MAX4555CSE データシートの表示（PDF） - Maxim Integrated

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MAX4555CSE

Force-Sense Switches

Maxim Integrated 

Force-Sense Switches

Figure 6 shows how to switch a single voltage or cur-

rent source between two loads using the MAX4554 or

MAX4556. By interchanging loads and sources, the cir-

cuits can be reversed so that they switch two sources

to a single load. The two loads are electrically connect-

ed together at one point, but may be physically sepa-

rated. This means that one force wire does not need to

be switched, but the corresponding sense wires do.

The MAX4554 has independent 3PST, NO switches dri-

ven out of phase by an external CMOS inverter, so that

one switch is on while the other is off. If both switches

were turned on at the same time, both loads would be

connected, and the resulting voltage at either load

would be close to (but not exactly equal to) the desired

value; this would not cause any damage to the device.

Switching 3-Wire Guarded Circuits

Figure 7 shows how to switch a single guarded voltage

or current source between two loads using the

MAX4554 or MAX4556. By interchanging loads and

sources, the circuits can be reversed to switch two

sources to a single load. If the loads have a common

connection, the switch to that node can be eliminated.

Note that these circuits use sense (high-resistance)

switches to switch the common wire. This is permissible

only if the load currents are very low. If the currents are

high, the common connection should not be switched

unless another force switch is substituted.

FEEDBACK

V

VOLTAGE/CURRENT SOURCE

FORCE

SENSE

SENSE

FORCE

LOGIC

IN

LOAD

0

1

1

2

FEEDBACK

V

FORCE

SENSE

SENSE

VOLTAGE/CURRENT SOURCE

FORCE

LOGIC

IN

LOAD

0

1

1

2

V+

V-

VL

MAX4556

NC1

COM1

NO1

NC2

COM2

NO2

NC3

COM3

NO3

IN1

IN2

GND

IN

IN3

V+

V-

VL

FCOM

SCOM

GCOM

IN1

IN2

IN

MAX4554

NOF1

NOF2

NOS1

NOS2

NOG2

NOG1

GND

EN

CMOS INVERTER

LOAD2

LOAD1

LOAD2

LOAD1

Figure 6. Using the MAX4554/MAX4556 to Switch 4-Wire Force-Sense Circuits from One Source to Two Loads

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