 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
The autoretry feature saves system power in the case of 
an  overcurrent  or  short-circuit  condition.  During  tBLANK, 
when the switch is on, the supply current is at the current 
limit. During tRETRY, when the switch is off, the current 
through the switch is zero. Instead of observing the full load  
current, the switch sees the equivalent load current 
times duty cycle or ISUPPLY = ILOAD x tBLANK/(tBLANK + 
tRETRY). With a typical tBLANK = 37ms and typical tRETRY = 
555ms, the duty cycle is 6%, which results in a 94% power 
savings over the switch being on the entire time. The duty 
cycle is consistent across the process and devices.
Latchoff 
(MAX4914B/MAX4915B/MAX4917B)
When  the  forward  or  reverse  current-limit  threshold  is 
exceeded, the tBLANK timer begins counting. The timer 
resets if the overcurrent condition disappears before 
tBLANK has elapsed. The switch is shut off if the overcurrent 
condition continues up to the end of the blanking time. 
Reset the switch by either toggling ON (Figure  3a) or 
cycling the input voltage below UVLO, typically 2V (Figure 3b).
Fault Blanking
All devices feature 14ms (min) fault blanking. 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, 
FLAG asserts low. Load-transient faults less than tBLANK 
do not cause a FLAG output assertion. Only current-limit 
faults are blanked.
A thermal fault and input voltage drops below the UVLO 
threshold cause FLAG to assert immediately and not wait 
for the blanking time.
Thermal Shutdown
The devices have a thermal-shutdown feature to protect 
the devices from overheating. The switch turns off and 
FLAG goes low immediately (no fault blanking) when the 
junction temperature exceeds  +150°C. The switch  turns 
back on when the device temperature drops approximately 
by 15°C.
Applications Information
Input Capacitor
To  limit the input-voltage drop during momentary output 
short-circuit  conditions,  connect  a  capacitor  from  IN  to 
GND.  A  0.1μF  ceramic  capacitor  is  adequate  for  most 
applications; however, higher capacitor values further 
reduce the voltage drop at the input and are recommended 
for lower voltage applications.
Output Capacitance
Connect a 0.1μF capacitor from OUT to GND. This capacitor 
helps prevent inductive parasitics from pulling OUT  
negative  during  turn-off, thus  preventing  the  devices  from 
tripping erroneously. If the load capacitance is too large, 
the current may not have enough time to charge the  
capacitance and the device assumes that there is a faulty 
load condition. The maximum capacitive load value that can 
be driven from OUT is obtained by the following formula:
FWD_MIN BLANK_MIN
MAX
CV
<
Figure 3. MAX4914B/MAX4915B/MAX4917B Latchoff Fault 
Blanking
LOAD
CURRENT
SWITCH
STATUS
ON PIN
VOLTAGE
tBLANK tBLANK
OFF
ON
UVLO
LOAD
CURRENT
SWITCH
STATUS
IN PIN
VOLTAGE
OFF
ON
tBLANK tBLANK
FLAG PIN
STATUS
FLAG PIN
STATUS
FIGURE 3a
FIGURE 3b
MAX4914B/MAX4915A/B/
MAX4917A/B
100mA/200mA/300mA Current-Limit Switches
with Low Shutdown Reverse Current
www.maximintegrated.com Maxim Integrated  
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