Datasheet
MAX4677/MAX4678/MAX4679
2Ω, Quad, SPST, CMOS Analog Switches
8 _______________________________________________________________________________________
___________Applications Information
Overvoltage Protection
Proper power-supply sequencing is recommended for
all CMOS devices. Do not exceed the absolute maxi-
mum ratings because stresses beyond the listed ratings
can cause permanent damage to the devices. Always
sequence V+ on first, then V-, then V
L
followed by the
logic inputs, NO_, NC_, or COM. If proper power-supply
sequencing is not possible, add two small signal diodes
(D1, D2) in series with the supply pins, and a Schottky
diode between V+ and V
L
for overvoltage protection
(Figure 1). Adding diodes reduces the analog signal
range to one diode drop below V+ and one diode drop
above V-, but does not affect the devices’ low switch
resistance and low leakage characteristics. Device oper-
ation is unchanged, and the difference between V+ and
V- should not exceed 11V.
Power-supply bypassing improves noise margin and
prevents switching noise from propagating from the V+
supply to other components. A 0.1µF capacitor connect-
ed from V+ to GND is adequate for most applications.
Figure 1. Overvoltage Protection Using External Blocking Diodes
COM_
V
2
V-
V+
NO_
V
L
D1
D2
*
*
*
*
*INTERNAL PROTECTION DIODES
MAX4677
MAX4678
MAX4679
t
r
< 20ns
t
f
< 20ns
50%
0
LOGIC
INPUT
V-
V-
R
L
300Ω
NO_
OR NC_
GND
C
L
INCLUDES FIXTURE AND STRAY CAPACITANCE.
V
OUT
= V
COM (
R
L
)
R
L
+ R
ON
SWITCH
INPUT
IN_
+3V
t
OFF
0
COM_
SWITCH
OUTPUT
0.9 x V
0UT
0.9 x V
OUT
t
ON
V
OUT
SWITCH
OUTPUT
LOGIC
INPUT
C
L
35pF
V+
V+
V+
V
L
V
OUT
V
COM
0V
MAX4677
MAX4678
MAX4679
Figure 2. Switching Time
50%
0.9 x V
0UT1
+3V
0
0
LOGIC
INPUT
SWITCH
OUTPUT 2
(V
OUT2
)
0
0.9 x V
OUT2
t
D
t
D
LOGIC
INPUT
V-
V-
R
L2
GND
C
L
INCLUDES FIXTURE AND STRAY CAPACITANCE.
COM2
I
N1
COM1
V
OUT2
V+
V+
C
L2
V
COM1
= +3V
R
L1
V
OUT1
C
L1
R
L
= 300Ω
C
L
= 35pF
NO1
NC2
SWITCH
OUTPUT 1
(V
OUT1
)
MAX4679
V
COM2
= +3V
V+
V
L
I
N2
Figure 3. Break-Before-Make Interval (MAX4679 Only)