HV100K5-G(2013) 데이터 시트보기 (PDF) - Supertex Inc

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HV100K5-G
(Rev.:2013)

3-Pin Hotswap, Inrush Current Limiter Controllers (Negative Supply Rail)

Supertex Inc 

HV100

For most applications and pass elements, the HV100 provides

adequate limiting of the maximum current to prevent damage

without the need for any external components. The 2.5s delay

of the auto-retry circuit provides time for the pass element to

cool between attempts.

Auto-Retry

Not only does the HV100 provide short circuit protection in a

3-pin package, they also includes a 2.5s built in auto-restart

timer. The HV100 will continuously try to turn on the system

every 2.5s, providing sufficient time for the pass element to

cool down after each attempt.

This is a surprisingly consistent result because for most

MOSFETs of a particular type the ratio of CISS / CRSS is rela-

tively constant (though notice from the plot that there is some

variation) even while the absolute value of these and other

quantities vary. Based on this, the inrush current will vary

primarily with CLOAD. This makes designing with the HV100

particularly easy because once the pass element is chosen,

the period is fixed and the inrush varies with CLOAD only.

Programming the HV100

The HV100 requires no external components other than a

pass element to provide the functionality described thus far.

In some applications it may be useful to use external compo-

nents to adjust the maximum allowable inrush current, adjust

UVLO, or to provide additional GATE clamping if the supply

rails have rise times below 1.0ms.

All of the above are possible with a minimum number of ex-

ternal components.

i) To adjust inrush current with an external component

simply connect a capacitor (CFB) from drain to GATE of

the MOSFET. The inrush calculation then becomes:

IINRUSH(PEAK) = (CFB + CISS)/(CRSS + CFB) * 2.5e3 * CLOAD

Calculating Inrush Current

As can be seen in the diagram below, for a standard pass

element, the HV100 will normalize the hotswap time period

against load capacitance. For this reason the current limit will

increase with increasing value of the load capacitance.

Note that a resistor (approximately 10KΩ) needs to be

added in series with CFB to create a zero in the feedback

loop and limit the spurious turn on which is now enhanced

by the larger divider element.

ii) To increase undervoltage lockout simply connect a Zener

diode in series with the VPP pin.

iii) If the VPP rises particularly fast (>48e6V/s) then it may be

desirable to connect a capacitor from GATE to source

of the MOSFET to provide a path for the power applica-

tion transient spike, which is now too fast for the internal

clamping mechanism.

iv) To limit the peak current during a short circuit, a resistor

in series with the source of the MOSFET may help.

Inrush can be calculated from the following formula:

IINRUSH(PEAK) = (CISS / CRSS) * 2.5e3 * CLOAD

Doc.# DSFP-HV100

B060513

Supertex inc.

6

www.supertex.com

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