MAX4667/MAX4668/MAX4669
2.5
Ω
, Dual, 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 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 (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 leak-
age characteristics. Device operation is unchanged,
and the difference between V+ and V- should not
exceed 44V. These protection diodes are not recom-
mended when using a single supply.
Off-Isolation at High Frequencies
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.
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 stripline 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
Pin Description
13 13 Positive Analog Supply Voltage InputV+13
12 12 Logic Supply InputV
L
12
14, 11 14, 11 Analog Switch, Common TerminalsCOM1, COM214, 11
5 5 GroundGND5
2, 7 2, 7 Logic-Control Digital InputsIN2, IN22, 7
— — Analog Switch, Normally Closed Terminal
1, 3, 6, 8,
10, 15
1, 3, 6, 8,
10, 15
No Connection. Not internally connected. Connect to GND as
low impedance to improve on/off-isolation.
— — Analog Switch, Normally Open TerminalNO116
NC19
16, 9 — Analog Switch, Normally Closed Terminals
— 16, 9 Analog Switch, Normally Open TerminalsNO1, NO2—
NC1, NC2—
4 4
Negative Analog Supply Voltage Input. Connect to GND for
single-supply operation.
V-4
N.C.
NAME
PIN
1, 3, 6, 8,
10, 15
MAX4669MAX4668
FUNCTION
MAX4667
