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, NC, 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 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.
Off-Isolation at High Frequencies
In 50Ω systems, the high-frequency on-response of
these parts extends from DC to above 300MHz, with a
typical loss of -2dB. When the switch is turned off, how-
ever, it behaves like a capacitor, and off-isolation
decreases with increasing frequency. This effect is
more pronounced with higher source and load imped-
ances. Above 5MHz, circuit board layout becomes criti-
cal. The graphs shown in the Typical Operating
Characteristics were taken using a 50Ω source and
load connected with BNC connectors.
MAX4647/MAX4648
25Ω SPST Analog Switches in SOT23-6
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