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参数资料
| 型号： | LTC4355CDE |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 电源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO14 |
| 封装： | 4 X 3 MM, PLASTIC, MO-229WGED-3, DFN-14 |
| 文件页数： | 15/16页 |
| 文件大小： | 221K |
| 代理商： | LTC4355CDE |
LTC4355
8
4355f
APPLICATIONS INFORMATION
MOSFET Selection
The LTC4355 drives N-channel MOSFETs to conduct the
load current. The important features of the MOSFETs are
on-resistance RDS(ON), the maximum drain-source voltage
VDSS, and the threshold voltage.
The gate drive for the MOSFET is guaranteed to be greater
than 4.5V when the supply voltage at VOUT is between 9V
and 20V. When the supply voltage at VOUT is greater than
20V, the gate drive is guaranteed to be greater than 10V. The
gate drive is limited to less than 18V. This allows the use
of logic level threshold N-channel MOSFETs and standard
N-channel MOSFETs above 20V. 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
18V. See the circuit in Figure 4 for an example.
The maximum allowable drain-source voltage, BVDSS,
must be higher than the supply voltages. If an input is
connected to GND, the full supply voltage will appear
across the MOSFET.
If the voltage drop across either MOSFET exceeds the
congurable ΔVSD(FLT) fault threshold, the VDSFLT
pin and the
PWRFLT pin corresponding to the fault-
ing channel pull low. The RDS(ON) should be small
enough to conduct the maximum load current
while not triggering a fault, and to stay within the
MOSFET’s power rating at the maximum load current
(I2 RDS(ON)).
Fault Conditions
The LTC4355 monitors fault conditions and shunts current
away from LEDs or optocouplers, turning each one off to
indicate a specic fault condition (see Table 1).
When the voltage drop across the pass transistor is higher
than the congurable ΔVSD(FLT) fault threshold, the internal
pulldown at the
VDSFLT pin and the PWRFLT1 or PWRFLT2
pin corresponding to the faulting channel turns on. The
ΔVSD(FLT) threshold is congured by the SET pin. Tying
SET to GND, tying SET to a 100kΩ resistor connected
to GND, or oating SET congures ΔVSD(FLT) to 250mV,
500mV, or 1.5V respectively.
Conditions that may cause a high voltage across the pass
transistor include: a MOSFET open on the higher supply,
excessive MOSFET current due to overcurrent on the load
or a shorted MOSFET on the lower supply.
The
PWRFLT pins are additionally used to indicate if either
input supply is below its normal regulation range. If the
voltage at the MON1 or MON2 pin is less than VMON(TH),
typically 1.23V, the corresponding
PWRFLT1 or PWRFLT2
pin will pull low. A resistive divider connected to the input
supply drives the MON pin for the corresponding supply,
conguring the
PWRFLT threshold for that supply. Be sure
to account for the tolerance of the MON pin threshold, the
resistor tolerances, and the regulation range of the supply
being monitored. Also, ensure that the voltage on the MON
pin will not exceed 12V.
The
FUSEFLT pins are used to indicate the status of the
input fuses. If one of the IN pins falls below VINx(TH), typi-
cally 3.5V, the
FUSEFLT pin corresponding to that supply
will pull low. The IN pins each sink a minimum of 0.5mA,
enough to pull the pin low after an input fuse blows open.
If there is a possibility that the MOSFET leakage current
can be greater than 0.5mA, a resistor can be connected
between the IN pin and GND to sink more current. Note
that if the input supply voltage is less than VINx(TH) the
FUSEFLT pin will pull low.
Table 1. Fault Table
ΔVSD1
< ΔVSD(FLT)
VIN1
> 3.5V
VMON1
> 1.23V
VDSFLT* FUSEFLT1 PWRFLT1
True
Hi-Z
True
False
Hi-Z
Pulldown
True
False
True
Hi-Z
Pulldown
Hi-Z
True
False
Hi-Z
Pulldown
False
True
Pulldown
Hi-Z
Pulldown
False
True
False
Pulldown
Hi-Z
Pulldown
False
True
Pulldown
False
Pulldown
*ΔVSD2 < ΔVSD(FLT)
System Power Supply Failure
The LTC4355 automatically supplies load current from
the system input supply with the higher voltage. If this
supply shorts to ground, reverse current begins to ow
through the pass transistor temporarily and the transis-
tor begins to turn off. When this reverse current creates
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| LTC4355CMS#TRPBF | 功能描述:IC IDEAL DIODE-OR DUAL 16-MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - O 圈控制器 系列:- 标准包装:1,000 系列:- 应用:电池备份，工业/汽车，大电流开关 FET 型:- 输出数:5 内部开关:是 延迟时间 - 开启:100ns 延迟时间 - 关闭:- 电源电压:3 V ~ 5.5 V 电流 - 电源:250µA 工作温度:0°C ~ 70°C 安装类型:表面贴装 封装/外壳:16-SOIC（0.154"，3.90mm 宽） 供应商设备封装:16-SOIC N 包装:带卷 (TR) |
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