MAX14571 Datasheet, PDF (12/14 Pages) Maxim Integrated Products – Adjustable Overvoltage and Overcurrent Protectors with High Accuracy

MAX14571/MAX14572/MAX14573
Adjustable Overvoltage and Overcurrent
Protectors with High Accuracy
OUT Bypass Capacitor
For stable operation over the full temperature range
and over the entire programmable current-limit range,
connect a 1FF ceramic capacitor from OUT to ground.
Excessive output capacitance can cause a false over-
current condition due to decreased dV/dt across the
capacitor. Calculate the maximum capacitive load
(CMAX) value that can be connected to OUT by using
the following formula:
C_MAX (µF)
=
I_LIM(mA)
x
t _BLANK(MIN)
V_IN(V)
(ms)
For example, for VIN = 24V, tBLANK = 15ms, and ILIM =
4.2A, CMAX equals 2625FF.
Output Freewheeling Diode for
Inductive Hard Short to Ground
In applications that require protection form a sudden
short to ground with an inductive load or long cable, a
Schottky diode between the OUT terminal and ground
is recommended. This is to prevent a negative spike on
OUT due to the inductive kickback during a short-circuit
event.
Thermal-Shutdown Protection
The MAX14571/MAX14572/MAX14573 have a thermal-
shutdown feature to protect the device from overheat-
ing. The device turns off and the FLAG asserts when the
junction temperature exceeds +150°C (typ). The devices
exit thermal shutdown and resume normal operation after
the junction temperature cools by 30°C (typ), except for
the MAX14572, which remains latched off.
The thermal limit behaves similar to the current limit. For
the MAX14571 (autoretry), the thermal limit works with
autoretry timer. When the device comes out of the ther-
mal limit, it starts after the retry time. For the MAX14572
(latch off), the device latches off until power or EN cycle.
For the MAX14573 (continuous), the device only disables
while the temperature is over the limit. There is no blank-
ing time for thermal protection.
Layout and Thermal Dissipation
To optimize the switch response time to output short-
circuit conditions, it is very important to keep all traces
as short as possible to reduce the effect of undesirable
parasitic inductance. Place input and output capaci-
tors as close as possible to the device (no more than
5mm). IN and OUT must be connected with wide short
traces to the power bus. During normal operation, the
power dissipation is small and the package temperature
change is minimal. If the output is continuously shorted
to ground at the maximum supply voltage, the switches
with the autoretry option do not cause thermal-shutdown
detection to trip:
P_(MAX)
=
V_IN(MAX) × I_OUT(MAX) ×
t_RETRY + t_BLANK
t _BLANK
Attention must be given to the MAX14573 continuous
current-limit version when the power dissipation dur-
ing a fault condition can cause the device to reach
the thermal-shutdown threshold. Thermal vias from the
exposed pad to ground plane are highly recommended
to increase the system thermal capacitance while reduc-
ing the thermal resistance to the ambient.
ESD Test Conditions
The devices are specified for Q15kV (HBM) typical ESD
resistance on IN when IN is bypassed to ground with a
1FF low-ESR ceramic capacitor. No capacitor is required
for Q2kV (HBM) typical ESD on IN. All the pins have a
Q2kV (HBM) typical ESD protection.
HBM ESD Protection
Figure 5a shows the Human Body Model, and Figure
5b shows the current waveform it generates when dis-
charged into a low impedance. This model consists of a
100pF capacitor charged to the ESD voltage of interest,
which is then discharged into the device through a 1.5kI
resistor.
12  
Maxim Integrated