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參數(shù)資料
| 型號： | LTC4085EDE-3#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 電源管理 |
| 英文描述： | POWER SUPPLY MANAGEMENT CKT, PDSO14 |
| 封裝： | 4 X 3 MM, PLASTIC, MO-229, DFN-14 |
| 文件頁數(shù)： | 7/24頁 |
| 文件大?。?/td> | 275K |
| 代理商： | LTC4085EDE-3#TRPBF |
LTC4085-3
15
40853f
Programming Current Limit
The formula for input current limit is:
ICL =
1000
RCLPROG
VCLPROG
=
1000V
RCLPROG
where VCLPROG is the CLPROG pin voltage and RCLPROG
is the total resistance from the CLPROG pin to ground.
For example, if typical 500mA current limit is required,
calculate:
RCLPROG =
1V
500mA
1000 = 2k
In USB applications, the minimum value for RCLPROG
should be 2.1k. This will prevent the application current
from exceeding 500mA due to LTC4085-3 tolerances
and quiescent currents. A 2.1k CLPROG resistor will
give a typical current limit of 476mA in high power mode
(HPWR = 1) or 95mA in low power mode (HPWR = 0).
VCLPROG will track the input current according to the fol-
lowing equation:
IIN =
VCLPROG
RCLPROG
1000
For best stability over temperature and time, 1% metal
lm resistors are recommended.
Ideal Diode from BAT to OUT
The LTC4085-3 has an internal ideal diode as well as a
controller for an optional external ideal diode. If a battery
is the only power supply available or if the load current
exceeds the programmed input current limit, then the
battery will automatically deliver power to the load via an
ideal diode circuit between the BAT and OUT pins. The
ideal diode circuit (along with the recommended 4.7μF
capacitor on the OUT pin) allows the LTC4085-3 to handle
large transient loads and wall adapter or USB VBUS con-
nect/disconnect scenarios without the need for large bulk
capacitors. The ideal diode responds within a few micro-
seconds and prevents the OUT pin voltage from dropping
signicantly below the BAT pin voltage. A comparison of
the I-V curve of the ideal diode and a Schottky diode can
be seen in Figure 3.
If the input current increases beyond the programmed
input current limit additional current will be drawn from
the battery via the internal ideal diode. Furthermore, if
power to IN (USB VBUS) or OUT (external wall adapter)
is removed, then all of the application power will be pro-
vided by the battery via the ideal diode. A 4.7μF capacitor
at OUT is sufficient to keep a transition from input power
to battery power from causing significant output voltage
droop. The ideal diode consists of a precision amplifier that
enables a large P-Channel MOSFET transistor whenever
the voltage at OUT is approximately 20mV (VFWD) below
the voltage at BAT. The resistance of the internal ideal
diode is approximately 200mΩ. If this is sufficient for the
application then no external components are necessary.
However, if more conductance is needed, an external
PFET can be added from BAT to OUT. The GATE pin of the
LTC4085-3 drives the gate of the PFET for automatic ideal
diode control. The source of the external PFET should be
connected to OUT and the drain should be connected to
BAT. In order to help protect the external PFET in over-
current situations, it should be placed in close thermal
contact to the LTC4085-3.
FORWARD VOLTAGE (V)
(BAT-OUT)
CURRENT
(A)
SCHOTTKY
DIODE
SLOPE: 1/RDIO(ON)
IMAX
VFWD
40853 F03
Figure 3. LTC4085-3 Schottky Diode vs Forward Voltage Drop
OPERATION
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相關代理商/技術參數(shù) |
參數(shù)描述 |
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| LTC4085EDE-4#PBF | 功能描述:IC USB POWER MANAGER 14DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 電池管理 系列:* 標準包裝:61 系列:- 功能:電源管理 電池化學:鋰離子（Li-Ion）、鋰聚合物（Li-Pol） 電源電壓:4.35 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:22-WFDFN 裸露焊盤 供應商設備封裝:22-DFN（6x3）裸露焊盤 包裝:管件 |
| LTC4085EDE-4#TRPBF | 功能描述:IC USB POWER MANAGER 14DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 電池管理 系列:* 標準包裝:61 系列:- 功能:電源管理 電池化學:鋰離子（Li-Ion）、鋰聚合物（Li-Pol） 電源電壓:4.35 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:22-WFDFN 裸露焊盤 供應商設備封裝:22-DFN（6x3）裸露焊盤 包裝:管件 |
| LTC4085EDEPBF | 制造商:Linear Technology 功能描述:Li-Ion Charger + USB Power Mgr LTC4085 |
| LTC4085EDE-PBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:USB Power Manager with Ideal Diode Controller and Li-Ion Charger |
| LTC4085EDE-TRPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:USB Power Manager with Ideal Diode Controller and Li-Ion Charger |
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