1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
18   ______________________________________________________________________________________
Optional Sense Resistor
Select the sense resistor in conjunction with R
CB
to set
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
RSENSE
=
(I
OVERLOAD
)
2
x R
SENSE
; if autoretry is selected, then
P
RSENSE
= (I
OVERLOAD
)
2
x R
SENSE
x (t
ON
/t
RETRY
).
Choose a sense-resistor power rating of twice the
P
RSENSE
for long-term reliable operation. In addition,
ensure that the sense resistor has an adequate I
2
T rating
to survive instantaneous short-circuit conditions.
No-Load Operation
The internal circuitry is capable of sourcing a current at
the OUT terminal of up to 120礎 from a voltage V
IN
+
V
GS
. If there is no load on the circuit, the output capacitor
will charge to a voltage above V
IN
until the external MOS-
FETs body diode conducts to clamp the capacitor volt-
age at VIN plus the body-diode V
F
. When testing or
operating with no load, it is therefore recommended that
the output capacitor be paralleled with a resistor of value:
R = V
X
/ 120礎
where V
X
is the maximum acceptable output voltage
prior to hot-swap completion.
Design Procedure
Given:
" V
CC
= V
S
= 5V
" C
L
= 150礔
" Full-Load Current = 5A
" No R
SENSE
" I
INRUSH
= 500mA
Procedures:
1) Calculate the required slew rate and corresponding
C
SLEW
:
2) Select a MOSFET and determine the worst-case
power dissipation.
3) Minimize power dissipation at full load current and
at high temperature by selecting a MOSFET with an
appropriate R
DS(ON)
. Assume a 20癈 temperature
difference between the MAX5924/MAX5925/
MAX5926 and the MOSFET.
For example, at room temperature the IRF7822s
R
DS(ON)
= 6.5m&. The temperature coefficient for
this device is 4000ppm/癈. The maximum R
DS(ON)
for the MOSFET at T
J(MOSFET)
= +105癈 is:
The power dissipation in the MOSFET at full load is:
4) Select R
CB
.
Since the MOSFETs temperature coefficient is
4000ppm/癈, which is greater than TC
ICB
(3300ppm/癈), 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).
I
TRIPSLOW
= I
FULL LOAD
+ 20% = 5A + 20% = 6A
R
DS(ON)105
= 8.58m& (max), from step 2
I
CB85
= 58礎 x (1 + (3300ppm/癈 x (85 - 25)癈)
= 69.5礎 (min)
R
CB
= ((6A x 8.58m&) + 4.7mV)/69.5礎 = 808&
R
I
x R
V
I
CB
TRIPSLOW
DS ON
CB OS
CB
=
(
)
+
(    )
,
105
85
P    I R
A
m
mW
D
=
=
?/DIV>
& =
2
2
5
8 58
215
(   )        .
R
m
C
C
ppm
C
m
DS ON
(    )
.
   
(
)    
.
105
6 5
1   105
25
4000
8 58
=
?/DIV>
+
?nbsp      ?nbsp   ?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
=
&
&
C
SR
F
SLEW
V
ms
=
?/DIV>
=
?/DIV>
=
330    10
330    10
3 3
0 1
9
9
  
  
.
. ?/DIV>
SR
I
C
V
ms
INRUSH
L
=
?/DIV>
=
1000
3 3
  
.
Table 4. Component Manufacturers
COMPONENT
MANUFACTURER
PHONE
WEBSITE
Dale-Vishay
402-564-3131
www.vishay.com
Sense Resistors
IRC
828-264-8861
www.irctt.com
Fairchild
888-522-5372
www.fairchildsemi.com
MOSFETs
International Rectifier
310-233-3331
www.irf.com
相關代理商/技術參數(shù) |
參數(shù)描述 |
MAX5926EEE+ |
功能描述:熱插拔功率分布 1-13.2V Hot-Swap Controller RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
MAX5926EEE+T |
功能描述:熱插拔功率分布 1-13.2V Hot-Swap Controller RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
MAX5926EEE-T |
功能描述:熱插拔功率分布 RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |
MAX5926EVKIT |
制造商:Maxim Integrated Products 功能描述:1V TO 13.2V N-CHANNEL HOT-SWAP CON - Rail/Tube |
MAX5927AETJ+ |
功能描述:熱插拔功率分布 Quad Hot-Swap Controller RoHS:否 制造商:Texas Instruments 產(chǎn)品:Controllers & Switches 電流限制: 電源電壓-最大:7 V 電源電壓-最小:- 0.3 V 工作溫度范圍: 功率耗散: 安裝風格:SMD/SMT 封裝 / 箱體:MSOP-8 封裝:Tube |