NIS5135 查看數據表（PDF） - Diodes Incorporated.

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NIS5135

3.6A 5V RESETTABLE ELECTRONIC FUSE

Diodes Incorporated. 

NOT RECOMMENDED FOR NEW DESIGN

NO ALTERNATE PART

NIS5135

Application Note

Theory of Operation

The NIS5135 is a self-protected, resettable electronic fuse. It monitors the input and output voltage, the output current and the die temperature.

When the NIS5135 is powered up it will ramp up the output voltage based on the dv/dt setting (see description below) and current will begin to flow.

The device current limit can be set with an external resistor, the ramp rate (dv/dt) can be adjusted with an external capacitor. The

Overvoltage Clamp, Undervoltage Lockout and Thermal Protection are internally set.

Power Supply Considerations

Placing a high-value electrolytic capacitor or X7R (X5R) ceramic capacitor between VDD to GND (10µF) and Source to GND (70µF) as close to the

device as possible is highly recommended. This precaution reduces power-supply transients that may cause ringing on the input and load

transients that may cause output voltage falls below input voltage resulting device over-heat.

Current Limit

The NIS5135 incorporates a sensefet with a reference and amplifier to control the current in the device. The sensefet uses a small fraction of the

load current to measure the actual current. This reduces the losses as a smaller sense resistor can be used. The current can be measured

directly with the Rs resistor connected between the load and the ILIMIT pin (see Figure 1). That method includes the resistance of the bond wires

in the current limiting circuit. A Kelvin connection (see Figure 2) can be used also; in that case one of the 5 source pins will be used and the

voltage is measured on the die, eliminating the bond wire resistance. That reduces the Source pins to the load to four and therefore increases the

on-resistance of the effuse to the load.

Overvoltage Clamp

The NIS5135MN1 and NIS5135MN2 monitor the input voltage and clamp it once it exceeds 6.65V. This will allow for transient on the input for

short periods of time. If the input voltage stays above 6.65V for extended time the voltage drop across the FET with the load current will

increase the die temperature and the thermal shutdown feature will protect the device and shut it down.

Undervoltage Lock Out

The input voltage of the NIS5135 is monitored by an UVLO circuit (undervoltage lockout) if the input voltage drops below this threshold the

output transistor will be pulled into a high impedance state.

dv/dt

The NIS5135 has an integrated control circuit that forces a linear ramp on the output voltage raise regardless of the load impedance. Without

connecting a capacitor on the dv/dt pin the ramp time is roughly 2ms. Adding an external capacitor can increase this ramp rate. The internal

current source of 90µA will charge the external capacitor at a slow rate. It is recommended to utilize a ceramic capacitor.

The ramp time can be determined with the following equation:

Cext in Farad

tramp in seconds

The ramp-up circuit is discharged and VOUT starts from 0V when the units shut down after a fault, enable shutdown or input power cycle.

Enable/Fault

The NIS5135 has a tri state Enable/Fault pin. It is used to turn on and off the device with high and low signals from a GPIO, but can also indicate a

thermal fault. When the Enable/Fault pin is pulled low, the output is turned off. When the Enable/Fault pin is pulled high, the output is turned on. In

the event of a thermal fault, the Enable/Fault pin will be pulled low to an intermediate voltage by an internal circuit. This can be used to chain up

to 4 NIS5135 together that during a thermal shut down the linked devices turn off as well.

Due to this fault indication capability, it should not be connected to any type of logic with an internal pull up device.

The NIS5135MN1 connected to a 2nd device will latch off until the Enable/Fault pin has been pulled to low and then allowed to go back up to a

high signal, or if the power has been cycled. Once the part starts up again it will go through the start up ramp determined by the internal circuit or

based on the externally connected capacitor on pin dv/dt.

The MN2 devices will auto restart once the part that indicated a thermal shutdown has cooled down. It will also go through the start up ramp.

NIS5135

Document number: DS37968 Rev. 4 - 3

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www.diodes.com

May 2017

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