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參數(shù)資料
| 型號(hào)： | LTC4071EMS8E#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)： | 3/18頁 |
| 文件大?。?/td> | 219K |
| 代理商： | LTC4071EMS8E#TRPBF |
LTC4071
11
4071fb
applicaTions inForMaTion
The GND pin of the top device is simply connected to
the VCC pin of the bottom device. Care must be taken in
observing the HBO status output pin of the top device as
this signal is no longer ground referenced. Likewise for
the control inputs of the top device; tie ADJ and LBSEL
of the top device to the local GND or VCC pins. Also, the
wall adapter must have a high enough voltage rating to
charge both cells.
NTC Protection
TheLTC4071measuresbatterytemperaturewithanegative
temperaturecoefficientthermistorthermallycoupledtothe
battery.NTCthermistorshavetemperaturecharacteristics
which are specified in resistance-temperature conversion
tables. Internal NTC circuitry protects the battery from
excessive heat by reducing the float voltage for each
10°C rise in temperature above 40°C (assuming a Vishay
thermistor with a B25/85 value of 3490).
The LTC4071 uses a ratio of resistor values to measure
battery temperature. The LTC4071 contains an internal
fixed resistor voltage divider from NTCBIAS to GND with
four tap points; NTCTH1–NTCTH4. The voltages at these
tap points are periodically compared against the voltage at
the NTC pin to measure battery temperature. To conserve
power, the battery temperature is measured periodically
by biasing the NTCBIAS pin to VCC about once every 1.5
seconds.
The voltage at the NTC pin depends on the ratio of 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 when it is pulsed to VCC 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 a different B25/85 value may also
be used with the LTC4071. 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 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, e.g. NTHS0402N01N1003F, at 70°C (with
RNOM = 100k) choose RFIX = 3.92k. The temperature trip
points are found by looking up the curve 1 thermistor R/T
values plus RFIX that correspond to the ratios for NTCTH1
= 36.5%, NTCTH2 = 29%, 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 ad-
ditional component. Instead decrease RNOM to adjust the
NTCTH thresholds for a given R/T thermistor profile. For
example, if RNOM = 88.7k (with the same 100k thermis-
tor) then the temperature trip points are 41.0°C, 49.8°C,
58.5°C and 67.3°C.
WhenusingtheNTCfeaturesoftheLTC4071itisimportant
to keep in mind that the maximum shunt current increases
asthefloatvoltage,VFLOAT_EFFdropswithNTCconditioning.
Reviewing the single-cell battery charger application with
a 12V wall adapter in Figure 2; the input resistor should be
increased to 165 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 LTC4071 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 θJA 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 θJA of 76°C/W in the DFN package, at maximum
shunt current of 50mA the junction temperature rise is
about 16°C above ambient. The junction temperature, TJ,
iscalculateddependingonambienttemperature,TA,power
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| LTC4071IDDB | 制造商:LINEAR 制造商全稱:LINEAR 功能描述:Li-Ion/Polymer Shunt Battery Charger System with Low Battery Disconnect |
| LTC4071IDDB#PBF | 制造商:Linear Technology 功能描述:Battery Charger Li-Ion/Li-Polymer 50mA 8-Pin DFN EP |
| LTC4071IDDB#TRPBF | 功能描述:IC LI-ION/POLY BATT CHRGR 8-DFN RoHS:是 類別:集成電路 (IC) >> PMIC - 電池管理 系列:- 標(biāo)準(zhǔn)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 |
| LTC4071IMS8E | 制造商:LINEAR 制造商全稱:LINEAR 功能描述:Li-Ion/Polymer Shunt Battery Charger System with Low Battery Disconnect |
| LTC4071IMS8E#PBF | 功能描述:IC LI-ION/POLY BATT CHRGR 8-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 電池管理 系列:- 標(biāo)準(zhǔn)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 |
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