MAX4914B Maxim, MAX4914B Datasheet - Page 6

• Manufacturer Part Number: MAX4914B
• Description: The MAX4914B/MAX4915A/B/MAX4917A/B family of switches feature internal current limiting to prevent damage to host devices due to faulty load conditions
• Manufacturer: Maxim

100mA/200mA/300mA Current-Limit Switches
with Low Shutdown Reverse Current
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.
Figure 1. Functional Diagram
6
_______________________________________________________________________________________
ON
IN
LOGIC
AUTO-
RETRY
Detailed Description
UNDERVOLTAGE
LOCKOUT
+2.0V
REVERSE CURRENT
FORWARD CURRENT
DETECTOR
DETECTOR
All devices limit the reverse current (V
exceeding the maximum I
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
(V
1µA (max).
Toggle ON high to enable the current-limited switches.
The switches are continuously on only if V
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.
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-
ON
< V
IL
MAX4915A/B
MAX4917A/B
), the current from OUT to IN does not exceed
MAX4914B
BLANKING TIME
CIRCUITRY
Reverse Current Protection
REV
Switch-On/Off Control
GND
value. The switch is shut off
N
FLAG
OUT
FLAG Indicator
OUT
IN
to V
exceeds the
IN
) from