20
LTC4221
4221fa
Timer Function
The TIMER pin controls the initial cycle and the channel
start-up cycles with an external capacitor, C
TIMER
. There
are two comparator thresholds: V
TMR(H)
(1.234V) and
V
TMR(L)
(0.4V). In addition, the pin has a 1.9糀 pull-up
current, a 20糀 pull-up current and a N-channel MOSFET
pull-down.
Initial Timing Cycle
When the card is being inserted into the bus connector, the
long pins mate first which brings up the supplies at time
point 1 of Figure 13. The LTC4221 is in reset mode as the
ON1 pin is low. Both GATE pins and the TIMER pin are
pulled low. At time point 2, the short pin makes contact and
both ON pins are pulled high. At this instant, a start-up
check requires that both supply voltages be above UVLO,
at least one ON pin be above 0.851V, both GATE pins
< 0.4V and TIMER < 0.4V. When these four conditions are
fulfilled, the initial cycle begins and the TIMER pin is pulled
high with 1.9糀. At time point 3, the TIMER reaches
V
TMR(H)
and is pulled down below V
TMR(L)
by the N-
channel MOSFET pull-down, ending the initial cycle at time
point 4. The initial cycle delay is:
t
V
C
A
INITIAL
TIMER
=
?/DIV>
1 234
1 9
.
"
.
(9)
At time point 4, the LTC4221 checks whether the FILTER
pin is <1.24V and FAULT is > 0.851V. If both conditions are
met, a channel start-up cycle commences.
Start-Up Cycle Without Current Limit
During a channel start-up cycle, the TIMER pin ramps up
with a 20糀 internal pull-up so the start-up cycle delay is:
t
V
V
C
A
STARTUP
TIMER
=
(
)
?/DIV>
1 234 0 4
20
.
.
"
(10)
At the beginning of the start-up timing cycle (time point 4),
the LTC4221s electronic circuit breaker is armed and each
channel has an internal 9.5糀 current source working with
an internal charge pump to provide the gate drive to its
external pass transistor. At time point 5, GATE1 reaches
the external pass transistor threshold and V
OUT1
starts to
follow the GATE1 ramp-up. If the inrush current is below
current limit, GATE1 ramps at a constant rate of:
?/DIV>
?/DIV>
=
V
T
I
C
GATE
GATE
GATE
(11)
where C
GATE
is the total capacitance at the GATE1 pin. The
inrush current through R
SENSE1
can be divided into two
components; I
CLOAD
due to the total load capacitance
C
LOAD
and I
LOAD
due to the noncapacitive load elements.
The load bypass capacitance typically dominates C
LOAD
.
For a successful channel start-up without current limit,
I
INRUSH
< active current limit. Due to the voltage follower
configuration, the V
OUT1
ramp rate approximately tracks
V
GATE1
. The inrush current during a start-up cycle without
current limit is :
I
C
V
T
I
I
C
V
T
I
I
C
I
C
I
INRUSH
LOAD
OUT
LOAD
INRUSH
LOAD
GATE
LOAD
INRUSH
LOAD
GATE
GATE
LOAD
=
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
+
=
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
+
=
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
?/DIV>
+
"
"
"
(12)
At time point 6, V
OUT1
is approximately V
CC1
but GATE1
ramp-up continues until it reaches a maximum voltage.
This maximum voltage is determined either by the charge
pump or the internal clamp.
APPLICATIO S I FOR ATIO
U
U
U
1.234V
V
CCn
V
OUT1
ONn
TIMER
GATE1
RESET
STATE
INITIAL
TIMING
CHANNEL 1
START-UP
NORMAL
20糀
9.5糀
0.4V
V
TH
DISCHARGE
BY LOAD
4221 F13
0.851V
0.4V
1 2
3 4 5
6
7
1.9糀
Figure 13. Channel 1 Start-Up Without Current Limit
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
LTC4222CG#PBF
IC CTRLR DUAL HOT SWAP 36-SSOP
LTC4223CDHD-2#PBF
IC CNTRLR HOT SWAP DUAL 16-DFN
LTC4224IDDB-2#TRPBF
IC CNTRLR HOT SWAP DUAL 10-DFN
LTC4225IGN-1#PBF
IC CONTROLLER HOT SWAP 24-SSOP
LTC4230CGN#TRPBF
IC CONTRLLR HOT SWAP TRPL 20SSOP
LTC4232CDHC#TRPBF
IC CTLR HOT SWAP 5A 16-DFN
LTC4240IGN#TRPBF
IC CTRLR HOTSWAP CPCI I2C 28SSOP
LTC4241IGN#PBF
IC CTRLR HOTSWAP 3.3V AUX 20SSOP
相关代理商/技术参数
LTC4222
制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Hot Swap Controller
LTC4222_12
制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Hot Swap Controller
LTC4222CG#PBF
功能描述:IC CTRLR DUAL HOT SWAP 36-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 热交换 系列:- 标准包装:50 系列:- 类型:热交换控制器 应用:-48V 远程电力系统，AdvancedTCA ? 系统，高可用性 内部开关:无 电流限制:可调 电源电压:11.5 V ~ 14.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽） 供应商设备封装:10-MSOP 包装:管件
LTC4222CG#TRPBF
功能描述:IC CTRLR DUAL HOT SWAP 36-SSOP 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)
LTC4222CG-TRPBF
制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Hot Swap Controller with I2C Compatible Monitoring
LTC4222CUH#PBF
功能描述:IC CTRLR DUAL HOT SWAP 32-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)
LTC4222CUH#TRPBF
功能描述:IC CTRLR DUAL HOT SWAP 32-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)
LTC4222CUH-PBF
制造商:LINER 制造商全称:Linear Technology 功能描述:Dual Hot Swap Controller with I2C Compatible Monitoring