part and/or exter-

nal circuits.

Single Supply

The MAX395 operates from a single supply between

+3V and +16V when V- is connected to GND. All of the

bipolar precautions must be observed.

High-Frequency Performance

In 50

Ω systems, signal response is reasonably flat up

to 50MHz (see

Typical Operating Characteristics).

Above 20MHz, the on-response has several minor

peaks that are highly layout dependent. The problem is

not turning the switch on, but turning it off. The off-state

switch acts like a capacitor and passes higher frequen-

cies with less attenuation. At 10MHz, off isolation is

about -45dB in 50

Ω systems, becoming worse (approx-

imately 20dB per decade) as frequency increases.

Higher circuit impedances also make off isolation

worse. Adjacent channel attenuation is about 3dB

above that of a bare IC socket, and is due entirely to

capacitive coupling.

X

0

1

X

X

X

X

D6

RESET

X

X

X

0

FUNCTION

X

X

1

D4

X

X

X

1

X

X

0

D5

X

0

1

1

X

0

1

X

X

X

0

1

X

D2

DATA BITS

X

X

All switches open, D7–D0 = 0

Switch 6 off and 7 on

Switch 7 off and 6 on

X

1

X

X

1

X

X

1

X

X

X

D0

X

X

X

X

X

X

X

D1

X

1

X

X

Switch 4 off and 5 on

Switch 2 off and 3 on

Switch 3 off and 2 on

Switch 5 off and 4 on

X

X

1

0

D7

X

D3

X

X

X

X

X

1

1

0

Switch 1 off and 0 on

X

Table 2. SPDT Switch Programming

X

X

X

X

X

1

0

1

Switch 0 off and 1 on

X