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| 型号： | LTC4221CGN#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 21/28页 |
| 文件大小： | 272K |
| 描述： | IC CTLR HOT SWAP DUAL 16SSOP |
| 标准包装： | 100 |
| 类型： | 热交换控制器 |
| 应用： | 通用 |
| 内部开关： | 无 |
| 电源电压： | 1 V ~ 13.5 V |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 供应商设备封装： | 16-SSOP |
| 包装： | 管件 |
| 产品目录页面： | 1342 (CN2011-ZH PDF) |
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21
LTC4221
4221fa
0.4V
V
TH
1.234V
1.9糀
20糀
<9.5糀
9.5糀
9.5糀
DISCHARGE
BY LOAD
4221 F14
0.851V
0.4V
1.234V
1 2
V
CCn
V
ONn
V
TIMER
V
GATE2
V
OUT2
I
RSENSE2
3 4 56
7 8 9
A
REGULATED AT 25mV/R
SENSE
REGULATED AT
V
SENSE(ACL)
(t)/R
SENSE
RESET
STATE
INITIAL
TIMING
CHANNEL 2
START-UP
NORMAL
CYCLE
Start-Up Cycle With Current Limit
During a channel start-up cycle, if the inrush current as
according to Equation (12) is large enough to cause a
voltage drop greater than the active current limit threshold
(V
SENSE(ACL)
) across the sense resistor, an internal servo
loop controls the operation of the 9.5糀 current source at
the GATE pin to regulate the load current to:
I
V
R
INRUSH
SENSE ACL
SENSE
=
( )
(13)
The active current limit threshold for channel n has a
component controlled by the voltage at the FBn pin. When
FBn = 0V, V
SENSE(ACL)
= 9mV. As V
OUTn
and FBn ramp up,
V
SENSE(ACL)
increases linearly until FBn reaches 0.5V,
where V
SENSE(ACL)
saturates at 25mV. In this fashion, the
inrush current is controlled by this foldback limiting that
tends to keep the power dissipation in the external MOSFET
constant during the start-up cycle.
The timing diagram in Figure 14 illustrates the operation of
the LTC4221 in a channel start-up cycle with limited inrush
current as described by Equation 13. Between time points
5 and 6, the GATE2 pin ramps up with I
GATE
= 9.5糀. At
time point 6, the inrush current increases enough to trip
V
SENSE(ACL)
(t) and an internal servo loop engages, limiting
the inrush current to the level as in Equation 13 by
decreasing I
GATE
(<9.5糀). As a result, the ramp rate of
both V
GATE2
and V
OUT2
decreases and V
SENSE2
increases
linearly until it saturates at 25mV at time point 7. At time
point 8, the external MOSFET enters triode operation.
I
INRUSH
drops as the ramp rate of V
OUT2
falls below that of
V
GATE2
so I
GATE
reverts back to 9.5糀. At time point 9, the
internal servo loop to control I
INRUSH
is disengaged and
channel 2 slow comparator is armed, ending the channel 2
start-up cycle. So if C
LOAD2
is not fully charged up at this
point, I
INRUSH
will be subject to the slow comparator
threshold and actions as outlined in the Electronic Circuit
Breaker section. For a successful channel start-up, the
current limited part of the V
OUT
ramp-up (time points 6 and
8 of Figure 14) must not exceed the sum of start-up cycle
delay as given by Equation 10 and the slow comparator
response time as given by Equation 1. An example of an
unsuccessful start-up is Figure 11 which shows a channel
powering up into an overcurrrent at the load.
The fast comparators of both channels are armed at the
end of the initial timing cycle at time point 4 of Figure 14.
If a short circuit during the start-up cycle overrides the
servo loop and causes V
RSENSE
of either channel to exceed
100mV for more than 1約, the electronic circuit breaker
trips and the LTC4221 enters the fault state.
Frequency Compensation at Start-Up Cycle
If a channels external gate input capacitance (C
ISS
) is
greater than 600pF, no external gate capacitor is required
at GATE to stabilize the internal current-limiting loop dur-
ing start-up with current limit. The servo loop that controls
the external MOSFET during current limiting has a unity-
gain frequency of about 105kHz and phase margin of 80?/DIV>
for external MOSFET gate input capacitances to 2.5nF.
Power MOSFET
Power MOSFETs can be classified by R
DS(ON)
at V
GS
gate
drive ratings of 10V, 4.5V, 2.5V and 1.8V. Those rated for
R
DS(ON)
at 10V V
GS
usually have a higher V
GS
absolute
maximum rating than those at 4.5V and 2.5V. At low
APPLICATIO S I FOR ATIO
U
U
U
Figure 14. Channel 2 Start-Up with Current Limit
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| LTC4221IGN | 功能描述:IC CTRLR HOTSWAP DUAL 16SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:100 系列:- 类型:热插拔开关 应用:通用 内部开关:是 电流限制:可调 电源电压:9 V ~ 13.2 V 工作温度:-40°C ~ 150°C 安装类型:表面贴装 封装/外壳:10-WFDFN 裸露焊盘 供应商设备封装:10-TDFN-EP（3x3） 包装:管件 |
| LTC4221IGN#PBF | 功能描述:IC CTRLR HOTSWAP DUAL 16SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:100 系列:- 类型:热插拔开关 应用:通用 内部开关:是 电流限制:可调 电源电压:9 V ~ 13.2 V 工作温度:-40°C ~ 150°C 安装类型:表面贴装 封装/外壳:10-WFDFN 裸露焊盘 供应商设备封装:10-TDFN-EP（3x3） 包装:管件 |
| LTC4221IGN#TR | 功能描述:IC CTRLR HOTSWAP DUAL 16SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:100 系列:- 类型:热插拔开关 应用:通用 内部开关:是 电流限制:可调 电源电压:9 V ~ 13.2 V 工作温度:-40°C ~ 150°C 安装类型:表面贴装 封装/外壳:10-WFDFN 裸露焊盘 供应商设备封装:10-TDFN-EP（3x3） 包装:管件 |
| LTC4221IGN#TRPBF | 功能描述:IC CTRLR HOTSWAP DUAL 16SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:100 系列:- 类型:热插拔开关 应用:通用 内部开关:是 电流限制:可调 电源电压:9 V ~ 13.2 V 工作温度:-40°C ~ 150°C 安装类型:表面贴装 封装/外壳:10-WFDFN 裸露焊盘 供应商设备封装:10-TDFN-EP（3x3） 包装:管件 |
| LTC4222 | 制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Hot Swap Controller |
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