Reverse-Current Protection

is shut off and FLAG is asserted if the reverse current-limit

condition persists for more than the blanking time. This

feature prevents excessive reverse currents from flowing

through the device.

Switch-On/Off Control

Toggle ON high to enable the current-limited switches.

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 MAX4772/MAX4773 current-limit

switches.

FLAG Indicator

The MAX4772/MAX4773 feature a fault output (FLAG).

Whenever an overcurrent condition is encountered, the

MAX4772 latches FLAG low and turns the switch off.

The MAX4773 latches FLAG low and keeps it low until

the overcurrent conditon is removed. During this time,

the switch cycles on and off in the autoretry mode.

When the overcurrent condition is removed, FLAG

deasserts and the switch turns on (Figure 4).

FLAG is an open-drain output transistor and requires an

external pullup resistor from FLAG to IN. During shut-

down (ON is low), the pulldown on FLAG output is

released in order to limit power dissipation. FLAG goes

low when any of the following conditions occur:

• The die temperature exceeds the thermal-shutdown

temperature limit of +150°C.

• The device is in current limit for more than the fault-

blanking period.

• The switch is in autoretry.

Autoretry (MAX4773)

When the forward or reverse current-limit threshold is

The timer resets if the overcurrent condition disappears

during that time, the switch is latched off and FLAG

again. If the fault still exists, the cycle is repeated. If the

fault has been removed, the switch stays on and FLAG

deasserts.

200mA/500mA Selectable

Current-Limit Switches

_______________________________________________________________________________________

7

ON

FAULT

SWITCH ON/OFF

SUPPLY CURRENT MODE

Low

X

OFF

Shutdown

High

Thermal

Latch off

Latch off

High

Current Limit

MAX4773 cycle repeats until fault is removed

See the Autoretry section

Table 1. MAX4772/MAX4773 Switch Truth Table

after Power-Up)

100

µA (MAX)

200mA

500mA

Simultaneously)

500mA