Detailed Description

The MAX4914B/MAX4915A/B/MAX4917A/B are for-

ward/reverse current-limited switches that operate from

a +2.3V to +5.5V input voltage range and guarantee a

100mA, 200mA, and 300mA minimum current-limit

threshold for different options. 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 and

FLAG asserts.

The MAX4915A/MAX4917A 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 condition is not pre-

sent, the switch remains on. During this retry time,

FLAG remains low until the fault is removed.

The MAX4914B/MAX4915B/MAX4917B do not have the

autoretry option, and the switch remains in latchoff

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.

Reverse Current Protection

and

FLAG is asserted 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 to the source. When the device is in shutdown

1µA (max).

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 (latchoff). 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 (typ). Table 1 illustrates the

ON/OFF state.

FLAG Indicator

All devices feature a latched fault output,

FLAG.

Whenever a fault is activated, it latches the

FLAG out-

put low and also turns the switch off.

FLAG is an open-

100mA/200mA/300mA Current-Limit Switches

with Low Shutdown Reverse Current

6

_______________________________________________________________________________________

N

BLANKING TIME

CIRCUITRY

REVERSE CURRENT

DETECTOR

FORWARD CURRENT

DETECTOR

N

+2.0V

FLAG

OUT

IN

ON

GND

LOGIC

AUTO-

RETRY

MAX4914B

MAX4915A/B

MAX4917A/B

UNDERVOLTAGE

LOCKOUT

Figure 1. Functional Diagram