MAX14571 Datasheet, PDF (11/14 Pages) Maxim Integrated Products – Adjustable Overvoltage and Overcurrent Protectors with High Accuracy

MAX14571/MAX14572/MAX14573
Adjustable Overvoltage and Overcurrent
Protectors with High Accuracy
Thermal-Shutdown Protection
The MAX14571/MAX14572/MAX14753 have a thermal-
shutdown feature to protect the device from overheating.
The device turns off and the FLAG asserts when the junc-
tion temperature exceeds +150NC (typ). The devices exit
thermal shutdown and resume normal operation after the
junction temperature cools by 30NC (typ), except for the
MAX14572 which remains latched off.
The thermal limit behaves similarly to the current limit. For
the MAX14571 (autoretry), the thermal limit works with the
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.
Overvoltage Lockout (OVLO)
The devices have a 33V (typ) preset OVLO threshold
when the voltage at OVLO is set below the external
OVLO select voltage (VOVLOSEL). Connect OVLO to
GND to activate the preset OVLO threshold. Connect
the external resistors to the OVLO pin as shown in the
Typical Operating Circuit to externally adjust the OVLO
threshold. Use the following equation to adjust the OVLO
threshold. The recommended value for R3 is 2.2MI:
V_OVLO=
V_BG
×
₁
+
R3
R4^
Undervoltage Lockout (UVLO)
The devices have a 19.2V (typ) preset UVLO threshold
when the voltage at UVLO is set below the external
OVLO select voltage (VUVLOSEL). Connect UVLO to
GND to activate the preset UVLO threshold. Connect
the external resistors to the UVLO pin as shown in the
Typical Operating Circuit to externally adjust the UVLO
threshold. Use the following equation to adjust the UVLO
threshold. The recommended value for R1 is 2.2MI:
V_UVLO=
V_BG
×
₁₊
R1
R2^
Switch Control
There are two independent enable inputs (HVEN and
EN) for the devices. HVEN is a high-voltage-capable
input. Toggle HVEN or EN to reset the fault condition
once a short circuit is detected and the devices shut
down (Table 1).
Input Debounce Protection
The ICs feature input debounce protection. When the
input voltage is higher than the UVLO threshold voltage
for a period greater than the debounce time (tDEB), the
internal FETs are turned on. This feature is intended for
applications where the EN or HVEN signal is present
when the power supply ramps up (Figure 4).
Applications Information
Setting the Current Limit/Threshold
A resistor from SETI to ground programs the current limit/
threshold value for the devices. Leaving SETI uncon-
nected selects a 0A current limit/threshold. Connecting
SETI to ground asserts FLAG. Use the following formula
to calculate the current limit:
R
SETI^(kΩ)
= ¹¹⁵⁰⁰
I_LIM(mA)
IN Bypass Capacitor
Connect a minimum of 1FF capacitor from IN to GND
to limit the input voltage drop during momentary output
short-circuit conditions. Larger capacitor values further
reduce the voltage undershoot at the input.
Hot-Plug IN
In many system powering applications, an input filter-
ing capacitor is required to lower the radiated emission,
enhance the ESD capability, etc. In hot-plug applica-
tions, parasitic cable inductance, along with the input
capacitor, cause overshoot and ringing when the pow-
ered cable is connected to the input terminal.
This effect causes the protection device to see almost
twice the applied voltage. An input voltage of 24V can
easily exceed the absolute maximum rating of 40V, which
may permanently damage the device. A transient voltage
suppressor (TVS) is often used for industrial applications
to protect the system from these conditions. We recom-
mend using a TVS that is capable of limiting surge to 40V
placed close to the input terminal.
Table 1. Switch Control
HVEN
EN
0
0
1
0
0
1
1
1
SWITCH STATUS
On
Off
On
On
Maxim Integrated
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