MAX4789–MAX4794
Detailed Description
The MAX4789–MAX4794 are forward/reverse current-
limited switches that operate from a 2.3V to 5.5V input
voltage range and guarantee a 200mA, 250mA, and
300mA minimum current-limit threshold for different
options. The voltage drop across an internal sense
resistor is compared to two reference voltages to indi-
cate a forward or reverse current-limit fault. When the
load current exceeds the preset current limit for greater
than the fault-blanking time, the switch opens.
The MAX4790, MAX4792, and MAX4794 have an
autoretry function that turns on the switch again after an
internal retry time expires. If the faulty load condition is
still present after the blanking time, the switch turns off
again and the cycle is repeated. If the faulty load condi-
tion is not present, the switch remains on.
The MAX4789, MAX4791, and MAX4793 do not have
the autoretry option and the switch remains in latch-off
mode until the ON pin or the input power is cycled from
high to low and then high again.
The undervoltage lockout (UVLO) circuit prevents erro-
neous switch operation when the input voltage goes too
low during startup conditions.
Reverse Current Protection
The MAX4789–MAX4794 limit the reverse current (V
OUT
to V
IN
) from exceeding the maximum I
REV
value. The
switch is shut off and FLAG is asserted (MAX4789/
MAX4791/MAX4793) if the reverse current-limit condition
persists for more than the blanking time. This feature pre-
vents excessive reverse currents from flowing through the
device.
Switch-On/Off Control
Toggle ON high to enable the current-limited switches.
The switches are continuously on, only if V
IN
exceeds the
UVLO threshold (typically 2V) and there is no fault. When
a forward/reverse current fault is present or the die
exceeds the thermal-shutdown temperature of +150°C,
OUT is internally disconnected from IN and the supply
current decreases to 8µA (latch off). The switch is now
operating in one of its off states. The switch-off state also
occurs when driving ON low, thus reducing the supply
current (shutdown) to 0.01µA. Table 1 illustrates the
ON/OFF state of the MAX4789–MAX4794 current-limit
switches.
FLAG
Indicator
The MAX4789, MAX4791, and MAX4793 feature a
latched fault output, FLAG. Whenever a fault is activat-
ed, it latches FLAG output low and also turns the switch
200mA/250mA/300mA Current-Limit Switches
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