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| 型号： | LTC4227IUFD-1#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 电源管理 |
| 英文描述： | POWER SUPPLY MANAGEMENT CKT, PQCC20 |
| 封装： | 4 X 5 MM, PLASTIC, MO-220, QFN-20 |
| 文件页数： | 7/20页 |
| 文件大小： | 307K |
| 代理商： | LTC4227IUFD-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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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC4227IUFD-2#PBF | 功能描述:IC CONTROLLER HOT SWAP 20-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:119 系列:- 类型:热交换控制器 应用:通用型，PCI Express? 内部开关:无 电流限制:- 电源电压:3.3V，12V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:80-TQFP 供应商设备封装:80-TQFP（12x12） 包装:托盘 产品目录页面:1423 (CN2011-ZH PDF) |
| LTC4227IUFD-2#TRPBF | 功能描述:IC CTRLR HOT SWAP 20-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:119 系列:- 类型:热交换控制器 应用:通用型，PCI Express? 内部开关:无 电流限制:- 电源电压:3.3V，12V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:80-TQFP 供应商设备封装:80-TQFP（12x12） 包装:托盘 产品目录页面:1423 (CN2011-ZH PDF) |
| LTC4228-1 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Ideal Diode and Hot Swap Controller |
| LTC4228CGN-1#PBF | 功能描述:IC HOT SWAP CTRLR 28SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:119 系列:- 类型:热交换控制器 应用:通用型，PCI Express? 内部开关:无 电流限制:- 电源电压:3.3V，12V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:80-TQFP 供应商设备封装:80-TQFP（12x12） 包装:托盘 产品目录页面:1423 (CN2011-ZH PDF) |
| LTC4228CGN-1#TRPBF | 功能描述:IC HOT SWAP CTRLR 28SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:119 系列:- 类型:热交换控制器 应用:通用型，PCI Express? 内部开关:无 电流限制:- 电源电压:3.3V，12V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:80-TQFP 供应商设备封装:80-TQFP（12x12） 包装:托盘 产品目录页面:1423 (CN2011-ZH PDF) |
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