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).

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

≥ 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

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Figure 1. Functional Diagram

N

BLANKING TIME

CIRCUITRY

REVERSE-CURRENT DETECTOR

FORWARD-CURRENT

DETECTOR

N

FLAG

OUT

IN

ON

GND

LOGIC

SEL

MAX4772/MAX4773