MAX4609 Maxim, MAX4609 Datasheet - Page 8

• Manufacturer Part Number: MAX4609
• Description: The MAX4607/MAX4608/MAX4609 dual analog switches feature low on-resistance of 2
• Manufacturer: Maxim

2.5 Ω , Dual, SPST,
CMOS Analog Switches
Proper power-supply sequencing is recommended for
all CMOS devices. Do not exceed the absolute maxi-
mum ratings, because stresses beyond the listed rat-
ings can cause permanent damage to the devices.
Always sequence V+ on first, then V-, followed by the
logic inputs, NO, or COM. If power-supply sequencing
is not possible, add two small signal diodes (D1, D2) in
series with supply pins 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
operation is unchanged, and the difference between
V+ and V- should not exceed 44V. These protection
diodes are not recommended when using a single supply.
With the N.C. pins connected to GND, the high-fre-
quency on-response of these parts extends from DC to
above 100MHz with a typical loss of -2dB. When the
switch is turned off, however, it behaves like a capaci-
tor, and off-isolation decreases with increasing frequen-
cy. (Above 300MHz, the switch actually passes more
signal turned off than turned on.) This effect is more
pronounced with higher source and load impedances.
Figure 2. Switching-Time Test Circuit
8
_______________________________________________________________________________________
SWITCH
MAX4607
MAX4608
MAX4609
INPUT
LOGIC
INPUT
V
Off-Isolation at High Frequencies
COM_
Applications Information
REPEAT TEST FOR EACH SWITCH. FOR LOAD
CONDITIONS, SEE ELECTRICAL CHARACTERISTICS.
C
V
O
L
INCLUDES FIXTURE AND STRAY CAPACITANCE.
= V
COM_
IN_
+5V
GND
COM
VL
0
(
Overvoltage Protection
R
L
R
+ R
L
ON
)
OR NC_
+15V
-15V
V+
V-
NO_
R
100Ω
L
SWITCH
OUTPUT
C
35pF
L
V
O
Above 5MHz, circuit-board layout becomes critical, and
it becomes difficult to characterize the response of the
switch independent of the circuit. The graphs shown in
the Typical Operating Characteristics were taken using
a 50Ω source and load connected with BNC connectors
to a circuit board deemed “average;” that is, designed
with isolation in mind, but not using strip-line or other
special RF circuit techniques. For critical applications
above 5MHz, use the MAX440, MAX441, and MAX442,
which are fully characterized up to 160MHz.
Figure 1. Overvoltage Protection Using External Blocking
Diodes
OUTPUT
SWITCH
LOGIC
INPUT
COM_
Test Circuits/Timing Diagrams
+3V
0V
0V
LOGIC INPUT WAVEFORMS INVERTED FOR SWITCHES
THAT HAVE THE OPPOSITE LOGIC SENSE.
t
*
V
ON
*
50%
O
V+
V-
-15V
+15V
0.9V
D1
D2
0
* INTERNAL PROTECTION DIODES
*
*
t
OFF
t r < 20ns
t f < 20ns
0.9V
MAX4607
MAX4608
MAX4609
NO_
0