max5924deubt Maxim Integrated Products, Inc., max5924deubt Datasheet - Page 18

• Manufacturer Part Number: max5924deubt
• Description: 1v To 13.2v, N-channel Hot-swap Controllers Require No Sense Resistor
• Manufacturer: Maxim Integrated Products, Inc.

Select the sense resistor in conjunction with R
the slow and fast circuit-breaker thresholds (see the
Selecting a Circuit-Breaker Threshold section). The
sense-resistor power dissipation depends on the device
configuration. If latched mode is selected, P
(I
P
Choose a sense-resistor power rating of twice the
P
ensure that the sense resistor has an adequate I
to survive instantaneous short-circuit conditions.
The internal circuitry is capable of sourcing a current at
the OUT terminal of up to 120µA from a voltage V
V
will charge to a voltage above V
FET’s body diode conducts to clamp the capacitor volt-
age at VIN plus the body-diode V
operating with no load, it is therefore recommended that
the output capacitor be paralleled with a resistor of value:
where V
prior to hot-swap completion.
Given:
Procedures:
1) Calculate the required slew rate and corresponding
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Table 4. Component Manufacturers
18
Sense Resistors
MOSFETs
OVERLOAD
RSENSE
GS
RSENSE
COMPONENT
C
. If there is no load on the circuit, the output capacitor
V
C
Full-Load Current = 5A
No R
I
______________________________________________________________________________________
SLEW
INRUSH
CC
L
= 150µF
X
= V
SENSE
for long-term reliable operation. In addition,
:
= (I
is the maximum acceptable output voltage
)
S
2
= 500mA
SR
OVERLOAD
= 5V
x R
SENSE
1000
R = V
I
INRUSH
International Rectifier
MANUFACTURER
; if autoretry is selected, then
)
X
2
Dale-Vishay
/ 120µA
C
x R
Fairchild
Optional Sense Resistor
L
IRC
IN
SENSE
No-Load Operation
Design Procedure
until the external MOS-
3 3 .
F
. When testing or
ms
V
x (t
ON
RSENSE
/t
CB
2
RETRY
T rating
to set
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IN
PHONE
=
).
+
2) Select a MOSFET and determine the worst-case
3) Minimize power dissipation at full load current and
4) Select R
R
DS ON
I
power dissipation.
at high temperature by selecting a MOSFET with an
appropriate R
difference between the MAX5924/MAX5925/
MAX5926 and the MOSFET.
For example, at room temperature the IRF7822’s
R
this device is 4000ppm/°C. The maximum R
for the MOSFET at T
The power dissipation in the MOSFET at full load is:
Since the MOSFET’s temperature coefficient is
4000ppm/°C, which is greater than TC
(3300ppm/°C), calculate the circuit-breaker thresh-
old at high temperature so the circuit breaker is
guaranteed not to trip at lower temperature during
normal operation (Figure 15).
TRIPSLOW
R
C
(
I
DS(ON)
CB85
CB
SLEW
R
R
)
CB
105
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www.irf.com
P
DS(ON)105
= ((6A x 8.58m ) + 4.7mV)/69.5µA = 808
D
= 58µA x (1 + (3300ppm/°C x (85 - 25)°C)
= 69.5µA (min)
CB
= 6.5m . The temperature coefficient for
I R
6 5
8 58
2
= I
.
330
.
.
I
TRIPSLOW
m
FULL LOAD
DS(ON)
m
(
SR
= 8.58m (max), from step 2
5
A
10
)
2
J(MOSFET)
1 105
. Assume a 20°C temperature
9
WEBSITE
x R
(
+ 20% = 5A + 20% = 6A
8 58
.
330
DS ON
I
CB
C
m
(
3 3
85
= +105°C is:
.
25
)
ms
105
10
V
C
215
)
9
mW
4000
V
0 1
CB OS
.
,
ppm
DS(ON)
F
C
ICB