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| 型号： | LTC4252A-2CMS#TRPBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 电源管理 |
| 英文描述： | Negative Voltage Hot Swap Controllers; Package: MSOP; No of Pins: 10; Temperature Range: 0°C to +70°C |
| 中文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO10 |
| 封装： | LEAD FREE, PLASTIC, MSOP-10 |
| 文件页数： | 10/36页 |
| 文件大小： | 394K |
| 代理商： | LTC4252A-2CMS#TRPBF |
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LTC4252-1/LTC4252-2
LTC4252A-1/LTC4252A-2
18
425212fb
and eliminates current spikes at insertion. A large external
gate-source capacitor is thus unnecessary for the purpose
of compensating CGD. Instead, a smaller value (≥ 10nF)
capacitor CC is adequate. CC also provides compensation
for the analog current limit loop.
GATE has two comparators: the GATE low comparator
looks for < 0.5V threshold prior to initial timing or a GATE
start-up cycle; the GATE high comparator looks for < 2.8V
relative to VIN and, together with the DRAIN low compara-
tor, sets PWRGD status during GATE startup.
SENSE
The SENSE pin is monitored by the circuit breaker (CB)
comparator, the analog current limit (ACL) amplifier and
the fast current limit (FCL) comparator. Each of these three
measures the potential of SENSE relative to VEE. When
SENSE exceeds 50mV, the CB comparator activates the
230
ATIMERpull-up.At100mV(60mVfortheLTC4252A),
the ACL amplifier servos the MOSFET current and, at
200mV, the FCL comparator abruptly pulls GATE low in an
attempt to bring the MOSFET current under control. If any
of these conditions persists long enough for TIMER to
charge CT to 4V (see Equation 3), the LTC4252 shuts
down and pulls GATE low.
If the SENSE pin encounters a voltage greater than VACL,
the ACL amplifier will servo GATE downwards in an
attempt to control the MOSFET current. Since GATE over-
drives the MOSFET in normal operation, the ACL amplifier
needs time to discharge GATE to the threshold of the
MOSFET. For a mild overload the ACL amplifier can control
the MOSFET current, but in the event of a severe overload
the current may overshoot. At SENSE = 200mV the FCL
comparator takes over, quickly discharging the GATE pin
to near VEE potential. FCL then releases and the ACL
amplifier takes over. All the while TIMER is running. The
effect of FCL is to add a nonlinear response to the control
loop in favor of reducing MOSFET current.
Owing to inductive effects in the system, FCL typically
overcorrects the current limit loop and GATE under-
shoots. A zero in the loop (resistor RC in series with the
gate capacitor) helps the ACL amplifier to recover.
SHORT-CIRCUIT OPERATION
Circuit behavior arising from a load side low impedance
short is shown in Figure 6 for the LTC4252. Initially, the
current overshoots the fast current limit level of VSENSE =
200mV (Trace 2) as the GATE pin works to bring VGS under
control (Trace 3). The overshoot glitches the backplane in
the negative direction and when the current is reduced to
100mV/RS, the backplane responds by glitching in the
positive direction.
TIMER commences charging CT (Trace 4) while the analog
current limit loop maintains the fault current at 100mV/RS,
which in this case is 5A (Trace 2). Note that the backplane
voltage (Trace 1) sags under load. Timer pull-up is accel-
erated by VOUT. When CT reaches 4V, GATE turns off,
PWRGD pulls high, the load current drops to zero and the
backplane rings up to over 100V. The transient associated
with the GATE turn off can be controlled with a snubber to
reduce ringing and a transient voltage suppressor (such
as Diodes Inc. SMAT70A) to clip off large spikes. The choice
of RC for the snubber is usually done experimentally. The
value of the snubber capacitor is usually chosen between
10 to 100 times the MOSFET COSS. The value of the snub-
ber resistor is typically between 3
to 100.
APPLICATIO S I FOR ATIO
WU
U
Figure 6. Output Short-Circuit Behavior of LTC4252
4252-1/2 F06
–48RTN
50V/DIV
GATE
10V/DIV
SENSE
200mV/DIV
TIMER
5V/DIV
0.5ms/DIV
FAST CURRENT LIMIT
SUPPLY RING OWING TO
CURRENT OVERSHOOT
SUPPLY RING OWING TO
MOSFET TURN OFF
ANALOG CURRENT LIMIT
ONSET OF OUTPUT SHORT-CIRCUIT
CTIMER RAMP
LATCH OFF
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| LTC4252A-2IMS | 功能描述:IC CTRLR HOTSWAP NEG VOLT 10MSOP 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 |
| LTC4252A-2IMS#PBF | 功能描述:IC CNTRLR HOTSWAP NEGVOLT 10MSOP 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 |
| LTC4252A-2IMS#TR | 功能描述:IC CTRLR HOTSWAP NEG VOLT 10MSOP 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 |
| LTC4252A-2IMS#TRPBF | 功能描述:IC CNTRLR HOTSWAP NEGVOLT 10MSOP 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 |
| LTC4252A-2IMSPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:Negative Voltage Hot Swap Controllers |
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