HV302 Supertex Inc, HV302 Datasheet - Page 8

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

Design Information-
The inrush current limit can be calculated as follows:
Thus the inrush current limit for a 2A circuit breaker:
Compensation components from gate to source of the external
MOSFET may be required to reduce peaking of the inrush current.
Compensation can be accomplished as follows:
Servo Mode Timing
1.
2.
3.
Supertex, Inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 TEL: [phone] Fax: [phone] www.supertex.com
Start with a 2nF capacitor from gate to source.
Increase capacitor value up to 10nF if needed.
If needed, add a 1k
capacitor.
I
I
CL
CL
V
50mV
50mΩ
R
SENSE
SENSE
-
CL
1A
R
50mV
SENSE
continued
resistor in series with the above
8
The timing functions are defined by the following equations:
These equations assume that the load is purely capacitive and the
following definitions apply.
These equations may be used to calculate the minimum value of
C
For maximum contact bounce duration protection choose a value
for t
If control of PWRGD active delay is the critical system parameter,
then choose a value for t
RAMP
POR
C
I
10 A, when the voltage drop on R
V
from 9V to 11V.
V
transistor and may be obtained from its datasheet.
V
required to obtain the limit current. It is dependent on the
pass transistor’s characteristics and may be obtained from
the transfer characteristics on the transistor datasheet.
g
may be obtained from its datasheet.
R
I
resistor is 50mV.
RAMP
LIMIT
fs
for the most critical system performance characteristics.
INT
GS(th)
GS(limit)
RAMP
FB
and use the following equation:
is the transconductance of the external pass transistor and
is the internal feedback resistor and is nominally 5K .
is the internally regulated supply voltage and can range
t
t
t
t
t
t
is the load current when the voltage drop on R
C
C
is the output current from the RAMP pin, nominally
START
TH
POR
RISE
LIMIT
PWRGD
is the external capacitor connected to the RAMP pin.
is the gate threshold voltage of the external pass
RAMP
RAMP
is the external pass transistor gate-source voltage
V
t
GS
g
V
A
START
2
fs
IN
2
V
(
4 .
th




t
Rev. D
4 .
INT
POR
t
)
C
. 0
PWRGD
I
V
C
LIMIT
C
I
I
LOAD
I
RAMP
INT
RAMP
I 9
RAMP
RAMP
RAMP
PWRGD-A
V
t
LIMIT
V
C
TH
I
GS
RAMP
GS
RAMP
V
(lim
A
(lim
GS
) it
I
) it
R
(
RAMP
and use the following equation:
LIMIT
R
SENSE
1
FB
)
2 .
1




SENSE
2 .
C
HV302 / HV312
I
RAMP
resistor is zero.
RAMP
04/17/02
SENSE