HV311LG datasheet(9/21 Pages) SUTEX

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HV301/HV311

Application Information

Supported External Pass Devices

The HV301 and HV311 are designed to support N-Channel

MOSFETs and IGBTs.

Selection of External Pass Devices

Since the current limit is likely to be set just slightly higher than

maximum continuous load current in a typical system, the

continuous current rating of the device will have to be at least

equal to the current limit value.

The

DS(ON) of the device is likely to be selected based on

allowable voltage drop after the hot swap action has been

completed. Thus the continuous power dissipation rating of the

device can be determined from the following equation:

CONT

DS ON

LIMIT

=×

()

The peak power rating may be calculated from the following

equation:

PEAK

LIMIT

=×

Given these values an external pass transistor may be selected

from the manufacturers data sheet.

Selection of Current Sense Resistor

The power rating of the sense resistor must be greater than

load

, where Iload is the normal maximum operating load.

Kelvin Connection to Sense Resistor

Physical layout of the printed circuit board is critical for correct

current sensing. Ideally trace routing between the current sense

resistor and the V

EE and SENSE pins should be direct and as

short as possible with zero current in the sense traces. The use

of Kelvin connection from SENSE pin and V

EE pin to the respec-

tive ends of the current sense resistor is recommended.

Paralleling External Pass Transistors

Due to variations in threshold voltages and gain characteristics

between samples of transistors reliable 50% current sharing is

not achievable. Some measure of paralleling may be accom-

plished by adding resistors in series with the source of each

device; however, it will cause increased voltage drop and power

dissipation.

Paralleling of external Pass devices is not recommended!

If a sufficiently high current rated external pass transistor cannot

be found then increased current capability may be achieved by

connecting independent hotswap circuits in parallel, since they

act as current sources during the load capacitor charging time

when the circuits are in current limit. For this application the

HV301 with active high PWRGD is recommended where the

PWRGD pins of multiple hot swap circuits can be connected in

a wired OR configuration.

To Negative

Terminal of

Power Source

To Source

of MOSFET

VEE

Sense Resistor

SENSE

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