HV302 Supertex Inc, HV302 Datasheet - Page 10

• Manufacturer Part Number: HV302
• Description: Sequencing Hotswap Controllers
• Manufacturer: Supertex Inc

Design Information -
Supported External Pass Devices
The HV302 and HV312 are designed to support N-Channel
MOSFETs and IGBTs.
Selection of External Pass Devices
The R
allowable voltage drop at maximum load (I
Hotswap action has been completed.
continuous power dissipation rating (P
determined from the following equation:
The peak power rating (P
current level, which is always the circuit breaker trip set point (I
and on the assumption that a output is shorted. The peak power
rating may be calculated from the following equation:
Given these values an external pass transistor may be selected
from the manufacturers data sheet.
Paralleling External Pass Transistors
Due to variations in threshold voltages and transconductance
characteristics between samples of MOSFETs, reliable 50%
current sharing is not achievable. Some measure of paralleling
may be accomplished by adding resistors in series with the source
of each device; however, it will cause increased voltage drop and
power dissipation.
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 HV302 with
active high PWRGD is recommended where the PWRGD pins of
multiple Hotswap circuits can be connected in a wired OR
configuration.
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
as possible with zero current in the sense traces. The use of
Kelvin connection from SENSE pin and V
ends of the current sense resistor is recommended.
Paralleling of external Pass devices is not recommended!
DS(ON)
Supertex, Inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 TEL: [phone] Fax: [phone] www.supertex.com
P
P
CONT
PEAK
of the device is likely to be selected based on
To Negative
Terminal of
Power Source
EE
R
V
IN
DS
and SENSE pins should be direct and as short
(
ON
I
CB
)
I
PEAK
2
LOAD
Sense Resistor
To
VEE
Pin
) should be based on the highest
(
MAX
continued
To
SENSE
Pin
)
CONT
EE
) of the device can be
pin to the respective
Thus the required
To Source
of MOSFET
LOAD(MAX)
) after the
CB
),
10
Rev. D
HV302 / HV312
04/17/02