MAX328 Просмотр технического описания (PDF) - Maxim Integrated
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MAX328 Datasheet PDF : 10 Pages
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Ultra-Low Leakage Monolithic CMOS
Analog Multiplexers
Applications Information
Figure 4 is a typical circuit for converting the
MAX328/MAX329 into a fault-tolerant mux. In this
application, the internal diodes limit the voltage at the
MAX328 input to ±15.7V (±15V supplies). No external
diodes need to be added with the MAX328/MAX329,
unlike conventional multiplexers requiring external
diodes.
The resistors, R, need to be 39kΩ or higher to limit the
power dissipation in the resistor when a 120V AC fault
occurs (i.e., power dissipation is (120-16)2/39kΩ or
0.28W. This is why a 1/2/W resistor is needed). The circuit
withstands an indefinite fault to a 120V AC line with no
damage to any component.
In addition to allowing fault-protection, the guaranteed
low leakage of the MAX328/MAX329 also reduces signal
errors. The circuit in Figure 4 produces an error voltage of
10pA (max leakage) x 39kΩ or 0.39µV at room tempera-
ture and 39µV at +125°C. Therefore, for 10V signals, the
MAX328/MAX329 allows 17-bit resolution (38µV = 1LSB)
over the full temperature range.
A0 1
EN 2
-15V
3
1µF
R
S1
4
R
S2
5
R
S3
6
R
S4
7
D8
R = 39kΩ 1/2W
MAX328
16 A1
15 A2
14
13
+15V
1µF
R
12
S5
R
11
S6
R
10
S7
R
9
S8
Figure 4. Fault-Tolerant Mux (indefinitely withstands 120V AC
fault voltages)
TOP VIEW
Functional Diagrams
V- 1
S1 2
S2 3
S3 4
LOGIC
12 GND
11 V+
10 S5
9 S6
V- 1
S1A 2
S2A 3
S3A 4
LOGIC
12 V+
11 S1B
10 S2B
9 S3B
MAX328
MAX329
8 _______________________________________________________________________________________
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