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

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.

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

6

_______________________________________________________________________________________

N

BLANKING TIME

CIRCUITRY

REVERSE CURRENT

DETECTOR

FORWARD CURRENT

DETECTOR

N

+2.0V

FLAG

OUT

IN

ON

GND

MAX4789/MAX4791/

MAX4793 ONLY

LOGIC

AUTO-

RETRY

MAX4789–MAX4794

UNDERVOLTAGE

LOCKOUT

Figure 1. Functional Diagram