Datasheet

MAX4554/MAX4555/MAX4556
Force-Sense Switches
20 ______________________________________________________________________________________
Increasing V- has no effect on the logic-level thresh-
olds, but it does increase the drive to the internal P-
channel switches, reducing the overall switch
on-resistance. V- also sets the negative limit of the ana-
log signal voltage.
Bipolar-Supply Operation
The MAX4554/MAX4555/MAX4556 operate with bipolar
supplies between ±4.5V and ±18V. However, since all
factory characterization is done with ±15V supplies
(and +20V, -10V for MAX4554), operation at other sup-
plies is not guaranteed. The V+ and V- supplies need
not be symmetrical, but their sum cannot exceed the
absolute maximum rating of 44V (see Absolute Max-
imum Ratings ). VL must not exceed V+.
Single-Supply Operation
The MAX4554/MAX4555/MAX4556 operate from a sin-
gle supply between +4.5V and +44V when V- is con-
nected to GND. All of the bipolar precautions must be
observed.
__________Applications Information
Switching 4-Wire
Force-Sense Circuits
Figure 5 shows how to switch a single voltage or cur-
rent source between two loads using two MAX4555s. A
single CMOS inverter ensures that only one switch is on
at a time. On each MAX4555, switches 2 and 3 are the
high-current switches, so they should be used for force
circuits. By interchanging loads and sources, the circuit
can be reversed to switch two sources to a single load.
Additional MAX4555s and loads or sources can be
added to expand the circuit, but additional IN_ address
decoding must be incorporated.
NC3
GND
GND
LOAD1
LOAD2
NC1
FEEDBACK
SENSE
SENSE
FORCE
CMOS INVERTER
IN
FORCE
COM2
V-
COM1
COM4
COM3
IN2
IN1
IN4
IN3
VOLTAGE/CURRENT SOURCE
NC2
NC4
MAX4555
V+
VL
NC3
NC1
COM2
V-
COM1
COM4
COM3
IN2
IN1
IN4
IN3
NC2
NC4
MAX4555
V+
VL
LOGIC
LOAD
2
1
0
1
IN
V
Figure 5. Using the MAX4555 to Switch 4-Wire Force-Sense Circuits from One Source to Two Loads