-48V Hot-Swap Controllers
with External R
SENSE
10   ______________________________________________________________________________________
If more than 3祍 (typ) deglitch time (t
PHLSENSE
) is
needed to prevent spurious shutdown due to load cur-
rent spikes or noise, a simple lowpass filter can be
used between the SENSE and V
EE
pins as shown in
Figure 9. Resistor R7 and capacitor C3 slow down the
response of the circuit breaker to filter momentary
glitches in the SENSE voltage. The additional delay
time can be estimated with the following equation:
where I
f
is the current in fault condition, I
I
is the initial
current before the fault, and I
CB
is the circuit-breaker
trip current (I
CB
= V
CB
/R1). Alternatively, the corre-
sponding voltages across the sense resistor (V
f
, V
I
, and
V
CB
) may be used in the equation as shown. The
SENSE pin of the MAX5948A/MAX5948B sources very
little current (0.02礎 typ), so the addition of resistor R7
will introduce very little error in the circuit-breaker trip
voltage. For example, a 10k& resistor for R7 will only
cause a 200礦 offset.
Example: A system has a 1A nominal load current and
a 20m& sense resistor. The circuit-breaker delay needs
to be increased to 50祍 in response to a load current
step to 5A. The circuit-breaker trip current is
50mV/20m& = 2.5A. Solving for R7 x C3 in the equation
above yields a desired time constant of 100祍. This can
be achieved with R7 = 100& and C3 = 1礔.
t
R   C   In
V   V
V   V
R   C   In
I   I
I   I
cbdly
f
I
f
CB
f    I
f    CB
=   ?nbsp   ?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
=   ?nbsp   ?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
7    3
7    3
GATE - V
EE
5V/div
V
EE
50V/div
INRUSH
CURRENT
2A/div
4ms/div
CONTACT
BOUNCE
Figure 8. Startup Into a Short Circuit
V
EE
SENSE
GATE
DRAIN
V
DD
OV
UV
PWRGD
MAX5948A
-48V RTN
-48V
R4
562k&
1%
R5
9.09k&
1%
R6
10k&
1%
R1
0.02&
5%
R3
18k&
5%
R2
10&
5%
C1
150nF
25V
Q1
IRF530
C2
3.3nF
100V
C4
100礔
100V
*
-48V RTN
(SHORT PIN)
*DIODES INC. SMAT70A.
C3
R7
Figure 9. Extending the Short-Circuit Protection Delay
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
MAX5949AESA |
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 |
MAX5949AESA+ |
功能描述:熱插拔功率分布 48V- 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 |
MAX5949AESA+T |
功能描述:熱插拔功率分布 48V- 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 |
MAX5949AESA+TG126 |
制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
MAX5949AESA-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 |