off. 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.

Autoretry (MAX4790/MAX4792/MAX4794)

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. At the end of

exists, the cycle is repeated. If the fault has been

removed, the switch stays on.

The autoretry feature saves system power in the case

of an overcurrent or short-circuit condition. During

the current through the switch is zero. Instead of

observing the full load current, the switch sees the

cycle is 12%, which results in an 88% power savings

over the switch being on the entire time. The duty cycle

is consistent across the process and devices.

Latch Off (MAX4789/MAX4791/MAX4793)

When the forward or reverse current-limit threshold is

resets if the overcurrent condition disappears before

current condition continues up to the end of the blank-

ing time. Reset the switch by either toggling ON (Figure

3a) or cycling the input voltage below UVLO, typically

2V (Figure 3b).

Fault Blanking

The MAX4789–MAX4794 feature 14ms (min) fault blank-

ing. Fault blanking allows current-limit faults, including

momentary short-circuit faults that occur when hot

swapping a capacitive load, and also ensures that no

fault is issued during power-up. When a load transient

causes the device to enter current limit, an internal

counter starts. If the load-transient fault persists beyond

the fault-blanking timeout, the MAX4789/MAX4791/

MAX4793 FLAG asserts low. Load-transient faults less

current-limit faults are blanked.

A thermal fault and input voltage drops below the

UVLO threshold cause FLAG to assert immediately and

do not wait for the blanking time.

Thermal Shutdown

The MAX4789–MAX4794 have a thermal shutdown fea-

ture to protect the devices from overheating. The switch

turns off and FLAG goes low immediately (no fault blank-

ing) when the junction temperature exceeds +150°C.

The switch turns back on when the device temperature

drops approximately 15°C.

200mA/250mA/300mA Current-Limit Switches

_______________________________________________________________________________________

7

ON

FAULT

SWITCH ON/OFF

SUPPLY CURRENT MODE

Low

X

OFF

Shutdown

High

Undervoltage Lockout

OFF

Shutdown

High

Thermal

Latch off

Latch off

High

Current Limit

MAX4790, MAX4792, and MAX4794; cycle repeats until fault

is removed

See the Autoretry section

Table 1. MAX4789–MAX4794 Switch Truth Table

LOAD

CURRENT

SWITCH

STATUS

OFF

ON

CURRENT

LIMIT

SHORT

CONDITION

REMOVED

Figure 2. MAX4790/MAX4792/MAX4794 Autoretry Fault

Blanking Diagram