NIS5101 Ver la hoja de datos (PDF) - ON Semiconductor

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componentes Descripción

Fabricante

NIS5101

Inrush Limiter/Circuit Breaker

ON Semiconductor 

NIS5101

OPERATION DESCRIPTION

Turn−on

The NIS5101 monitors the input voltage by sensing the

voltage across the Input + to Input − pins. When the UVLO

voltage has been reached, the internal circuitry slowly

charges the gate of the internal SENSEFET®. There will

be a slight delay of several milliseconds before the

SENSEFET begins conduction. This may be increased by

adding a capacitor to the UVLO pin. For a discussion of

this, see application note AND8115/D.

The SENSEFET will increase the load current with a

controlled di/dt until the current limit level has been

reached. At this point the SENSEFET will enter a constant

current mode of operation until the load capacitor has been

fully charged. If the thermal limit threshold is reached

before the capacitor reaches its final charge level, the

device will shut down until the die temperature reaches

95°C and then restart, if it is the auto−retry device. The

thermal latching version must not be allowed to reach the

thermal shutdown level at turn−on as this will cause it to

latch in an off state.

During the capacitor charging period, the dv/dt of the

capacitor is:

dvńdt

+

ILIMIT

CLOAD

Faults

Once the load capacitance is charged, the SENSEFET

will become fully enhanced as long as the current does not

reach the current limit threshold, or is shut−down due to an

overvoltage, undervoltage or thermal fault. Both the

UVLO and OVLO circuits incorporate hysteresis to assure

clean turn−on and turn−offs with no chatter. The thermal

latching circuit will require the input power to be recycled

to resume operation after a fault. The current limit is always

active, so any transient or overload will always be limited.

Circuit Description

Undervoltage Lockout: The UVLO circuit holds the chip

off when the input voltage is less than the turn−on limit. It

includes internal hysteresis to assure clean on/off

switching. An internal divider sets the turn−on voltage

level at 46 V. This voltage can be reduced by adding an

external resistor from the UVLO pin to the Input + pin. The

equivalent circuit is shown in Figure 17.

Input +

UVLO/

ENABLE

RUVLO

200 k

100 k

Vreg

12.5 V

Vz

ZD1

Drain

50 k

Input −

Figure 17. Undervoltage Lockout Circuit

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