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參數(shù)資料
| 型號： | LTC4227CUFD-1#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 電源管理 |
| 英文描述： | POWER SUPPLY MANAGEMENT CKT, PQCC20 |
| 封裝： | 4 X 5 MM, PLASTIC, MO-220, QFN-20 |
| 文件頁數(shù)： | 7/20頁 |
| 文件大?。?/td> | 307K |
| 代理商： | LTC4227CUFD-1#TRPBF |
LTC4227-1/LTC4227-2
15
422712f
applicaTions inForMaTion
greater than 10V. The gate drive is limited to not more than
14V. This allows the use of logic-level threshold N-channel
MOSFETs and standard N-channel MOSFETs above 7V. An
external Zener diode can be used to clamp the potential
from the MOSFET’s gate to source if the rated breakdown
voltage is less than 14V.
The maximum allowable drain-source voltage, BVDSS,
must be higher than the supply voltages as the full sup-
ply voltage can appear across the MOSFET. If an input or
output is connected to ground, the full supply voltage will
appear across the MOSFET. The RDS(ON) should be small
enough to conduct the maximum load current, and also
stay within the MOSFET’s power rating.
CPO Capacitor Selection
Therecommendedvalueofthecapacitor,CCP,betweenthe
CPO and IN pins is approximately 10
× the input capaci-
tance, CISS, of the ideal diode MOSFET. A larger capacitor
takes a correspondingly longer time to charge up by the
internal charge pump. A smaller capacitor suffers more
voltage drop during a fast gate turn-on event as it shares
charge with the MOSFET gate capacitance.
Supply Transient Protection
When the capacitances at the input and output are very
small, rapid changes in current during an input or output
short-circuit event can cause transients that exceed the
24V absolute maximum ratings of the IN and OUT pins.
To minimize such spikes, use wider traces or heavier
trace plating to reduce the power trace inductance. Also,
bypass locally with a 10F electrolytic and 0.1F ceramic,
or alternatively clamp the input with a transient voltage
suppressor (Z1, Z2). A 10Ω, 0.1F snubber damps the
response and eliminates ringing (See Figure 9).
Design Example
As a design example for selecting components, consider
a 12V system with a 7.6A maximum load current for the
two supplies (see Figure 1).
First, select the appropriate value of the current sense re-
sistor, RS, for the 12V supply. Calculate the sense resistor
value based on the maximum load current and the lower
limit for the circuit breaker threshold,
VSENSE(CB)(MIN):
RS =
VSENSE(CB)(MIN)
ILOAD(MAX)
=
47.5mV
7.6A
= 6.25m
Choose a 6mΩ sense resitor with a 1% tolerance. The
minimum and maximum circuit breaker trip current is
calculated as follows:
ITRIP(MIN) =
VSENSE(CB)(MIN)
RS(MAX)
=
47.5mV
6.06m
= 7.8A
ITRIP(MAX) =
VSENSE(CB)(MAX)
RS(MIN)
=
52.5mV
5.94m
= 8.8A
Forproperoperation,ITRIP(MIN)mustexceedthemaximum
load current with margin, so RS = 6mΩ should suffice for
the 12V supply.
Next, calculate the RDS(ON) of the ideal diode MOSFET to
achievethedesiredforwarddropatmaximumload.Assum-
ing a forward drop,
VFWD of 60mV across the MOSFET:
RDS(ON) ≤
VFWD
ILOAD(MAX)
=
60mV
7.6A
= 7.9m
The SiR462DP offers a good choice with a maximum
RDS(ON) of 7.9mΩ at VGS = 10V. The input capacitance,
CISS, of the SiR462DP is about 1155pF. Slightly exceeding
the 10
× recommendation, a 0.1F capacitor is selected
for CCP1 and CCP2 at the CPO pins.
Next, verify that the thermal ratings of the selected Hot
SwapMOSFET,Si7336ADP,arenotexceededduringpower-
up or an output short.
Assuming the MOSFET dissipates power due to inrush
current charging the load capacitor, CL, at power-up, the
energy dissipated in the MOSFET is the same as the energy
stored in the load capacitor, and is given by:
ECL =
1
2
CL VIN2
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| LTC4227CUFD-2#PBF | 功能描述:IC CTRLR HOT SWAP 20-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 熱交換 系列:- 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:100 系列:- 類型:熱插拔開關(guān) 應(yīng)用:通用 內(nèi)部開關(guān):是 電流限制:可調(diào) 電源電壓:9 V ~ 13.2 V 工作溫度:-40°C ~ 150°C 安裝類型:表面貼裝 封裝/外殼:10-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:10-TDFN-EP（3x3） 包裝:管件 |
| LTC4227CUFD-2#TRPBF | 功能描述:IC CTRLR HOT SWAP 20-QFN RoHS:是 類別:集成電路 (IC) >> PMIC - 熱交換 系列:- 產(chǎn)品培訓(xùn)模塊:Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:100 系列:- 類型:熱插拔開關(guān) 應(yīng)用:通用 內(nèi)部開關(guān):是 電流限制:可調(diào) 電源電壓:9 V ~ 13.2 V 工作溫度:-40°C ~ 150°C 安裝類型:表面貼裝 封裝/外殼:10-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:10-TDFN-EP（3x3） 包裝:管件 |
| LTC4227CUFD-3#PBF | 制造商:Linear Technology 功能描述:IC CTRLR HOT SWAP 20QFN 制造商:Linear Technology 功能描述:HOT SWAP CONTROLLER 2.9-18V 制造商:Linear Technology 功能描述:DIODE-OR/HOT SWAP CTRL, 18V, QFN-20, IC Function:Diode-OR and Hot Swap Controlle |
| LTC4227CUFD-3#TRPBF | 制造商:Linear Technology 功能描述:IC CTRLR HOT SWAP 20QFN 制造商:Linear Technology 功能描述:DIODE-OR/HOT SWAP CTRL, 18V, QFN-20, IC Function:Diode-OR and Hot Swap Controlle |
| LTC4227CUFD-4#PBF | 制造商:Linear Technology 功能描述:IC CTRLR HOT SWAP 20QFN 制造商:Linear Technology 功能描述:HOT SWAP CONTROLLER 2.9-18V 制造商:Linear Technology 功能描述:DIODE-OR/HOT SWAP CTRL, 18V, QFN-20, IC Function:Diode-OR and Hot Swap Controlle |
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