MAX4626/MAX4627/MAX4628
0.5Ω, Low-Voltage, Single-Supply
SPST Analog Switches
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Detailed Description
The MAX4626/MAX4627/MAX4628 are low-on-resis-
tance (R
ON
), low-voltage, single-pole/single-throw
(SPST) analog switches that operate from a +1.8V to
+5.5V single supply. The MAX4626 is normally open
(NO), and the MAX4627 is normally closed (NC). The
MAX4628 is normally open (NO) and has two control
inputs.
When powered from a +5V supply, their 0.5Ω R
ON
allows high continuous currents to be switched in a
variety of applications. In the event of an overcurrent
condition, these switches provide both current-limit and
thermal-shutdown protection.
Current-Limit Protection
The MAX4626/MAX4627/MAX4628 feature current-limit
protection circuitry. When the voltage drop across the
on switch reaches 0.6V (typ), the internal circuitry acti-
vates. The current limit is not instantaneous, but rather
integrates over time so that current limiting will not acti-
vate under momentary short-circuit conditions encoun-
tered when the switch output charges a small 0.1µF
capacitor. For sustained overcurrent conditions, the
switch turns off (opens). The switch turns on after 5ms
and, if the overload condition persists, the switch will
cycle off and on to produce a pulsed output. A direct
short circuit will be detected immediately, and the
switch will pulse on for 1µs, then remain off for 5ms.
Applications Information
Logic Inputs
The MAX4626/MAX4627/MAX4628 logic inputs can be
driven up to +5.5V regardless of the supply voltage. For
example, with a +3.3V supply, IN or IN may be driven
low to 0V and high to 5.5V. Driving IN or IN Rail-to-Rail
®
minimizes power consumption.
Analog Signal Levels
Analog signals that range over the entire supply voltage
(V+ to GND) can be passed with very little change in
on-resistance (see Typical Operating Characteristics).
The switches are bidirectional, so the NO, NC, and
COM pins can be used as either inputs or outputs.
Power-Supply Sequencing and
Overvoltage Protection
Caution: Do not exceed the absolute maximum rat-
ings; stresses beyond the listed ratings may cause
permanent damage to the devices.
Proper power-supply sequencing is recommended for
all CMOS devices. Always apply V+ before applying
analog signals, especially if the analog signal is not
current limited. If this sequencing is not possible, and if
the analog inputs are not current limited to <20mA, add
a small-signal diode (D1) as shown in Figure 1. If the
analog signal can dip below GND, add D2. Adding
protection diodes reduces the analog range to a diode
drop (about 0.7V) below V+ (for D1), and a diode drop
above ground (for D2). On-resistance increases by a
small amount at low supply voltages. Maximum supply
voltage (V+) must not exceed +6V.
Adding protection diode D2 causes the logic thresh-
olds to be shifted relative to GND. TTL compatibility is
not guaranteed when protection diode D2 is added.
Protection diodes D1 and D2 also protect against some
overvoltage situations. With Figure 1’s circuit, if the sup-
ply voltage is below the absolute maximum rating, and
if a fault voltage up to the absolute maximum rating is
applied to an analog signal pin, no damage will result.
