LTC4211
22
4211fb
OPERATION
SENSE RESISTOR CONSIDERATIONS
The fault current level at which the LTC4211s internal
electronic circuit breaker trips is determined by a sense
resistor connected between the LTC4211s V
CC
and SENSE
pins and two separate trip points. The first trip point is
set by the SLOW COMPs threshold, V
CB(SLOW)
= 50mV,
and occurs should a load current fault condition exist for
more than 20約. The current level at which the electronic
circuit breaker trips is given by Equation 8:
  
I
TRIP(SLOW)
=
V
CB(SLOW)
R
SENSE
=
50mV
R
SENSE
(8)
The second trip point is set by the FAST COMPs threshold,
V
CB(FAST)
= 150mV, and occurs during fast load current
transients that exist for 300ns or longer. The current level
at which the circuit breaker trips in this case is given by
Equation 9:
TRIP(FAST)
=
V
CB(FAST)
R
EN E
=
150mV
R
EN E
(9)
As a design aid, the currents at which the electronic circuit
breaker trips for common values for R
SENSE
are shown
in Table 3.
Figure 11. Making PCB Connections to the Sense Resistor
Table 2. t
SLOWCOMP
vs C
FILTER
C
FILTER
t
SLOWCOMP
100pF
82約
220pF
156約
330pF
224約
470pF
310約
680pF
440約
820pF
527約
1000pF
638約
Table 3. I
TRIP(SLOW)
and I
TRIP(FAST)
vs R
SENSE
R
SENSE
I
TRIP(SLOW)
I
TRIP(FAST)
0.005?/DIV>
10A
30A
0.006?/DIV>
8.3A
25A
0.007?/DIV>
7.1A
21A
0.008?/DIV>
6.3A
19A
0.009?/DIV>
5.6A
17A
0.01?/DIV>
5A
15A
For proper circuit breaker operation, Kelvin-sense PCB
connections between the sense resistor and the LTC4211s
V
CC
and SENSE pins are strongly recommended. The
drawing in Figure 11 illustrates the correct way of making
connections between the LTC4211 and the sense resis-
tor. PCB layout should be balanced and symmetrical to
minimize wiring errors. In addition, the PCB layout for the
sense resistor should include good thermal management
techniques for optimal sense resistor power dissipation.
The power rating of the sense resistor should accommodate
steady-state fault current levels so that the component is
not damaged before the circuit breaker trips. Table? in
the Appendix lists sense resistors that can be used with
the LTC4211s circuit breaker.
IRC-TT SENSE RESISTOR
LR251201R010F
OR EQUIVALENT
0.01, 1%, 1W
CURRENT FLOW
TO LOAD
CURRENT FLOW
TO LOAD
TO
V
CC
TO
SENSE
TRACK WIDTH W:
0.03" PER AMP
ON 1 OZ COPPER
W
4211 F11
CALCULATING CIRCUIT BREAKER TRIP CURRENT
For a selected R
SENSE
value, the nominal load current that
trips the circuit breaker is given by Equation 10:
TRIP(NOM)
=
V
CB(NOM)
R
EN E N  M
=
50mV
R
EN E N  M
(10)
The minimum load current that trips the circuit breaker is
given by Equation 11.
TRIP(MIN)
=
V
CB(MIN)
R
EN E MAX
=
40mV
R
EN E MAX
(11)
where
R
SENSE(MAX)
= R
SENSE(NOM)
1+
R
TOL
100
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
相關代理商/技術參數 |
參數描述 |
LTC4211IMS8#PBF |
功能描述:IC CONTROLLER HOT SWAP 8-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 熱交換 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program 標準包裝:119 系列:- 類型:熱交換控制器 應用:通用型,PCI Express? 內部開關:無 電流限制:- 電源電壓:3.3V,12V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:80-TQFP 供應商設備封裝:80-TQFP(12x12) 包裝:托盤 產品目錄頁面:1423 (CN2011-ZH PDF) |
LTC4211IMS8#TR |
功能描述:IC CONTROLLER HOT SWAP 8-MSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 熱交換 系列:- 標準包裝:50 系列:- 類型:熱交換控制器 應用:-48V 遠程電力系統,AdvancedTCA ? 系統,高可用性 內部開關:無 電流限制:可調 電源電壓:11.5 V ~ 14.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP,10-MSOP(0.118",3.00mm 寬) 供應商設備封裝:10-MSOP 包裝:管件 |
LTC4211IMS8#TRPBF |
功能描述:IC CONTROLLER HOT SWAP 8-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 熱交換 系列:- 標準包裝:50 系列:- 類型:熱交換控制器 應用:-48V 遠程電力系統,AdvancedTCA ? 系統,高可用性 內部開關:無 電流限制:可調 電源電壓:11.5 V ~ 14.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:10-TFSOP,10-MSOP(0.118",3.00mm 寬) 供應商設備封裝:10-MSOP 包裝:管件 |
LTC4211IS8 |
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LTC4211IS8#PBF |
功能描述:IC CONTROLLER HOT SWAP 8-SOIC RoHS:是 類別:集成電路 (IC) >> PMIC - 熱交換 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program 標準包裝:119 系列:- 類型:熱交換控制器 應用:通用型,PCI Express? 內部開關:無 電流限制:- 電源電壓:3.3V,12V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:80-TQFP 供應商設備封裝:80-TQFP(12x12) 包裝:托盤 產品目錄頁面:1423 (CN2011-ZH PDF) |
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