Rainbow Electronics MAX14523C - Manual (Page 8)

MAX14523A/MAX14523AL/MAX14523B/MAX14523C
250mA to 1.5A, Adjustable
Current-Limit Switches
8 _______________________________________________________________________________________
Functional Diagram
MAX14523A
MAX14523AL
MAX14523B
MAX14523C
BUFFER
IN
N.C.
THERMAL
SHUTDOWN
CONTROL
LOGIC
REVERSE-
CURRENT
PROTECTION
TIMING
CIRCUITRY
BUFFER
CURRENT
LIMIT
BANDGAP
REFERENCE
OUT
FLAG
SETI
*( ) FOR THE MAX14523AL ONLY
ON/(ON)*
GND
Detailed Description
The MAX14523A/MAX14523AL/MAX14523B/MAX14523C
programmable current-limit switches operate from
+1.7V to +5.5V and provide internal current limiting
adjustable from 250mA to 1.5A. These devices feature
a fixed blanking time, and a FLAG output that notifies
the processor when a fault condition is present.
Programmable Current Limit/Threshold
A resistor from SETI to GND sets the current
limit/threshold for the switch (see the
Setting the
Current Limit/Threshold section). If the output current is
limited at the current threshold value for a time equal to
or longer than t
BLANK , the output flag asserts and the
MAX14523A/MAX14523AL enter the autoretry mode,
the MAX14523B latches off the switch, and the
MAX14523C enters the continuous current-limit mode.
Autoretry (MAX14523A/MAX14523AL)
When the forward current reaches the current thresh-
old, the t
BLANK timer begins counting (Figure 2). FLAG
asserts if the overcurrent condition is present for
t
BLANK or longer. The timer resets if the overcurrent
condition disappears before the blanking time (t BLANK )
has elapsed. A retry time delay (t RETRY ) starts immedi-
ately after the blanking time has elapsed. During that
time, the switch latches off. At the end of t
RETRY , the
switch turns on again. If the fault still exists, the cycle
repeats. If the fault has been removed, the switch stays
on. During this cycle, FLAG stays low. In autoretry, if
the die temperature exceeds +170°C (typ) due to self
heating, the MAX14523A/MAX14523AL go into thermal
shutdown until the die temperature drops by approxi-
mately 15°C (see the
Thermal Shutdown section.)