參數(shù)資料
型號(hào)： LTC4251IS6
廠商： LINEAR TECHNOLOGY CORP
元件分類(lèi)： 電源管理
英文描述： 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO6
封裝： 1 MM HEIGHT, PLASTIC, MO-193, TSOT-23, 6 PIN
文件頁(yè)數(shù)： 3/20頁(yè)
文件大小： 235K
代理商： LTC4251IS6
LTC4251/LTC4251-1/
LTC4251-2
11
425112fa
1. 5.8
A slow charge; initial timing delay
2. 230
A fast charge; circuit breaker delay
3. 5.8
A slow discharge; circuit breaker “cool-off”
4. Low impedance switch; resets capacitor after initial
timing delay, in undervoltage lockout, and in overvolt-
age
For initial startup, the 5.8
A pull-up is used. The low
impedance switch is turned off and the 5.8
A current
source is enabled when the four interlock conditions are
met. CT charges to 4V in a time period given by:
t
VC
A
T
=
4
58
.
(1)
When CT reaches 4V (VTMRH), the low impedance switch
turns on and discharges CT. The GATE output is enabled
and the load turns on.
CIRCUIT BREAKER TIMER OPERATION
If the SENSE pin detects more than 50mV across RS, the
TIMER pin charges CT with 230A. If CT charges to 4V, the
GATE pin pulls low and the LTC4251/LTC4251-1/
LTC4251-2 latch off. The part remains latched off until
either the UV/OV pin is momentarily pulsed low, or VIN
dips into UVLO and is then restored. The circuit breaker
timeout period is given by
t
VC
A
T
=
4
230
(2)
Intermittent overloads may exceed the 50mV threshold at
SENSE, but if their duration is sufficiently short TIMER will
not reach 4V and the LTC4251/LTC4251-1/LTC4251-2
will not latch off. To handle this situation, the TIMER
discharges CT slowly with a 5.8A pull-down whenever the
SENSE voltage is less than 50mV. Therefore any intermit-
tent overload with an aggregate duty cycle of 2.5% or more
will eventually trip the circuit breaker and latch off the
LTC4251/LTC4251-1/LTC4251-2. Figure 3 shows the cir-
cuit breaker response time in seconds normalized to 1
F.
The asymmetric charging and discharging of CT is a fair
gauge of MOSFET heating.
APPLICATIO S I FOR ATIO
WU
UU
The R1-R2 divider values shown in the Typical Application
set a standing current of slightly more than 100
A, and
define an impedance at UV/OV of 30k. In most applica-
tions, 30k impedance coupled with 300mV UV hysteresis
makes the LTC4251/LTC4251-1/LTC4251-2 insensitive to
noise. If more noise immunity is desired, add a 1nF to 10nF
filter capacitor from UV/OV to VEE.
The UV and OV trip point thresholds for the LTC4251-1 are
designed to encompass the standard telecom operating
range of –36V to –72V.
A divider (R1, R2) is used to scale the supply voltage.
Using R1 = 442k and R2 = 34.8k gives a typical operating
range of 33.2V to 81V. The typical under- and overvoltage
shutdown thresholds are then 29.6V and 84.5V. 1%
divider resistors are recommended to preserve threshold
accuracy.
The R1-R2 divider values shown in the Typical Application
set a standing current of slightly more than 100
A, and
define an impedance at UV/OV of 32k. In most applica-
tions, 32k impedance coupled with 260mV UV hysteresis
makes the LTC4251-1 insensitive to noise. If more noise
immunity is desired, add a 1nF to 10nF filter capacitor from
UV/OV to VEE.
UV/OV OPERATION
A low input to the UV comparator will reset the chip and
pull the GATE and TIMER pins low. A low-to-high UV
transition will initiate an initial timing sequence if the three
remaining interlock conditions are met.
Overvoltage conditions detected by the OV comparator
will also pull GATE low, thereby shutting down the load,
but it will not reset the circuit breaker latch. Returning the
supply voltage to an acceptable range restarts the GATE
pin provided all interlock conditions except TIMER are
met.
TIMER
The operation of the TIMER pin is somewhat complex as
it handles several key functions. A capacitor, CT, is used at
TIMER to provide timing for the LTC4251/LTC4251-1/
LTC4251-2. Four different charging and discharging modes
are available at TIMER:
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參數(shù)描述
LTC4251IS6#PBF 制造商:Linear Technology 功能描述:Hot Swap Controller 1-CH 6-Pin TSOT-23
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LTC4251IS6#TRM 功能描述:IC CNTRLR HOTSWAP NEGVOLT SOT236 RoHS:否 類(lèi)別:集成電路 (IC) >> PMIC - 熱交換 系列:- 標(biāo)準(zhǔn)包裝:50 系列:- 類(lèi)型:熱交換控制器 應(yīng)用:-48V 遠(yuǎn)程電力系統(tǒng)，AdvancedTCA ? 系統(tǒng)，高可用性 內(nèi)部開(kāi)關(guān):無(wú) 電流限制:可調(diào) 電源電壓:11.5 V ~ 14.5 V 工作溫度:-40°C ~ 85°C 安裝類(lèi)型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬） 供應(yīng)商設(shè)備封裝:10-MSOP 包裝:管件
LTC4251IS6#TRMPBF 功能描述:IC CTRLR HOTSWAP NEGVOLT SOT23-6 RoHS:是 類(lèi)別:集成電路 (IC) >> PMIC - 熱交換 系列:- 標(biāo)準(zhǔn)包裝:50 系列:- 類(lèi)型:熱交換控制器 應(yīng)用:-48V 遠(yuǎn)程電力系統(tǒng)，AdvancedTCA ? 系統(tǒng)，高可用性 內(nèi)部開(kāi)關(guān):無(wú) 電流限制:可調(diào) 電源電壓:11.5 V ~ 14.5 V 工作溫度:-40°C ~ 85°C 安裝類(lèi)型:表面貼裝 封裝/外殼:10-TFSOP，10-MSOP（0.118"，3.00mm 寬） 供應(yīng)商設(shè)備封裝:10-MSOP 包裝:管件
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