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參數(shù)資料
| 型號： | LTC4070EMS8E#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 電源管理 |
| 英文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO8 |
| 封裝： | LEAD FREE, PLASTIC, MSOP-8 |
| 文件頁數(shù)： | 2/16頁 |
| 文件大?。?/td> | 214K |
| 代理商： | LTC4070EMS8E#TRPBF |
LTC4070
10
4070fc
applicaTions inForMaTion
The voltage at the NTC pin depends on the ratio of the NTC
thermistor value, RNTC, and a bias resistor, RNOM. Choose
RNOM equal to the value of the thermistor at 25°C. RNOM
is 10k for a Vishay NTHS0402N02N1002F thermistor with
a B25/85 value of 3490. RNOM must be connected from
NTCBIAS to NTC. The ratio of the NTC pin voltage to the
NTCBIAS voltage is:
RNTC
RNTC +RNOM
(
)
When the thermistor temperature rises, the resistance
drops; and the resistor divider between RNOM and the
thermistor lowers the voltage at the NTC pin.
An NTC thermistor with higher B25/85 values may also
be used with the LTC4070. However the temperature trip
points are shifted due to the higher negative temperature
coefficient of the thermistor. To correct for this difference
add a resistor, RFIX, in series with the higher B25/85 value
thermistor to shift the ratio,
RFIX +RNTC
RFIX +RNTC +RNOM
(
)
up to the internal resistive divider tap points: NTCTH1
through NTCTH4. For a 100k thermistor with a B25/85 value
of 3950 NTHS0402N01N1003F, at 70°C (with RNOM =
100k) choose RFIX = 3.92k. The temperature trip points
are found by looking up the thermistor R/T values plus
RFIX that correspond to the ratios for NTCTH1 = 36.5%,
NTCTH2 = 29.0%, NTCTH3 = 22.8%, and NTCTH4 = 17.8%.
Selecting RFIX = 3.92k results in trip points of 39.9°C,
49.4°C, 59.2°C and 69.6°C.
Another technique may be used without adding an
additional component. Instead decrease RNOM to adjust
theNTCTHthresholdsforagivenR/Tthermistorprofile.For
example, if RNOM = 88.7k (with the same 100k thermistor)
thenthetemperaturetrippointsare41.0°C,49.8°C,58.5°C,
and 67.3°C.
WhenusingtheNTCfeaturesoftheLTC4070itisimportant
to keep in mind that the maximum shunt current increases
asthefloatvoltage,VFLOAT_EFFdropswithNTCconditioning.
Reviewing the Typical Application with a 12V wall adapter
in Figure 1; the input resistor, RIN, should be increased
to 165Ω such that the maximum shunt current does not
exceed 50mA at the lowest possible float voltage due to
NTC conditioning, VFLOAT_MIN = 3.8V.
Thermal Considerations
At maximum shunt current, the LTC4070 may dissipate up
to 205mW. The thermal dissipation of the package should
be taken into account when operating at maximum shunt
current so as not to exceed the absolute maximum junc-
tion temperature of the device. With qJA of 40°C/W, in the
MSOP package, at maximum shunt current of 50mA the
junction temperature rise is about 8°C above ambient.
With qJA of 76°C/W in the DFN package, at maximum
shunt current of 50mA the junction temperature rise is
about 16°C above ambient.
Operation with an External PFET to Boost Shunt Current
Table 2 lists recommended devices to increase the
maximum shunt current. Due to the requirement for low
capacitance on the DRV pin node, it is recommended that
only low gate charge and high threshold PFET devices be
used. Also it is recommended that careful PCB layout be
used to keep leakage at the DRV pin to a minimum as the
IDRV(SINK) current is typically 3A.
Refer to device manufacturers data sheets for maximum
continuouspowerdissipationandthermalresistancewhen
selecting an external PFET for a particular application.
Table 2. Recommended External Shunt PFETS
DEVICE
VENDOR
QGS
VTH(MIN)
RDS(ON)
FDN352AP
Fairchild
0.50nC
–0.8V
0.33
Si3467DV
Vishay
1.7nC
–1.0V
0.073
Si3469DV
Vishay
3.8nC
–1.0V
0.041
DMP2130LDM
Diodes Inc.
2.0nC
–0.6V
0.094
DMP3015LSS
Diodes Inc.
7.2nC
–1.0V
0.014
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LTC4070IDDB | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Li-Ion/Polymer Shunt Battery Charger System |
| LTC4070IDDB#PBF | 制造商:Linear Technology 功能描述: |
| LTC4070IDDB#TRMPBF | 功能描述:IC BATT CHRGR LIION/POLY 8DFN 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(xué):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(yīng)商設(shè)備封裝:22-DFN（6x3）裸露焊盤 包裝:管件 |
| LTC4070IDDB#TRPBF | 功能描述:IC BATT CHRGR LIION/POLY 8DFN 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(xué):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(yīng)商設(shè)備封裝:22-DFN（6x3）裸露焊盤 包裝:管件 |
| LTC4070IDDBPBF | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Li-Ion/Polymer Shunt Battery Charger System |
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