MAX4772/MAX4773
Detailed Description
The MAX4772/MAX4773 are forward/reverse current-
limited switches that operate from a 2.0V to 4.5V input
voltage range and guarantee a 200mA or 500mA mini-
mum current-limit threshold when driving SEL low or
high, respectively. The voltage drop across an internal
sense resistor is compared to two reference voltages to
indicate 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 MAX4773 has 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 blank-
ing time, the switch turns off again and the cycle is
repeated. If the faulty load condition is not present, the
switch remains on.
The MAX4772 does 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.
Current-Limit Threshold Selection
The MAX4772/MAX4773 SEL logic input sets the
desired minimum current-limit threshold to 200mA or
500mA. Connect SEL low or leave floating for 200mA
current limit and high for the 500mA current limit.
During power-up, if SEL is low or floating, the current limit
is set to 200mA. The MAX4772/MAX4773 uses an internal
pulldown resistor (100µA, max) to set the default current
limit to 200mA when SEL is floating. After the first low-to-
high transition, the pulldown resistor is internally discon-
nected and the level on SEL determines the current limit
(SEL = low, 200mA and SEL = high, 500mA).
During power-up, if SEL and V
IN
rise together, the cur-
rent limit is immediately set to 500mA.
Figures 2 and 3 illustrate the two different modes of
power-up sequence for the MAX4772/MAX4773. In
Figure 2, the switch powers up, V
IN
≥ 2V, a low-to-high
transition on SEL changes the current limit from 200mA to
500mA. In Figure 3, the switch powers up in the 500mA
current-limit mode with SEL and IN rising simultaneously.
The microprocessor’s GPIO must be able to source the
100µA drive current for the MAX4772/MAX4773 500mA
current-limit operation. After the current limit has been set
to 500mA, the 100µA driving current is no longer needed.
200mA/500mA Selectable
Current-Limit Switches
6 _______________________________________________________________________________________
Figure 1. Functional Diagram
